28594755032

Committed 02 Jul 2026 01:42PM UTC coverage: 89.0% (-0.08%) from 89.08%

Build # 28594755032

Build Type

Pull #253

github

Committed by

orneryd

Commit Message

addressing PR feedback, fix pruning, namespace leak, cleaning up key parsing

Pull Request Pull Request #253: feat(cypher,storage): adding adjacency snapshot isolation api

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/pkg/cypher/executor.go

// Package cypher provides Neo4j-compatible Cypher query execution for NornicDB.
//
// This package implements a Cypher query parser and executor that supports
// the core Neo4j Cypher query language features. It enables NornicDB to be
// compatible with existing Neo4j applications and tools.
//
// Supported Cypher Features:
//   - MATCH: Pattern matching with node and relationship patterns
//   - CREATE: Creating nodes and relationships
//   - MERGE: Upsert operations with ON CREATE/ON MATCH clauses
//   - DELETE/DETACH DELETE: Removing nodes and relationships
//   - SET: Updating node and relationship properties
//   - REMOVE: Removing properties and labels
//   - RETURN: Returning query results
//   - WHERE: Filtering with conditions
//   - WITH: Passing results between query parts
//   - OPTIONAL MATCH: Left outer joins
//   - CALL: Procedure calls
//   - UNWIND: List expansion
//
// Example Usage:
//
//        // Create executor with storage backend
//        storage := storage.NewMemoryEngine()
//        executor := cypher.NewStorageExecutor(storage)
//
//        // Execute Cypher queries
//        result, err := executor.Execute(ctx, "CREATE (n:Person {name: 'Alice', age: 30})", nil)
//        if err != nil {
//                log.Fatal(err)
//        }
//
//        // Query with parameters
//        params := map[string]interface{}{
//                "name": "Alice",
//                "minAge": 25,
//        }
//        result, err = executor.Execute(ctx,
//                "MATCH (n:Person {name: $name}) WHERE n.age >= $minAge RETURN n", params)
//
//        // Complex query with relationships
//        result, err = executor.Execute(ctx, `
//                MATCH (a:Person)-[r:KNOWS]->(b:Person)
//                WHERE a.age > 25
//                RETURN a.name, r.since, b.name
//                ORDER BY a.age DESC
//                LIMIT 10
//        `, nil)
//
//        // Process results
//        for _, row := range result.Rows {
//                // process row (e.g. emit "Row: %v" via the configured logger)
//        }
//
// Neo4j Compatibility:
//
// The executor aims for high compatibility with Neo4j Cypher:
//   - Same syntax and semantics for core operations
//   - Parameter substitution with $param syntax
//   - Neo4j-style error messages and codes
//   - Compatible result format for drivers
//   - Support for Neo4j built-in functions
//
// Query Processing Pipeline:
//
// 1. **Parsing**: Query is parsed into an AST (Abstract Syntax Tree)
// 2. **Validation**: Syntax and semantic validation
// 3. **Parameter Substitution**: Replace $param with actual values
// 4. **Execution Planning**: Determine optimal execution strategy
// 5. **Execution**: Execute against storage backend
// 6. **Result Formatting**: Format results for Neo4j compatibility
//
// Performance Considerations:
//
//   - Pattern matching is optimized for common cases
//   - Indexes are used automatically when available
//   - Query planning chooses efficient execution paths
//   - Bulk operations are optimized for large datasets
//
// Limitations:
//
// Current limitations compared to full Neo4j:
//   - No user-defined procedures (CALL is limited to built-ins)
//   - No complex path expressions
//   - No graph algorithms (shortest path, etc.)
//   - No schema constraints (handled by storage layer)
//   - No transactions (single-query atomicity only)
//
// ELI12 (Explain Like I'm 12):
//
// Think of Cypher like asking questions about a social network:
//
//  1. **MATCH**: "Find all people named Alice" - like searching through
//     a phone book for everyone with a specific name.
//
//  2. **CREATE**: "Add a new person named Bob" - like writing a new
//     entry in the phone book.
//
//  3. **Relationships**: "Find who Alice knows" - like following the
//     lines between people on a friendship map.
//
//  4. **WHERE**: "Find people older than 25" - like adding a filter
//     to only show certain results.
//
//  5. **RETURN**: "Show me their names and ages" - like deciding which
//     information to display from your search.
//
// The Cypher executor is like a smart assistant that understands these
// questions and knows how to find the answers in your data!
package cypher

import (
        "context"
        "errors"
        "fmt"
        "io"
        "log/slog"
        "strconv"
        "strings"
        "sync"
        "time"
        "unicode"

        "github.com/orneryd/nornicdb/pkg/config"
        "github.com/orneryd/nornicdb/pkg/cypher/antlr"
        "github.com/orneryd/nornicdb/pkg/embeddingutil"
        nornicerrors "github.com/orneryd/nornicdb/pkg/errors"
        "github.com/orneryd/nornicdb/pkg/fabric"
        "github.com/orneryd/nornicdb/pkg/heimdall"
        "github.com/orneryd/nornicdb/pkg/observability"
        "github.com/orneryd/nornicdb/pkg/search"
        "github.com/orneryd/nornicdb/pkg/storage"
        "github.com/orneryd/nornicdb/pkg/vectorspace"
        "go.opentelemetry.io/otel/attribute"
)

// Subquery detection tags. Routing uses scanner helpers below rather than regex.
const (
        existsSubqueryRe    = "EXISTS"
        notExistsSubqueryRe = "NOT EXISTS"
        countSubqueryRe     = "COUNT"
        callSubqueryRe      = "CALL"
        collectSubqueryRe   = "COLLECT"
)

// hasSubqueryPattern checks if the query contains a subquery pattern (keyword + optional whitespace + brace)
func hasSubqueryPattern(query string, pattern string) bool {
        switch pattern {
        case existsSubqueryRe:
                return hasKeywordFollowedByBrace(query, "EXISTS")
        case notExistsSubqueryRe:
                return hasNotExistsFollowedByBrace(query)
        case countSubqueryRe:
                return hasKeywordFollowedByBrace(query, "COUNT")
        case callSubqueryRe:
                return hasCallSubqueryPattern(query)
        case collectSubqueryRe:
                return hasKeywordFollowedByBrace(query, "COLLECT")
        }
        return false
}

func hasCallSubqueryPattern(query string) bool {
        for i := 0; i < len(query); i++ {
                if !matchKeywordAt(query, i, "CALL") {
                        continue
                }
                j := skipSpaces(query, i+len("CALL"))
                if j < len(query) && query[j] == '{' {
                        return true
                }
                if j >= len(query) || query[j] != '(' {
                        continue
                }
                close := findMatchingCallParen(query, j)
                if close < 0 {
                        continue
                }
                k := skipSpaces(query, close+1)
                if k < len(query) && query[k] == '{' {
                        return true
                }
        }
        return false
}

func hasCallInTransactions(query string) bool {
        return hasCallSubqueryPattern(query) && findKeywordIndex(query, "IN TRANSACTIONS") >= 0
}

func hasNotExistsFollowedByBrace(query string) bool {
        for i := 0; i < len(query); i++ {
                if !matchKeywordAt(query, i, "NOT") {
                        continue
                }
                j := skipSpaces(query, i+3)
                if !matchKeywordAt(query, j, "EXISTS") {
                        continue
                }
                k := skipSpaces(query, j+6)
                if k < len(query) && query[k] == '{' {
                        return true
                }
        }
        return false
}

func hasKeywordFollowedByBrace(query, keyword string) bool {
        kwLen := len(keyword)
        for i := 0; i < len(query); i++ {
                if !matchKeywordAt(query, i, keyword) {
                        continue
                }
                j := skipSpaces(query, i+kwLen)
                if j < len(query) && query[j] == '{' {
                        return true
                }
        }
        return false
}

func skipSpaces(s string, i int) int {
        for i < len(s) {
                switch s[i] {
                case ' ', '\t', '\n', '\r':
                        i++
                default:
                        return i
                }
        }
        return i
}

func matchKeywordAt(s string, i int, keyword string) bool {
        if i < 0 || i+len(keyword) > len(s) {
                return false
        }
        if i > 0 && isIdentCharByte(s[i-1]) {
                return false
        }
        if i+len(keyword) < len(s) && isIdentCharByte(s[i+len(keyword)]) {
                return false
        }
        return strings.EqualFold(s[i:i+len(keyword)], keyword)
}

func isIdentCharByte(b byte) bool {
        return b == '_' || (b >= 'a' && b <= 'z') || (b >= 'A' && b <= 'Z') || (b >= '0' && b <= '9')
}

// StorageExecutor executes Cypher queries against a storage backend.
//
// The StorageExecutor provides the main interface for executing Cypher queries
// in NornicDB. It handles query parsing, validation, parameter substitution,
// and execution against the underlying storage engine.
//
// Key features:
//   - Neo4j-compatible Cypher syntax support
//   - Parameter substitution with $param syntax
//   - Query validation and error reporting
//   - Optimized execution planning
//   - Thread-safe concurrent execution
//
// Example:
//
//        storage := storage.NewMemoryEngine()
//        executor := cypher.NewStorageExecutor(storage)
//
//        // Simple node creation
//        result, _ := executor.Execute(ctx, "CREATE (n:Person {name: 'Alice'})", nil)
//
//        // Parameterized query
//        params := map[string]interface{}{"name": "Bob", "age": 30}
//        result, _ = executor.Execute(ctx,
//                "CREATE (n:Person {name: $name, age: $age})", params)
//
//        // Complex pattern matching
//        result, _ = executor.Execute(ctx, `
//                MATCH (a:Person)-[:KNOWS]->(b:Person)
//                WHERE a.age > 25
//                RETURN a.name, b.name
//        `, nil)
//
// Thread Safety:
//
//        The executor is thread-safe and can handle concurrent queries.
//
// NodeMutatedCallback is called when a node is created or mutated via Cypher (CREATE, MERGE, SET, REMOVE, or procedures that update nodes).
// This allows external systems (like the embed queue) to be notified so embeddings can be (re)generated.
type NodeMutatedCallback func(nodeID string)

type StorageExecutor struct {
        parser    *Parser
        storage   storage.Engine
        txContext *TransactionContext // Active transaction context
        cache     *SmartQueryCache    // Query result cache with label-aware invalidation
        planCache *QueryPlanCache     // Parsed query plan cache
        // fabricPlanCache caches planned Fabric fragment trees (query + sessionDB).
        fabricPlanCache *fabric.PlanCache
        analyzer        *QueryAnalyzer // Query analysis with AST caching

        // Node lookup cache for MATCH patterns like (n:Label {prop: value})
        // Key: "Label:{prop:value,...}", Value: *storage.Node
        // This dramatically speeds up repeated MATCH lookups for the same pattern.
        //
        // Transaction scoping: cloneWithStorage gives transactional clones a
        // FRESH cache + mutex so concurrent transactions can't see each other's
        // uncommitted MERGE node-ID mappings. Without that scoping, two writers
        // MERGE-ing on the same (label, prop, value) would each populate the
        // shared cache pre-commit; the peer would then probe its own
        // tx.badgerTx for the cached uncommitted node ID, taking the peer's
        // node key into its read set, and Badger SSI would reject the loser
        // with "Transaction Conflict" instead of the consumer-pinned
        // commit-time UNIQUE shape.
        nodeLookupCache   map[string]*storage.Node
        nodeLookupCacheMu *sync.RWMutex

        // deferFlush when true, writes are not auto-flushed (Bolt layer handles it)
        deferFlush bool

        // embedder for server-side query embedding (optional)
        // If set, vector search can accept string queries which are embedded automatically
        embedder QueryEmbedder

        // searchService optionally provides unified search semantics for Cypher procedures.
        // When set, db.index.vector.queryNodes delegates to search.Service.
        searchService *search.Service

        // inferenceManager optionally provides LLM inference for db.infer.
        inferenceManager InferenceManager

        // onNodeMutated is called when a node is created or mutated (CREATE, MERGE, SET, REMOVE).
        // This allows the embed queue to be notified so embeddings are (re)generated.
        onNodeMutated               NodeMutatedCallback
        inlineEmbeddingTextOptions  *embeddingutil.EmbedTextOptions
        inlineEmbeddingChunkSize    int
        inlineEmbeddingChunkOverlap int

        // defaultEmbeddingDimensions is the configured embedding dimensions for vector indexes
        // Used as default when CREATE VECTOR INDEX doesn't specify dimensions
        defaultEmbeddingDimensions int

        // dbManager is optional - when set, enables system commands (CREATE/DROP/SHOW DATABASE)
        // System commands require DatabaseManager to manage multiple databases
        // This is an interface to avoid import cycles with multidb package
        dbManager DatabaseManagerInterface

        // shellParams stores Neo4j shell-style parameters set via :param / :params.
        // These are session-scoped to the executor instance and merged with per-call params.
        shellParams   map[string]interface{}
        shellParamsMu sync.RWMutex

        // vectorRegistry maps Cypher vector index definitions to concrete vector spaces.
        vectorRegistry    *vectorspace.IndexRegistry
        vectorIndexSpaces map[string]vectorspace.VectorSpaceKey
        // fabricRecordBindings carries correlated APPLY input bindings for Fabric execution.
        // It is set only on per-query cloned executors.
        fabricRecordBindings map[string]interface{}

        decayMismatchLogged bool
        hotPathTraceState   *hotPathTraceState

        // vectorQueryEmbedCache caches server-side embeddings for db.index.vector.queryNodes/
        // queryRelationships string-input mode to avoid repeated embedding latency.
        // Key is canonicalized (case/whitespace normalized) query text.
        vectorQueryEmbedCache map[string][]float32
        // vectorQueryEmbedInflight de-duplicates concurrent embedding work per key.
        vectorQueryEmbedInflight map[string]*vectorEmbedInflight
        vectorQueryEmbedMu       sync.Mutex

        // unwindMergeChainPlanCache memoizes parsed plans for the generalized
        // UNWIND ... MERGE batch hot path keyed by mutation query text.
        unwindMergeChainPlanCache *unwindMergeChainPlanCache
        // upperQueryCache memoizes uppercase routing forms for exact query text
        // to avoid repeated strings.ToUpper allocations on hot query shapes.
        //
        // Initialized lazily via upperQueryCacheOnce so concurrent CALL { ... }
        // subqueries that share an executor pointer don't race on the lazy
        // install. See ensureUpperQueryCache for the matching helper.
        upperQueryCache     *upperQueryCache
        upperQueryCacheOnce sync.Once
        // syntaxValidationCache memoizes successful Nornic-parser syntax checks
        // for exact query text to avoid repeated bracket/string scans on hot loops.
        //
        // The cache pointer is lazily installed via syntaxValidationOnce so that
        // concurrent callers in parallel CALL { ... } / executeCallTailParallel
        // do not race on the pointer write — the goroutine fanout in call.go
        // previously triggered a data race detected by `go test -race`.
        syntaxValidationCache *syntaxValidationCache
        syntaxValidationOnce  sync.Once

        // log is the structured logger used for slow-query and operational log
        // emission. Threaded via SetLogger after construction (D-01 non-breaking
        // pattern — NewStorageExecutor signature unchanged). Nil-safe via the
        // internal logger() helper which lazily installs a discard fallback.
        log *slog.Logger

        // slowQueryThreshold gates the D-04c slow-query emission path. Zero or
        // negative values disable slow-query logging entirely. Set via
        // SetSlowQueryThreshold so the configured cfg.Logging.SlowQueryThreshold
        // flows in from the bootstrap site without breaking the ctor.
        slowQueryThreshold time.Duration

        // metrics is the Plan 04-03 CypherMetrics typed bag (MET-08). Injected
        // post-construction via SetCypherMetrics (D-01 non-breaking pattern,
        // mirrors SetLogger / SetSlowQueryThreshold). Nil-safe: the
        // observe* helpers no-op when metrics is nil so tests and alternate
        // constructors don't have to wire it.
        metrics *observability.CypherMetrics

        // database is the tenant identifier passed as the `database` label
        // on tenant-tagged Cypher families when D-08 tenantLabelsEnabled=true.
        // Empty string is acceptable when the bag was constructed with the
        // tenant flag off — Bind helpers drop the arg internally.
        database string
}

type unwindMergeChainPlanCache struct {
        mu    sync.RWMutex
        plans map[string]unwindMergeChainPlan
}

type upperQueryCache struct {
        mu    sync.RWMutex
        cache map[string]string
        max   int
}

type syntaxValidationCache struct {
        mu    sync.RWMutex
        cache map[string]struct{}
        max   int
}

func (e *StorageExecutor) cloneWithStorage(override storage.Engine) *StorageExecutor {
        e.ensureNodeLookupCache()
        // Transactional clones use the lookup cache pinned to the
        // transactionStorageWrapper. Concurrent transactions hold distinct
        // wrappers and therefore distinct caches — that isolation prevents
        // a peer's uncommitted node-ID mapping from leaking into this
        // transaction's tx.badgerTx read set (and corrupting Badger SSI
        // conflict shapes). Re-entrant Execute calls within the same
        // transaction reuse the wrapper, so the in-tx cache survives
        // across clauses. On successful commit, callers promote the
        // wrapper-scoped entries back into the parent executor via
        // promoteNodeLookupCacheTo so subsequent Execute calls still
        // benefit from the cross-query speedup.
        lookupCache := e.nodeLookupCache
        lookupCacheMu := e.nodeLookupCacheLock()
        if txWrapper, isTxScoped := override.(*transactionStorageWrapper); isTxScoped {
                // Seed the wrapper-scoped cache from the parent's committed
                // entries on first clone so subsequent Execute calls retain
                // the cross-query speedup. Concurrent transactions still hold
                // distinct wrappers — the seeding is a one-shot copy, not a
                // live alias, so peer-tx writes after this point cannot leak.
                txWrapper.ensureNodeLookupCacheLocked(e)
                lookupCache = txWrapper.txNodeLookupCache
                lookupCacheMu = txWrapper.txNodeLookupCacheMu
        }
        return &StorageExecutor{
                parser:                      e.parser,
                storage:                     override,
                txContext:                   e.txContext,
                cache:                       e.cache,
                planCache:                   e.planCache,
                fabricPlanCache:             e.fabricPlanCache,
                analyzer:                    e.analyzer,
                nodeLookupCache:             lookupCache,
                nodeLookupCacheMu:           lookupCacheMu,
                deferFlush:                  e.deferFlush,
                embedder:                    e.embedder,
                searchService:               e.searchService,
                inferenceManager:            e.inferenceManager,
                onNodeMutated:               e.onNodeMutated,
                inlineEmbeddingTextOptions:  e.inlineEmbeddingTextOptions,
                inlineEmbeddingChunkSize:    e.inlineEmbeddingChunkSize,
                inlineEmbeddingChunkOverlap: e.inlineEmbeddingChunkOverlap,
                defaultEmbeddingDimensions:  e.defaultEmbeddingDimensions,
                dbManager:                   e.dbManager,
                shellParams:                 e.shellParams,
                vectorRegistry:              e.vectorRegistry,
                vectorIndexSpaces:           e.vectorIndexSpaces,
                fabricRecordBindings:        e.fabricRecordBindings,
                hotPathTraceState:           e.hotPathTraceState,
                vectorQueryEmbedCache:       e.vectorQueryEmbedCache,
                vectorQueryEmbedInflight:    e.vectorQueryEmbedInflight,
                unwindMergeChainPlanCache:   e.unwindMergeChainPlanCache,
                upperQueryCache:             e.upperQueryCache,
                syntaxValidationCache:       e.syntaxValidationCache,
                // Plan 04-03: propagate the metrics bag + database label through
                // per-query / per-storage clones so observation chokepoints in
                // Execute() see the same bag regardless of clone depth.
                metrics:  e.metrics,
                database: e.database,
        }
}

func (e *StorageExecutor) nodeLookupCacheLock() *sync.RWMutex {
        if e.nodeLookupCacheMu == nil {
                e.nodeLookupCacheMu = &sync.RWMutex{}
        }
        return e.nodeLookupCacheMu
}

func (e *StorageExecutor) ensureNodeLookupCache() {
        cacheMu := e.nodeLookupCacheLock()
        cacheMu.Lock()
        defer cacheMu.Unlock()
        if e.nodeLookupCache == nil {
                e.nodeLookupCache = make(map[string]*storage.Node, 1000)
        }
}

type vectorEmbedInflight struct {
        done chan struct{}
        vec  []float32
        err  error
}

type hotPathTraceState struct {
        mu    sync.RWMutex
        trace HotPathTrace
}

// DatabaseManagerInterface is a minimal interface to avoid import cycles with multidb package.
// This allows the executor to call database management operations without directly
// depending on the multidb package.
type DatabaseManagerInterface interface {
        CreateDatabase(name string) error
        DropDatabase(name string) error
        ListDatabases() []DatabaseInfoInterface
        Exists(name string) bool
        CreateAlias(alias, databaseName string) error
        DropAlias(alias string) error
        ListAliases(databaseName string) map[string]string
        ResolveDatabase(nameOrAlias string) (string, error)
        SetDatabaseLimits(databaseName string, limits interface{}) error
        GetDatabaseLimits(databaseName string) (interface{}, error)
        // Composite database methods
        CreateCompositeDatabase(name string, constituents []interface{}) error
        DropCompositeDatabase(name string) error
        AddConstituent(compositeName string, constituent interface{}) error
        RemoveConstituent(compositeName string, alias string) error
        GetCompositeConstituents(compositeName string) ([]interface{}, error)
        ListCompositeDatabases() []DatabaseInfoInterface
        IsCompositeDatabase(name string) bool
        // GetStorageForUse returns the storage engine for a database, supporting
        // composite databases. authToken is forwarded for remote constituents.
        GetStorageForUse(name string, authToken string) (interface{}, error)
}

// DatabaseInfoInterface provides database metadata without importing multidb.
type DatabaseInfoInterface interface {
        Name() string
        Type() string
        Status() string
        IsDefault() bool
        CreatedAt() time.Time
}

// QueryEmbedder generates embeddings for search queries.
// This is a minimal interface to avoid import cycles with embed package.
type QueryEmbedder interface {
        Embed(ctx context.Context, text string) ([]float32, error)
        ChunkText(text string, maxTokens, overlap int) ([]string, error)
}

// InferenceManager is the minimal LLM contract used by Cypher db.infer.
// It mirrors Heimdall manager methods to keep adapters thin.
type InferenceManager interface {
        Generate(ctx context.Context, prompt string, params heimdall.GenerateParams) (string, error)
        Chat(ctx context.Context, req heimdall.ChatRequest) (*heimdall.ChatResponse, error)
}

// NewStorageExecutor creates a new Cypher executor with the given storage backend.
//
// The executor is initialized with a parser and connected to the storage engine.
// It's ready to execute Cypher queries immediately after creation.
//
// Parameters:
//   - store: Storage engine to execute queries against (required)
//
// Returns:
//   - StorageExecutor ready for query execution
//
// Example:
//
//        // Create storage and executor
//        storage := storage.NewMemoryEngine()
//        executor := cypher.NewStorageExecutor(storage)
//
//        // Executor is ready for queries
//        result, err := executor.Execute(ctx, "MATCH (n) RETURN count(n)", nil)
func NewStorageExecutor(store storage.Engine) *StorageExecutor {
        exec := &StorageExecutor{
                parser:                      NewParser(),
                storage:                     store,
                cache:                       NewSmartQueryCache(1000), // Query result cache with label-aware invalidation
                planCache:                   NewQueryPlanCache(500),   // Cache 500 parsed query plans
                fabricPlanCache:             fabric.NewPlanCache(500), // Cache 500 Fabric fragment plans
                analyzer:                    NewQueryAnalyzer(1000),   // Cache 1000 parsed query ASTs
                nodeLookupCache:             make(map[string]*storage.Node, 1000),
                nodeLookupCacheMu:           &sync.RWMutex{},
                shellParams:                 make(map[string]interface{}),
                searchService:               nil, // Lazy initialization - will be set via SetSearchService() to reuse DB's cached service
                vectorRegistry:              vectorspace.NewIndexRegistry(),
                vectorIndexSpaces:           make(map[string]vectorspace.VectorSpaceKey),
                hotPathTraceState:           &hotPathTraceState{},
                vectorQueryEmbedCache:       make(map[string][]float32, 512),
                vectorQueryEmbedInflight:    make(map[string]*vectorEmbedInflight, 64),
                unwindMergeChainPlanCache:   &unwindMergeChainPlanCache{plans: make(map[string]unwindMergeChainPlan, 128)},
                inlineEmbeddingTextOptions:  embeddingutil.EmbedTextOptionsFromConfig(config.LoadFromEnv()),
                inlineEmbeddingChunkSize:    maxInt(config.LoadFromEnv().EmbeddingWorker.ChunkSize, 1),
                inlineEmbeddingChunkOverlap: maxInt(config.LoadFromEnv().EmbeddingWorker.ChunkOverlap, 0),
        }
        ensureBuiltInProceduresRegistered()
        _ = exec.loadPersistedProcedures()
        return exec
}

// ClearQueryCaches clears executor-local caches that can retain stale read results.
func (e *StorageExecutor) ClearQueryCaches() {
        if e.cache != nil {
                e.cache.Invalidate()
        }
        if e.planCache != nil {
                e.planCache.Clear()
        }
        if e.analyzer != nil {
                e.analyzer.ClearCache()
        }
        cacheMu := e.nodeLookupCacheLock()
        cacheMu.Lock()
        e.nodeLookupCache = make(map[string]*storage.Node, 1000)
        cacheMu.Unlock()
}

// InvalidateEntityCaches evicts targeted cache entries affected by a specific entity state change.
func (e *StorageExecutor) InvalidateEntityCaches(entityID string, tokens []string) {
        if e.cache != nil && len(tokens) > 0 {
                e.cache.InvalidateLabels(tokens)
        }
        e.invalidateNodeLookupCacheForEntityID(storage.NodeID(entityID))
}

func (e *StorageExecutor) invalidateNodeLookupCacheForEntityID(entityID storage.NodeID) {
        if entityID == "" {
                return
        }
        cacheMu := e.nodeLookupCacheLock()
        cacheMu.Lock()
        for key, node := range e.nodeLookupCache {
                if node != nil && node.ID == entityID {
                        delete(e.nodeLookupCache, key)
                }
        }
        cacheMu.Unlock()
}

// SetLogger installs the structured slog.Logger used for slow-query and
// operational records. D-01 non-breaking: NewStorageExecutor's signature is
// unchanged; callers (cmd/nornicdb/main.go) call SetLogger after construction
// so the *slog.Logger from observability.NewLogger flows through.
//
// Discard-fallback: passing nil installs a slog.Logger backed by io.Discard
// so subsequent log emissions cannot panic. The "component" attribute is
// pre-bound here (not per-call) to honor the RESEARCH "Per-call .With()
// allocation" anti-pattern.
func (e *StorageExecutor) SetLogger(logger *slog.Logger) {
        if logger == nil {
                logger = slog.New(slog.NewTextHandler(io.Discard, nil))
        }
        e.log = logger.With("component", "cypher")
}

// SetSlowQueryThreshold configures the D-04c slow-query emission gate.
// Zero or negative durations disable slow-query logging entirely. Threaded
// from cfg.Logging.SlowQueryThreshold at the bootstrap site.
func (e *StorageExecutor) SetSlowQueryThreshold(d time.Duration) {
        e.slowQueryThreshold = d
}

// Logger returns the bound *slog.Logger. Exposed so transient executors
// (e.g., per-transaction sessions cloned from a base) can inherit the
// configured logger without re-threading from main.
func (e *StorageExecutor) Logger() *slog.Logger { return e.logger() }

// SlowQueryThreshold returns the configured slow-query emission gate.
// Exposed so cloned executors inherit the threshold from their base.
func (e *StorageExecutor) SlowQueryThreshold() time.Duration { return e.slowQueryThreshold }

// SetCypherMetrics installs the Plan 04-03 CypherMetrics typed bag (MET-08)
// and the database label value passed on tenant-tagged families when D-08
// tenantLabelsEnabled=true. Mirrors the SetLogger / SetSlowQueryThreshold
// non-breaking pattern (D-01 non-breaking ctor).
//
// Also propagates the bag into the executor's owned planCache so the
// planner_cache_{hits,misses,size} families fire from QueryPlanCache.Get/Put
// without callers having to reach into private fields.
//
// Nil-safe: passing m=nil leaves observation as a no-op so tests and
// alternate constructors that don't wire metrics don't have to. The three
// observation chokepoints in Execute() guard on m == nil.
//
// Cloned executors inherit metrics + database via cloneWithStorage so the
// bag flows through per-query / per-tx scoped clones.
func (e *StorageExecutor) SetCypherMetrics(m *observability.CypherMetrics, database string) {
        e.metrics = m
        e.database = database
        // D-12a planner cache wiring: propagate into the owned planCache so
        // the cypher subsystem's planner_cache_{hits,misses,size} families
        // observe automatically.
        if e.planCache != nil {
                e.planCache.SetCypherMetrics(m)
        }
}

// SetCacheMetrics installs the Plan 04-01 cross-cutting CacheMetrics bag
// for D-12a query-result cache observation. Routes the bag into the owned
// SmartQueryCache so cache_hits_total{cache="query_result"} +
// cache_misses_total + cache_evictions_total emit on every Get/Put/Evict.
//
// Nil-safe; mirrors SetCypherMetrics shape.
func (e *StorageExecutor) SetCacheMetrics(m *observability.CacheMetrics) {
        if e.cache != nil {
                e.cache.SetCacheMetrics(m)
        }
}

// CypherMetrics returns the injected metrics bag (or nil if unset). Exposed
// so cloned executors can re-inject when constructed via newTxScopedExecutor
// outside the cloneWithStorage pathway.
func (e *StorageExecutor) CypherMetrics() *observability.CypherMetrics { return e.metrics }

// Database returns the configured database label value used for tenant-tagged
// Cypher metric observations (D-08).
func (e *StorageExecutor) Database() string { return e.database }

// observeQuery is the single Cypher-side observation helper. Called at the
// three RISK-1 corrected chokepoints in Execute():
//
//        Site 1 — admin dispatch       (op_type="admin",       observeDuration=true)
//        Site 2 — parse-error          (op_type="parse_error", observeDuration=false)
//        Site 3 — normal-path-after-Analyze (op_type from classifyOpType, observeDuration=true)
//
// Nil-safe: no-ops when e.metrics is nil. Hot-path-cheap: per-call Bind via
// the bag's BindQueryDuration helper (one WithLabelValues lookup); future
// optimization can hoist Bind into struct fields cached at SetCypherMetrics
// time per MET-25 — see RowsReturned for the precedent. The current shape
// keeps SetCypherMetrics simple while still emitting via the typed bag.
func (e *StorageExecutor) observeQuery(opType string, observeDuration bool, start time.Time) {
        if e.metrics == nil {
                return
        }
        e.metrics.BindQueries(opType, e.database).Inc()
        if observeDuration {
                e.metrics.BindQueryDuration(opType, e.database).Observe(context.Background(), time.Since(start).Seconds())
        }
}

// observeTransactionConflict is the D-16 chokepoint helper: storage detects
// (returns storage.ErrConflict from the engine), Cypher counts (here, in the
// transaction-wrapper site that surfaces ErrConflict to the caller). Storage
// layer never imports observability — preserves AGENTS.md §8 separation.
//
// Nil-safe: no-ops when e.metrics is nil OR err is not ErrConflict OR err is
// nil. Defensive: errors.Is check rather than equality so wrapped errors
// (fmt.Errorf("...: %w", storage.ErrConflict)) still classify correctly.
func (e *StorageExecutor) observeTransactionConflict(err error) {
        if e.metrics == nil || err == nil {
                return
        }
        if !errors.Is(err, storage.ErrConflict) {
                return
        }
        e.metrics.BindTransactionConflicts(e.database).Inc()
}

// observeTransactionBegin increments the active_transactions gauge. Pair
// with observeTransactionEnd at every Commit/Rollback site so the gauge
// balances to 0 across normal, abort, and panic paths.
func (e *StorageExecutor) observeTransactionBegin() {
        if e.metrics == nil {
                return
        }
        e.metrics.ActiveTransactions.Inc()
}

// observeTransactionEnd decrements the active_transactions gauge. See
// observeTransactionBegin.
func (e *StorageExecutor) observeTransactionEnd() {
        if e.metrics == nil {
                return
        }
        e.metrics.ActiveTransactions.Dec()
}

// observeSlowQueryIfThresholded increments the slow_queries counter when
// duration meets the configured slowQueryThreshold (matches the Phase 2
// D-04c emitSlowQueryLog gate semantics: zero or negative threshold
// disables emission entirely).
func (e *StorageExecutor) observeSlowQueryIfThresholded(duration time.Duration) {
        if e.metrics == nil {
                return
        }
        if e.slowQueryThreshold <= 0 || duration < e.slowQueryThreshold {
                return
        }
        e.metrics.BindSlowQueries(e.database).Inc()
}

// logger returns the bound logger, lazily installing a discard fallback if
// SetLogger was never called. Internal — every emission site must read the
// logger via this helper, never via the stdlib package-level default
// (LOG-09 forbids that path).
func (e *StorageExecutor) logger() *slog.Logger {
        if e.log == nil {
                e.log = slog.New(slog.NewTextHandler(io.Discard, nil)).With("component", "cypher")
        }
        return e.log
}

// emitSlowQueryLog writes a single WARN record matching the LOG-07 schema
// when duration meets the configured threshold. RedactLiterals runs BEFORE
// truncation per D-04c so partial literals never leak via the truncation seam.
//
// Schema (D-04c):
//
//        level=WARN
//        msg="slow query"
//        event="slow_query"
//        plan_hash=<16-char hex from PlanHash; "0000000000000000" when plan is nil>
//        cypher.duration_ms=<int64 millisecond delta>
//        query=<RedactLiterals(query) truncated to 500 chars>
//
// Performance: PlanHash + RedactLiterals only fire when this method is called,
// i.e., only when the executor's measured duration exceeded the configured
// threshold. The hot path (Execute fast return) never enters this method.
func (e *StorageExecutor) emitSlowQueryLog(query string, plan *ExecutionPlan, duration time.Duration) {
        if e.slowQueryThreshold <= 0 || duration < e.slowQueryThreshold {
                return
        }
        redacted := RedactLiterals(query)
        if len(redacted) > 500 {
                redacted = redacted[:500]
        }
        e.logger().Warn("slow query",
                "event", "slow_query",
                "plan_hash", PlanHash(plan),
                "cypher.duration_ms", duration.Milliseconds(),
                "query", redacted,
        )
}

// SetDatabaseManager sets the database manager for system commands.
// When set, enables CREATE DATABASE, DROP DATABASE, and SHOW DATABASES commands.
//
// Example:
//
//        executor := cypher.NewStorageExecutor(storage)
//        executor.SetDatabaseManager(dbManager)
//        // Now CREATE DATABASE, DROP DATABASE, SHOW DATABASES work
func (e *StorageExecutor) SetDatabaseManager(dbManager DatabaseManagerInterface) {
        e.dbManager = dbManager
}

// SetEmbedder sets the query embedder for server-side embedding.
// When set, db.index.vector.queryNodes can accept string queries
// which are automatically embedded before search.
//
// Example:
//
//        executor := cypher.NewStorageExecutor(storage)
//        executor.SetEmbedder(embedder)
//
//        // Now vector search accepts both:
//        // CALL db.index.vector.queryNodes('idx', 10, [0.1, 0.2, ...])  // Vector
//        // CALL db.index.vector.queryNodes('idx', 10, 'search query')   // String (auto-embedded)
func (e *StorageExecutor) SetEmbedder(embedder QueryEmbedder) {
        e.embedder = embedder
        e.vectorQueryEmbedMu.Lock()
        e.vectorQueryEmbedCache = make(map[string][]float32, 512)
        e.vectorQueryEmbedInflight = make(map[string]*vectorEmbedInflight, 64)
        e.vectorQueryEmbedMu.Unlock()
}

// SetSearchService sets the unified search service used by Cypher procedures.
// When set, db.index.vector.queryNodes will delegate to search.Service.
func (e *StorageExecutor) SetSearchService(svc *search.Service) {
        e.searchService = svc
}

// SetInferenceManager sets the inference manager used by db.infer.
func (e *StorageExecutor) SetInferenceManager(mgr InferenceManager) {
        e.inferenceManager = mgr
}

// GetInferenceManager returns the configured inference manager.
func (e *StorageExecutor) GetInferenceManager() InferenceManager {
        return e.inferenceManager
}

// SetVectorRegistry allows wiring a shared index registry (e.g., per database).
// Defaults to an internal registry when not set.
func (e *StorageExecutor) SetVectorRegistry(reg *vectorspace.IndexRegistry) {
        if reg == nil {
                reg = vectorspace.NewIndexRegistry()
        }
        e.vectorRegistry = reg
}

// GetVectorRegistry exposes the current registry (for tests and adapters).
func (e *StorageExecutor) GetVectorRegistry() *vectorspace.IndexRegistry {
        return e.vectorRegistry
}

// GetEmbedder returns the query embedder if set.
// This allows copying the embedder to namespaced executors for GraphQL.
func (e *StorageExecutor) GetEmbedder() QueryEmbedder {
        return e.embedder
}

// SetNodeMutatedCallback sets a callback that is invoked when nodes are created
// or mutated (CREATE, MERGE, SET, REMOVE, or procedures that update nodes).
// This allows the embed queue to be notified so embeddings can be (re)generated.
//
// Example:
//
//        executor := cypher.NewStorageExecutor(storage)
//        executor.SetNodeMutatedCallback(func(nodeID string) {
//            embedQueue.Enqueue(nodeID)
//        })
func (e *StorageExecutor) SetNodeMutatedCallback(cb NodeMutatedCallback) {
        e.onNodeMutated = cb
}

// SetDefaultEmbeddingDimensions sets the default dimensions for vector indexes.
// This is used when CREATE VECTOR INDEX doesn't specify dimensions in OPTIONS.
func (e *StorageExecutor) SetDefaultEmbeddingDimensions(dims int) {
        e.defaultEmbeddingDimensions = dims
}

// GetDefaultEmbeddingDimensions returns the configured default embedding dimensions.
// Returns 1024 as fallback if not configured.
func (e *StorageExecutor) GetDefaultEmbeddingDimensions() int {
        return e.defaultEmbeddingDimensions
}

// notifyNodeMutated updates live search metadata and calls the onNodeMutated
// callback if set. Call after any node creation or mutation (CREATE, MERGE,
// SET, REMOVE) so search sees client-supplied vectors immediately and the
// embed queue can re-process.
func (e *StorageExecutor) notifyNodeMutated(nodeID string) {
        if e.searchService != nil && nodeID != "" {
                if node, err := e.storage.GetNode(storage.NodeID(nodeID)); err == nil && node != nil {
                        _ = e.searchService.IndexNode(node)
                }
        }
        if e.onNodeMutated != nil {
                e.onNodeMutated(nodeID)
        }
}

// notifyEdgeMutated updates live search metadata after a relationship create or
// mutation so relationship vector queries can use client-supplied vectors before
// a full search warmup/build has run.
func (e *StorageExecutor) notifyEdgeMutated(edgeID string) {
        if e.searchService == nil || edgeID == "" {
                return
        }
        if edge, err := e.storage.GetEdge(storage.EdgeID(edgeID)); err == nil && edge != nil {
                e.indexMutatedEdge(edge)
        }
}

func (e *StorageExecutor) indexMutatedEdge(edge *storage.Edge) {
        if e.searchService != nil && edge != nil {
                _ = e.searchService.IndexEdge(edge)
        }
}

// removeNodeFromSearch removes a node from the search service (vector/fulltext indexes).
// Call after successfully deleting a node via Cypher so embeddings are not left orphaned.
// nodeID may be prefixed (e.g. "nornic:xyz") or local ("xyz"); the search service expects local ID.
func (e *StorageExecutor) removeNodeFromSearch(nodeID string) {
        if e.searchService == nil || nodeID == "" {
                return
        }
        localID := nodeID
        if _, unprefixed, ok := storage.ParseDatabasePrefix(nodeID); ok {
                localID = unprefixed
        }
        _ = e.searchService.RemoveNode(storage.NodeID(localID))
}

// Flush persists all pending writes to storage.
// This implements FlushableExecutor for Bolt-level deferred commits.
func (e *StorageExecutor) Flush() error {
        if asyncEngine, ok := e.storage.(*storage.AsyncEngine); ok {
                return asyncEngine.Flush()
        }
        return nil
}

// SetDeferFlush enables/disables deferred flush mode.
// When enabled, writes are not auto-flushed - the Bolt layer calls Flush().
func (e *StorageExecutor) SetDeferFlush(enabled bool) {
        e.deferFlush = enabled
}

// queryDeletesNodes returns true if the query deletes nodes.
// Returns false for relationship-only deletes (CREATE rel...DELETE rel pattern).
func queryDeletesNodes(query string) bool {
        // DETACH DELETE always deletes nodes
        if strings.Contains(strings.ToUpper(query), "DETACH DELETE") {
                return true
        }
        // Relationship pattern (has -[...]-> or <-[...]-) with CREATE+DELETE = relationship delete only
        if strings.Contains(query, "]->(") || strings.Contains(query, ")<-[") {
                return false
        }
        return true
}

// Execute parses and executes a Cypher query with optional parameters.
//
// This is the main entry point for Cypher query execution. The method handles
// the complete query lifecycle: parsing, validation, parameter substitution,
// execution planning, and result formatting.
//
// Parameters:
//   - ctx: Context for cancellation and timeouts
//   - cypher: Cypher query string
//   - params: Optional parameters for $param substitution
//
// Returns:
//   - ExecuteResult with columns and rows
//   - Error if query parsing or execution fails
//
// Example:
//
//        // Simple query without parameters
//        result, err := executor.Execute(ctx, "MATCH (n:Person) RETURN n.name", nil)
//        if err != nil {
//                log.Fatal(err)
//        }
//
//        // Parameterized query
//        params := map[string]interface{}{
//                "name": "Alice",
//                "minAge": 25,
//        }
//        result, err = executor.Execute(ctx, `
//                MATCH (n:Person {name: $name})
//                WHERE n.age >= $minAge
//                RETURN n.name, n.age
//        `, params)
//
//        // Process results
//        // emit "Columns: %v" via the configured logger
//        for _, row := range result.Rows {
//                // process row (e.g. emit "Row: %v" via the configured logger)
//        }
//
// Supported Query Types:
//
//        Core Clauses:
//        - MATCH: Pattern matching and traversal
//        - OPTIONAL MATCH: Left outer joins (returns nulls for no matches)
//        - CREATE: Node and relationship creation
//        - MERGE: Upsert operations with ON CREATE SET / ON MATCH SET
//        - DELETE / DETACH DELETE: Node and relationship deletion
//        - SET: Property updates
//        - REMOVE: Property and label removal
//
//        Projection & Chaining:
//        - RETURN: Result projection with expressions, aliases, aggregations
//        - WITH: Query chaining and intermediate aggregation
//        - UNWIND: List expansion into rows
//
//        Filtering & Ordering:
//        - WHERE: Filtering conditions (=, <>, <, >, <=, >=, IS NULL, IS NOT NULL, IN, CONTAINS, STARTS WITH, ENDS WITH, AND, OR, NOT)
//        - ORDER BY: Result sorting (ASC/DESC)
//        - SKIP / LIMIT: Pagination
//
//        Aggregation Functions:
//        - COUNT, SUM, AVG, MIN, MAX, COLLECT
//
//        Procedures & Functions:
//        - CALL: Procedure invocation (db.labels, db.propertyKeys, db.index.vector.*, etc.)
//        - CALL {}: Subquery execution with UNION support
//
//        Advanced:
//        - UNION / UNION ALL: Query composition
//        - FOREACH: Iterative updates
//        - LOAD CSV: Data import
//        - EXPLAIN / PROFILE: Query analysis
//        - SHOW: Schema introspection
//
//        Path Functions:
//        - shortestPath / allShortestPaths
//
// Error Handling:
//
//        Returns detailed error messages for syntax errors, type mismatches,
//        and execution failures with Neo4j-compatible error codes.
func (e *StorageExecutor) Execute(ctx context.Context, cypher string, params map[string]interface{}) (result *ExecuteResult, retErr error) {
        e.resetHotPathTrace()
        defer func() {
                if retErr == nil && result != nil {
                        e.recordMaterializedResultAccess(result)
                }
        }()

        // TRC-15: top-level cypher execute span. Started before timing so the
        // span duration matches the metric observation window exactly. The span
        // is ended in the same defer that emits the slow-query log.
        ctx, execSpan := startExecuteSpan(ctx, "", cypher)

        // TRC-17: propagate span context to the storage layer so storage spans
        // nest as children of the cypher execute span.
        if te, ok := e.storage.(*storage.TracedEngine); ok {
                te.SetContext(ctx)
        }

        // D-04c slow-query log timing. Captured at the top so the threshold check
        // covers every Execute return path (early-out, fabric, normal). Pre-bind
        // the original query text — by the time the deferred emission fires,
        // `cypher` has been normalized; we want to log what the client submitted.
        slowStart := time.Now()
        originalCypher := cypher
        defer func() {
                dur := time.Since(slowStart)
                // Plan is unavailable for non-EXPLAIN/PROFILE queries; pass nil and
                // rely on PlanHash's zero-placeholder behavior. Phase 6 (TRC-04) will
                // thread the planned tree here once cypher EXPLAIN refactoring is in.
                e.emitSlowQueryLog(originalCypher, nil, dur)
                // Plan 04-03 / MET-08 slow_queries_total: increments only when
                // duration meets the configured threshold (matches the D-04c
                // emitSlowQueryLog gate semantics — single threshold, single
                // emission point per Execute return).
                e.observeSlowQueryIfThresholded(dur)
                recordSpanError(execSpan, retErr)
                execSpan.End()
        }()
        // Normalize query: trim BOM (some clients send it) then whitespace
        cypher = trimBOM(cypher)
        cypher = normalizeCypherSyntaxConfusables(cypher)
        cypher = strings.TrimSpace(cypher)
        cypher = trimTrailingStatementDelimiters(cypher)
        if cypher == "" {
                return nil, fmt.Errorf("empty query")
        }

        // Handle Neo4j shell/browser commands like :USE and :param before validation.
        processedQuery, processedCtx, shellResult, err := e.preprocessShellCommands(ctx, cypher, params)
        if err != nil {
                return nil, err
        }
        ctx = processedCtx
        cypher = processedQuery
        if cypher == "" {
                return shellResult, nil
        }

        // Route multi-graph CALL { USE ... } queries through the Fabric planner/executor
        // so subquery decomposition and cross-graph routing use a single deterministic path.
        if e.shouldUseFabricPlanner(cypher) {
                mergedParams := e.mergeShellParams(params)
                ctx = context.WithValue(ctx, paramsKey, mergedParams)
                info := e.analyzer.Analyze(cypher)
                // Plan 04-03 Site 3 (fabric branch): isFabric=true → op_type="fabric"
                // per RISK-1 corrected classifier. Observation pre-execute so the
                // counter reflects intent regardless of execution outcome (errors
                // still bucket by intended op_type, matching how queries_total works
                // in Phase 3 reference catalogs).
                e.observeQuery(classifyOpType(info, true /* isFabric */, false), true, slowStart)
                execSpan.SetAttributes(attribute.String("cypher.op_type", "fabric"))
                inExplicitTx := e.txContext != nil && e.txContext.active
                preparedFabric, err := e.prepareFabricExecution(ctx, cypher)
                if err != nil {
                        return nil, err
                }
                ctx = context.WithValue(ctx, fabricPreparedExecKey{}, preparedFabric)
                allowResultCache := !preparedFabric.hasRemote

                // Mirror normal query-cache policy for Fabric reads (autocommit only).
                if allowResultCache && !inExplicitTx && info.IsReadOnly && e.cache != nil && isCacheableReadQuery(cypher) {
                        if cached, found := e.cache.Get(cypher, mergedParams); found {
                                return cached, nil
                        }
                }

                var result *ExecuteResult
                var execErr error
                // When an explicit transaction is active on a composite route, execute through
                // the same FabricTransaction so many-read/one-write constraints are enforced
                // across all statements in the session.
                if inExplicitTx {
                        if ftx, ok := e.txContext.tx.(*fabric.FabricTransaction); ok {
                                result, execErr = e.executeViaPreparedFabricWithTx(ctx, cypher, mergedParams, ftx, false, preparedFabric)
                        } else {
                                result, execErr = e.executeViaFabric(ctx, cypher, mergedParams)
                        }
                } else {
                        result, execErr = e.executeViaFabric(ctx, cypher, mergedParams)
                }
                if execErr != nil {
                        return nil, execErr
                }

                if allowResultCache && !inExplicitTx && info.IsReadOnly && e.cache != nil && isCacheableReadQuery(cypher) {
                        ttl := 60 * time.Second
                        if info.HasAggregation {
                                ttl = 1 * time.Second
                        }
                        if info.HasCall || info.HasShow {
                                ttl = 300 * time.Second
                        }
                        e.cache.Put(cypher, mergedParams, result, ttl)
                }

                if info.IsWriteQuery && e.cache != nil {
                        if len(info.Labels) > 0 {
                                e.cache.InvalidateLabels(info.Labels)
                        } else {
                                e.cache.Invalidate()
                        }
                }

                return result, nil
        }

        // Handle leading Cypher USE clause (openCypher multi-graph syntax).
        if useDB, remaining, hasUse, err := parseLeadingUseClause(cypher); hasUse || err != nil {
                if err != nil {
                        return nil, err
                }
                scopedExec, resolvedDB, err := e.scopedExecutorForUse(useDB, GetAuthTokenFromContext(ctx))
                if err != nil {
                        return nil, err
                }
                ctx = context.WithValue(ctx, ctxKeyUseDatabase, resolvedDB)
                if strings.TrimSpace(remaining) == "" {
                        return &ExecuteResult{
                                Columns: []string{"database"},
                                Rows:    [][]interface{}{{resolvedDB}},
                        }, nil
                }
                return scopedExec.Execute(ctx, remaining, params)
        }

        // Reject data queries on composite root — callers must USE a constituent.
        // System/admin commands (SHOW DATABASES, CREATE/DROP DATABASE, ALTER, SHOW COMPOSITE,
        // SHOW CONSTITUENTS, SHOW ALIASES, SHOW LIMITS, BEGIN, COMMIT, ROLLBACK) are allowed.
        if isCompositeRoot(e.storage) && !isCompositeAllowedCommand(cypher) {
                return nil, fmt.Errorf("Neo.ClientError.Statement.NotAllowed: " +
                        "Queries on composite databases require explicit graph targeting. " +
                        "Use USE <composite>.<alias> to target a specific constituent")
        }

        // Merge session-scoped shell parameters with per-call parameters.
        // Explicit params win over shell params to preserve HTTP/Bolt semantics.
        params = e.mergeShellParams(params)

        // Check for transaction control statements and transaction scripts FIRST.
        // These are Nornic extensions and must bypass strict ANTLR validation.
        if result, err := e.executeTransactionScript(ctx, cypher); result != nil || err != nil {
                return result, err
        }
        if result, err := e.parseTransactionStatement(cypher); result != nil || err != nil {
                return result, err
        }

        // Validate basic syntax
        if err := e.validateSyntax(cypher); err != nil {
                // Plan 04-03 Site 2 (parse-error chokepoint): emit op_type="parse_error"
                // per D-04b sixth enum value. No duration observation — parse cost is
                // sub-microsecond and not meaningful to bucket. The queries_total
                // counter still increments so the SRE can alert on parse-error rate.
                e.observeQuery("parse_error", false /* observeDuration */, slowStart)
                execSpan.SetAttributes(attribute.String("cypher.op_type", "parse_error"))
                return nil, err
        }

        // IMPORTANT: Do NOT substitute parameters before routing!
        // We need to route the query based on the ORIGINAL query structure,
        // not the substituted one. Otherwise, keywords inside parameter values
        // (like 'MATCH (n) SET n.x = 1' stored as content) will be incorrectly
        // detected as Cypher clauses.
        //
        // Parameter substitution happens AFTER routing, inside each handler.
        // This matches Neo4j's architecture where params are kept separate.

        // Store params in context for handlers to use
        ctx = context.WithValue(ctx, paramsKey, params)

        // Check query limits if storage engine supports it
        // Uses interface{} to avoid importing multidb package (prevents circular dependencies)
        var queryLimitCancel context.CancelFunc
        if namespacedEngine, ok := e.storage.(interface {
                GetQueryLimitChecker() interface {
                        CheckQueryRate() error
                        CheckQueryLimits(context.Context) (context.Context, context.CancelFunc, error)
                }
        }); ok {
                if qlc := namespacedEngine.GetQueryLimitChecker(); qlc != nil {
                        // Check query rate limit
                        if err := qlc.CheckQueryRate(); err != nil {
                                return nil, err
                        }

                        // Check write rate limit for write queries
                        // We need to check this early, but we don't know if it's a write query yet
                        // So we'll check it in the write handlers too

                        // Apply query timeout and concurrent query limits
                        var err error
                        ctx, queryLimitCancel, err = qlc.CheckQueryLimits(ctx)
                        if err != nil {
                                return nil, err
                        }
                        // Ensure cancel is called when done
                        defer func() {
                                if queryLimitCancel != nil {
                                        queryLimitCancel()
                                }
                        }()
                }
        }

        // TRC-15: plan span wraps the analysis/classification phase.
        _, planSpan := startPlanSpan(ctx)
        // Analyze query - uses cached analysis if available
        // This extracts query metadata (HasMatch, IsReadOnly, Labels, etc.) once
        // and caches it for repeated queries, avoiding redundant string parsing
        info := e.analyzer.Analyze(cypher)

        // Plan 04-03 Sites 1 + 3 (RISK-1 corrected): classify ONCE post-Analyze.
        // isFabric=false here because the fabric branch returns at line ~963
        // before reaching this code path. isAdmin=true overrides the QueryInfo-
        // derived classification (e.g., SHOW DATABASES would otherwise classify
        // as "schema" via HasShow → IsSchemaQuery; D-04a says system/admin
        // commands bucket as "admin" instead). Single observation point covers
        // cache-hit early-return AND every downstream execution path so the
        // counter reflects intent regardless of how the query resolves.
        opType := classifyOpType(info, false /* isFabric */, isSystemCommandNoGraph(cypher))
        e.observeQuery(opType, true /* observeDuration */, slowStart)
        planSpan.SetAttributes(attribute.String("cypher.op_type", opType))
        planSpan.End()
        // Update the execute span with the resolved op_type.
        execSpan.SetAttributes(attribute.String("cypher.op_type", opType))

        // For routing, we still need upperQuery for some handlers
        // TODO: Migrate handlers to use QueryInfo directly
        upperQuery := e.cachedUpperQuery(cypher)

        // Try cache for read-only queries only when cache policy allows it.
        if info.IsReadOnly && e.cache != nil && isCacheableReadQuery(cypher) {
                if cached, found := e.cache.Get(cypher, params); found {
                        return cached, nil
                }
        }

        // Check for EXPLAIN/PROFILE execution modes (using cached analysis)
        if info.HasExplain {
                _, innerQuery := parseExecutionMode(cypher)
                return e.executeExplain(ctx, innerQuery)
        }
        if info.HasProfile {
                _, innerQuery := parseExecutionMode(cypher)
                return e.executeProfile(ctx, innerQuery)
        }

        // If in explicit transaction, execute within it
        if e.txContext != nil && e.txContext.active {
                return e.executeInTransaction(ctx, cypher, upperQuery)
        }

        // System commands (CREATE/DROP DATABASE, SHOW DATABASES, etc.) must not use the async engine
        // or implicit transactions: they operate on dbManager/metadata, not graph storage.
        // Routing them through executeWithoutTransaction directly ensures correct handling and
        // avoids the write path (tryAsyncCreateNodeBatch / executeWithImplicitTransaction).
        if isSystemCommandNoGraph(cypher) {
                result, err := e.executeWithoutTransaction(ctx, cypher, upperQuery)
                if err != nil {
                        return nil, err
                }
                return result, nil
        }

        // Auto-commit single query - use async path for performance
        // This uses AsyncEngine's write-behind cache instead of synchronous disk I/O
        // For strict ACID, users should use explicit BEGIN/COMMIT transactions
        result, err = e.executeImplicitAsync(ctx, cypher, upperQuery)

        // Apply result limit if set
        if err == nil && result != nil {
                if namespacedEngine, ok := e.storage.(interface {
                        GetQueryLimitChecker() interface {
                                GetQueryLimits() interface{}
                        }
                }); ok {
                        if qlc := namespacedEngine.GetQueryLimitChecker(); qlc != nil {
                                if queryLimits := qlc.GetQueryLimits(); queryLimits != nil {
                                        // Type assert to check if it has MaxResults field
                                        // We use reflection-like approach: check if it's a struct with MaxResults
                                        if limits, ok := queryLimits.(interface {
                                                GetMaxResults() int64
                                        }); ok {
                                                if maxResults := limits.GetMaxResults(); maxResults > 0 && int64(len(result.Rows)) > maxResults {
                                                        // Truncate results to limit
                                                        result.Rows = result.Rows[:maxResults]
                                                }
                                        }
                                }
                        }
                }
        }

        // Cache successful read-only queries.
        //
        // NOTE: Aggregation queries (COUNT/SUM/AVG/COLLECT/...) used to be excluded, but in practice they can still
        // be expensive (edge scans, label scans, COLLECT materialization). Caching them is correctness-preserving as
        // long as we invalidate on writes (which we do), so we cache them with a shorter TTL by default.
        if err == nil && info.IsReadOnly && e.cache != nil && isCacheableReadQuery(cypher) {
                // Determine TTL based on query type (using cached analysis)
                ttl := 60 * time.Second // Default: 60s for data queries
                if info.HasAggregation {
                        ttl = 1 * time.Second // Conservative TTL for aggregations
                }
                if info.HasCall || info.HasShow {
                        ttl = 300 * time.Second // 5 minutes for schema queries
                }
                e.cache.Put(cypher, params, result, ttl)
        }

        // Invalidate caches on write operations (using cached analysis)
        if info.IsWriteQuery {
                // Only invalidate node lookup cache when NODES are deleted
                // Relationship-only deletes (like benchmark CREATE rel DELETE rel) don't affect node cache
                if info.HasDelete && queryDeletesNodes(cypher) {
                        e.invalidateNodeLookupCache()
                }

                // Invalidate query result cache using cached labels
                if e.cache != nil {
                        if len(info.Labels) > 0 {
                                e.cache.InvalidateLabels(info.Labels)
                        } else {
                                e.cache.Invalidate()
                        }
                }
        }

        return result, err
}

// trimTrailingStatementDelimiters removes trailing Cypher statement delimiters
// (';') and surrounding whitespace, while leaving internal semicolons untouched.
// This mirrors Neo4j-compatible client behavior where a final semicolon is optional.
func trimTrailingStatementDelimiters(query string) string {
        s := strings.TrimSpace(query)
        for {
                if !strings.HasSuffix(s, ";") {
                        return s
                }
                s = strings.TrimSpace(strings.TrimSuffix(s, ";"))
        }
}

func normalizeCypherSyntaxConfusables(query string) string {
        if query == "" {
                return query
        }
        // Fast path: common ASCII-only Cypher text has no confusables to normalize.
        if isLikelyPlainASCIICypher(query) {
                return query
        }

        const (
                normalizeDefault = iota
                normalizeSingleQuoted
                normalizeDoubleQuoted
                normalizeBacktickQuoted
                normalizeLineComment
                normalizeBlockComment
        )

        runes := []rune(query)
        var builder strings.Builder
        builder.Grow(len(query) + 8)
        changed := false
        state := normalizeDefault

        for i := 0; i < len(runes); i++ {
                r := runes[i]
                next := rune(0)
                if i+1 < len(runes) {
                        next = runes[i+1]
                }

                switch state {
                case normalizeDefault:
                        switch {
                        case r == '/' && next == '/':
                                builder.WriteRune(r)
                                builder.WriteRune(next)
                                i++
                                state = normalizeLineComment
                                continue
                        case r == '/' && next == '*':
                                builder.WriteRune(r)
                                builder.WriteRune(next)
                                i++
                                state = normalizeBlockComment
                                continue
                        case r == '\'':
                                builder.WriteRune(r)
                                state = normalizeSingleQuoted
                                continue
                        case r == '"':
                                builder.WriteRune(r)
                                state = normalizeDoubleQuoted
                                continue
                        case r == '`':
                                builder.WriteRune(r)
                                state = normalizeBacktickQuoted
                                continue
                        }

                        if replacement, ok := cypherSyntaxConfusableReplacement(r); ok {
                                builder.WriteString(replacement)
                                changed = changed || replacement != string(r)
                                continue
                        }

                        if replacement, ok := cypherWhitespaceReplacement(r); ok {
                                builder.WriteRune(replacement)
                                changed = changed || replacement != r
                                continue
                        }

                        if isIgnorableCypherFormatRune(r) {
                                changed = true
                                continue
                        }

                        builder.WriteRune(r)

                case normalizeSingleQuoted:
                        builder.WriteRune(r)
                        if r == '\\' && i+1 < len(runes) {
                                builder.WriteRune(runes[i+1])
                                i++
                                continue
                        }
                        if r == '\'' {
                                if i+1 < len(runes) && runes[i+1] == '\'' {
                                        builder.WriteRune(runes[i+1])
                                        i++
                                        continue
                                }
                                state = normalizeDefault
                        }

                case normalizeDoubleQuoted:
                        builder.WriteRune(r)
                        if r == '\\' && i+1 < len(runes) {
                                builder.WriteRune(runes[i+1])
                                i++
                                continue
                        }
                        if r == '"' {
                                if i+1 < len(runes) && runes[i+1] == '"' {
                                        builder.WriteRune(runes[i+1])
                                        i++
                                        continue
                                }
                                state = normalizeDefault
                        }

                case normalizeBacktickQuoted:
                        builder.WriteRune(r)
                        if r == '`' {
                                if i+1 < len(runes) && runes[i+1] == '`' {
                                        builder.WriteRune(runes[i+1])
                                        i++
                                        continue
                                }
                                state = normalizeDefault
                        }

                case normalizeLineComment:
                        builder.WriteRune(r)
                        if r == '\n' || r == '\r' {
                                state = normalizeDefault
                        }

                case normalizeBlockComment:
                        builder.WriteRune(r)
                        if r == '*' && next == '/' {
                                builder.WriteRune(next)
                                i++
                                state = normalizeDefault
                        }
                }
        }

        if !changed {
                return query
        }

        return builder.String()
}

func isLikelyPlainASCIICypher(query string) bool {
        for i := 0; i < len(query); i++ {
                if query[i] >= 0x80 {
                        return false
                }
        }
        return true
}

// ensureUpperQueryCache lazily installs the upper-query cache pointer with
// sync.Once so concurrent CALL { ... } subqueries cannot race on the
// pointer assignment. The cache itself is mutex-guarded for entry access.
func (e *StorageExecutor) ensureUpperQueryCache() *upperQueryCache {
        e.upperQueryCacheOnce.Do(func() {
                if e.upperQueryCache == nil {
                        e.upperQueryCache = &upperQueryCache{
                                cache: make(map[string]string, 1024),
                                max:   4096,
                        }
                }
        })
        return e.upperQueryCache
}

func (e *StorageExecutor) cachedUpperQuery(query string) string {
        trimmed := strings.TrimSpace(query)
        if trimmed == "" {
                return ""
        }
        c := e.ensureUpperQueryCache()
        c.mu.RLock()
        if upper, ok := c.cache[trimmed]; ok {
                c.mu.RUnlock()
                return upper
        }
        c.mu.RUnlock()

        upper := strings.ToUpper(trimmed)
        c.mu.Lock()
        if len(c.cache) >= c.max {
                for k := range c.cache {
                        delete(c.cache, k)
                        break
                }
        }
        c.cache[trimmed] = upper
        c.mu.Unlock()
        return upper
}

func cypherSyntaxConfusableReplacement(r rune) (string, bool) {
        switch r {
        case '→':
                return "->", true
        case '←':
                return "<-", true
        case '—', '–', '−', '‐', '‑', '‒':
                return "-", true
        case '（':
                return "(", true
        case '）':
                return ")", true
        case '［':
                return "[", true
        case '］':
                return "]", true
        case '｛':
                return "{", true
        case '｝':
                return "}", true
        case '，':
                return ",", true
        case '：':
                return ":", true
        case '；':
                return ";", true
        case '．':
                return ".", true
        case '＝':
                return "=", true
        case '＜':
                return "<", true
        case '＞':
                return ">", true
        case '＄':
                return "$", true
        default:
                return "", false
        }
}

func cypherWhitespaceReplacement(r rune) (rune, bool) {
        switch r {
        case '\u0085', '\u2028', '\u2029':
                return '\n', true
        case ' ', '\t', '\n', '\r':
                return 0, false
        default:
                if unicode.IsSpace(r) {
                        return ' ', true
                }
                return 0, false
        }
}

func isIgnorableCypherFormatRune(r rune) bool {
        switch r {
        case '\u200B', '\u200C', '\u200D', '\u2060', '\uFEFF':
                return true
        default:
                return false
        }
}

// TransactionCapableEngine is an engine that supports ACID transactions.
// Used for type assertion to wrap implicit writes in rollback-capable transactions.
type TransactionCapableEngine interface {
        BeginTransaction() (*storage.BadgerTransaction, error)
}

type implicitTxEngines struct {
        txEngine    TransactionCapableEngine
        asyncEngine *storage.AsyncEngine
        namespace   string
}

func (e *StorageExecutor) resolveImplicitTxEngines() implicitTxEngines {
        engine := e.storage
        visited := make(map[storage.Engine]bool)
        out := implicitTxEngines{}

        for engine != nil && !visited[engine] {
                visited[engine] = true

                if out.namespace == "" {
                        if ns, ok := engine.(interface{ Namespace() string }); ok {
                                out.namespace = ns.Namespace()
                        }
                }
                if out.asyncEngine == nil {
                        if ae, ok := engine.(*storage.AsyncEngine); ok {
                                out.asyncEngine = ae
                        }
                }
                if out.txEngine == nil {
                        if tc, ok := engine.(TransactionCapableEngine); ok {
                                out.txEngine = tc
                        }
                }

                switch wrapper := engine.(type) {
                case interface{ GetUnderlying() storage.Engine }:
                        engine = wrapper.GetUnderlying()
                case interface{ GetEngine() storage.Engine }:
                        engine = wrapper.GetEngine()
                case interface{ GetInnerEngine() storage.Engine }:
                        engine = wrapper.GetInnerEngine()
                default:
                        engine = nil
                }
        }

        return out
}

func (e *StorageExecutor) tryAsyncCreateNodeBatch(ctx context.Context, cypher string) (*ExecuteResult, error, bool) {
        upper := strings.ToUpper(strings.TrimSpace(cypher))
        if !strings.HasPrefix(upper, "CREATE") {
                return nil, nil, false
        }
        // System commands and schema commands must not be handled here — route to executeSchemaCommand instead
        if findMultiWordKeywordIndex(cypher, "CREATE", "DATABASE") == 0 ||
                findMultiWordKeywordIndex(cypher, "CREATE", "COMPOSITE DATABASE") == 0 ||
                findMultiWordKeywordIndex(cypher, "CREATE", "ALIAS") == 0 ||
                findMultiWordKeywordIndex(cypher, "CREATE", "CONSTRAINT") == 0 ||
                findMultiWordKeywordIndex(cypher, "CREATE", "INDEX") == 0 ||
                findMultiWordKeywordIndex(cypher, "CREATE", "FULLTEXT") == 0 ||
                findMultiWordKeywordIndex(cypher, "CREATE", "VECTOR") == 0 ||
                findMultiWordKeywordIndex(cypher, "CREATE", "RANGE") == 0 {
                return nil, nil, false
        }
        for _, keyword := range []string{
                "MATCH",
                "MERGE",
                "SET",
                "DELETE",
                "DETACH",
                "REMOVE",
                "WITH",
                "CALL",
                "UNWIND",
                "FOREACH",
                "LOAD",
                "OPTIONAL",
        } {
                if containsKeywordOutsideStrings(cypher, keyword) {
                        return nil, nil, false
                }
        }

        // Substitute parameters before parsing so (n:Label $props) becomes (n:Label { ... })
        // and the label is not mis-parsed as "Label $props".
        if params := getParamsFromContext(ctx); params != nil {
                cypher = e.substituteParams(cypher, params)
        }

        returnIdx := findKeywordIndex(cypher, "RETURN")
        createPart := cypher
        if returnIdx > 0 {
                createPart = strings.TrimSpace(cypher[:returnIdx])
        }

        createClauses := SplitByCreate(createPart)
        if len(createClauses) == 0 {
                return nil, nil, false
        }

        var nodePatterns []string
        for _, clause := range createClauses {
                clause = strings.TrimSpace(clause)
                if clause == "" {
                        continue
                }
                patterns := e.splitCreatePatterns(clause)
                for _, pat := range patterns {
                        pat = strings.TrimSpace(pat)
                        if pat == "" {
                                continue
                        }
                        if containsOutsideStrings(pat, "->") ||
                                containsOutsideStrings(pat, "<-") ||
                                containsOutsideStrings(pat, "]-") ||
                                containsOutsideStrings(pat, "-[") {
                                return nil, nil, false
                        }
                        nodePatterns = append(nodePatterns, pat)
                }
        }

        if len(nodePatterns) == 0 {
                return nil, nil, false
        }

        result := &ExecuteResult{
                Columns: []string{},
                Rows:    [][]interface{}{},
                Stats:   &QueryStats{},
        }

        createdNodes := make(map[string]*storage.Node)
        nodes := make([]*storage.Node, 0, len(nodePatterns))
        for _, nodePatternStr := range nodePatterns {
                nodePattern := e.parseNodePattern(ctx, nodePatternStr)

                for _, label := range nodePattern.labels {
                        if !isValidIdentifier(label) {
                                return nil, fmt.Errorf("invalid label name: %q (must be alphanumeric starting with letter or underscore)", label), true
                        }
                        if containsReservedKeyword(label) {
                                return nil, fmt.Errorf("invalid label name: %q (contains reserved keyword)", label), true
                        }
                }

                for key, val := range nodePattern.properties {
                        if !isValidIdentifier(key) {
                                return nil, fmt.Errorf("invalid property key: %q (must be alphanumeric starting with letter or underscore)", key), true
                        }
                        if _, ok := val.(invalidPropertyValue); ok {
                                return nil, fmt.Errorf("invalid property value for key %q: malformed syntax", key), true
                        }
                }

                node := &storage.Node{
                        ID:         storage.NodeID(e.generateID()),
                        Labels:     nodePattern.labels,
                        Properties: nodePattern.properties,
                }
                nodes = append(nodes, node)
                if nodePattern.variable != "" {
                        createdNodes[nodePattern.variable] = node
                }
        }

        store := e.getStorage(ctx)
        if err := store.BulkCreateNodes(nodes); err != nil {
                return nil, err, true
        }

        for _, node := range nodes {
                e.notifyNodeMutated(string(node.ID))
                addOptimisticNodeID(result, node.ID)
        }
        result.Stats.NodesCreated += len(nodes)

        if returnIdx > 0 {
                returnPart := strings.TrimSpace(cypher[returnIdx+6:])
                returnItems := e.parseReturnItems(returnPart)

                result.Columns = make([]string, len(returnItems))
                row := make([]interface{}, len(returnItems))
                for i, item := range returnItems {
                        if item.alias != "" {
                                result.Columns[i] = item.alias
                        } else {
                                result.Columns[i] = item.expr
                        }

                        for variable, node := range createdNodes {
                                if strings.HasPrefix(item.expr, variable) || item.expr == variable {
                                        row[i] = e.resolveReturnItem(ctx, item, variable, node)
                                        break
                                }
                        }

                        if row[i] == nil {
                                if varName := extractVariableNameFromReturnItem(item.expr); varName != "" {
                                        if node, ok := createdNodes[varName]; ok {
                                                row[i] = e.resolveReturnItem(ctx, item, varName, node)
                                        }
                                }
                        }
                }
                result.Rows = [][]interface{}{row}
        }

        return result, nil, true
}

func (e *StorageExecutor) isEventualAsyncEligible(info *QueryInfo, cypher string) bool {
        if info == nil || !info.IsWriteQuery {
                return false
        }
        if info.HasSchema || info.IsSchemaQuery || isSystemCommandNoGraph(cypher) || isCreateProcedureCommand(cypher) {
                return false
        }
        if info.FirstClause != ClauseCreate || !info.HasCreate {
                return false
        }
        if info.HasMatch || info.HasOptionalMatch || info.HasMerge || info.HasDelete || info.HasDetachDelete ||
                info.HasSet || info.HasRemove || info.HasWith || info.HasUnwind || info.HasCall ||
                info.HasForeach || info.HasLoadCSV || info.HasUnion {
                return false
        }
        return true
}

// executeImplicitAsync executes a single query using implicit transactions for writes.
// For write operations, wraps execution in an implicit transaction that can be
// rolled back on error, preventing partial data corruption from failed queries.
// For strict ACID guarantees with durability, use explicit BEGIN/COMMIT transactions.
func (e *StorageExecutor) executeImplicitAsync(ctx context.Context, cypher string, upperQuery string) (*ExecuteResult, error) {
        // Check if this is a write operation using cached analysis
        info := e.analyzer.Analyze(cypher)
        isWrite := info.IsWriteQuery

        // For write operations, use implicit transaction for atomicity
        // This ensures partial writes are rolled back on error
        if isWrite {
                if hasCallInTransactions(cypher) {
                        return e.executeWithoutTransaction(ctx, cypher, upperQuery)
                }
                engines := e.resolveImplicitTxEngines()
                if engines.asyncEngine != nil {
                        if result, err, handled := e.tryAsyncCreateNodeBatch(ctx, cypher); handled {
                                return result, err
                        }
                        if e.isEventualAsyncEligible(info, cypher) {
                                return e.executeWithoutTransaction(ctx, cypher, upperQuery)
                        }
                }
                return e.executeWithImplicitTransaction(ctx, cypher, upperQuery)
        }

        // Read-only operations don't need transaction wrapping
        return e.executeWithoutTransaction(ctx, cypher, upperQuery)
}

// executeWithImplicitTransaction wraps a write query in a single implicit
// transaction. Commit-time conflicts are returned to the caller; retry-aware
// clients own any replay decision because NornicDB does not know whether a
// conflict is recoverable for the application.
func (e *StorageExecutor) executeWithImplicitTransaction(ctx context.Context, cypher string, upperQuery string) (*ExecuteResult, error) {
        parsedCypher, inlineEmbeddingEnabled := stripWithEmbeddingSuffix(cypher)
        if inlineEmbeddingEnabled {
                cypher = parsedCypher
                upperQuery = strings.ToUpper(cypher)
        }

        // Try to get a transaction-capable engine and async wrapper (if present)
        engines := e.resolveImplicitTxEngines()
        if engines.namespace == "" {
                if dbName := strings.TrimSpace(GetUseDatabaseFromContext(ctx)); dbName != "" {
                        engines.namespace = dbName
                } else if _, dbName := e.resolveWALAndDatabase(); strings.TrimSpace(dbName) != "" {
                        engines.namespace = strings.TrimSpace(dbName)
                }
        }
        txEngine := engines.txEngine
        asyncEngine := engines.asyncEngine

        // If no transaction support, fall back to direct execution (legacy mode)
        // This is less safe but maintains backward compatibility
        if txEngine == nil {
                if inlineEmbeddingEnabled {
                        return nil, fmt.Errorf("WITH EMBEDDING requires transaction-capable storage")
                }
                result, err := e.executeWithoutTransaction(ctx, cypher, upperQuery)
                if err != nil {
                        return nil, err
                }
                // Flush if needed
                if !e.deferFlush {
                        if asyncEngine != nil {
                                asyncEngine.Flush()
                        }
                }
                return result, nil
        }

        // IMPORTANT: If using AsyncEngine with pending writes, flush its cache BEFORE
        // starting the transaction. This ensures the BadgerTransaction can see all
        // previously written data. Without this, MATCH queries in compound statements
        // (MATCH...CREATE) would fail to find nodes in AsyncEngine's cache.
        // We use HasPendingWrites() first as a cheap check to avoid unnecessary flushes.
        if asyncEngine != nil && asyncEngine.HasPendingWrites() {
                asyncEngine.Flush()
        }
        releaseAsyncFlushHold := func() {}
        if asyncEngine != nil {
                release := asyncEngine.HoldFlush()
                held := true
                releaseAsyncFlushHold = func() {
                        if held {
                                release()
                                held = false
                        }
                }
                defer releaseAsyncFlushHold()
        }

        // Start implicit transaction
        if engines.namespace != "" {
                if primer, ok := txEngine.(interface{ EnsureNamespaceMVCC(string) error }); ok {
                        if err := primer.EnsureNamespaceMVCC(engines.namespace); err != nil {
                                return nil, fmt.Errorf("failed to prime implicit transaction namespace: %w", err)
                        }
                }
        }
        tx, err := txEngine.BeginTransaction()
        if err != nil {
                return nil, fmt.Errorf("failed to start implicit transaction: %w", err)
        }
        if engines.namespace != "" {
                if err := tx.SetNamespace(engines.namespace); err != nil {
                        _ = tx.Rollback()
                        return nil, fmt.Errorf("failed to pin implicit transaction namespace: %w", err)
                }
        }

        // Defer constraint validation to commit for implicit transactions.
        // This avoids duplicate per-operation checks and improves write throughput.
        if err := tx.SetDeferredConstraintValidation(true); err != nil {
                _ = tx.Rollback()
                return nil, fmt.Errorf("failed to configure implicit transaction: %w", err)
        }
        if err := tx.SetSkipCreateExistenceCheck(true); err != nil {
                _ = tx.Rollback()
                return nil, fmt.Errorf("failed to configure implicit transaction: %w", err)
        }
        // Skip the per-commit engine.Sync(). The Bolt session's end-of-session
        // Flush and the async engine's ticker-driven flush coalesce durability
        // for implicit writes; forcing an Msync per UNWIND batch turned every
        // batch into a 300µs syscall for no user-visible benefit.
        if err := tx.SetImplicit(true); err != nil {
                _ = tx.Rollback()
                return nil, fmt.Errorf("failed to configure implicit transaction: %w", err)
        }

        // Optional WAL transaction markers for receipts.
        var wal *storage.WAL
        var walSeqStart uint64
        txID := tx.ID
        var dbName string
        if txID != "" {
                wal, dbName = e.resolveWALAndDatabase()
                if wal != nil {
                        walSeqStart, err = wal.AppendTxBegin(dbName, txID, nil)
                        if err != nil {
                                _ = tx.Rollback()
                                return nil, fmt.Errorf("failed to write WAL tx begin: %w", err)
                        }
                }
        }

        // Create a transactional wrapper that routes writes through the transaction
        // CRITICAL: We pass the wrapper through context instead of modifying e.storage
        // because e.storage modification is NOT thread-safe for concurrent executions.
        separator := ":"
        if engines.namespace == "" {
                separator = ""
        }
        txWrapper := &transactionStorageWrapper{
                tx:             tx,
                underlying:     e.storage,
                namespace:      engines.namespace,
                separator:      separator,
                mutatedNodeIDs: make(map[string]struct{}),
        }

        // Execute with transaction wrapper via context
        txCtx := context.WithValue(ctx, ctxKeyTxStorage, txWrapper)
        txExec := e.cloneWithStorage(txWrapper)

        // Execute the query
        result, execErr := txExec.executeWithoutTransaction(txCtx, cypher, upperQuery)

        // Handle result
        if execErr != nil {
                // Rollback on any error - prevents partial data corruption
                tx.Rollback()
                txExec.invalidateNodeLookupCache()
                if wal != nil && walSeqStart > 0 {
                        _, _ = wal.AppendTxAbort(dbName, txID, execErr.Error())
                }
                return nil, execErr
        }

        if inlineEmbeddingEnabled {
                if err := txExec.applyInlineEmbeddingMutations(txCtx, txWrapper.snapshotMutatedNodeIDs()); err != nil {
                        tx.Rollback()
                        txExec.invalidateNodeLookupCache()
                        if wal != nil && walSeqStart > 0 {
                                _, _ = wal.AppendTxAbort(dbName, txID, err.Error())
                        }
                        return nil, err
                }
        }

        // Commit successful transaction
        if err := tx.Commit(); err != nil {
                txExec.invalidateNodeLookupCache()
                if wal != nil && walSeqStart > 0 {
                        _, _ = wal.AppendTxAbort(dbName, txID, err.Error())
                }
                if info := e.analyzer.Analyze(cypher); IsRetrySafeMergeCommitQuery(info) {
                        err = nornicerrors.MarkMergeCommitTimeUniqueConflict(err)
                }
                // Wire contract: substring "commit failed" is matched by downstream Bolt classifiers.
                // See docs/plans/consumer-pinned-error-contract-plan.md §2.1.
                // The implicit-autocommit path was historically wrapped with "failed to commit
                // implicit transaction: ..." which broke the consumer-pinned classifier; aligned
                // with pkg/cypher/transaction.go:181 so the explicit and implicit paths produce the
                // same wire shape.
                return nil, fmt.Errorf("commit failed: %w", err)
        }

        // Attach receipt metadata if WAL markers were recorded.
        if wal != nil && walSeqStart > 0 {
                opCount := tx.OperationCount()
                if commitSeq, walErr := wal.AppendTxCommit(dbName, txID, opCount); walErr == nil {
                        if receipt, recErr := storage.NewReceipt(txID, walSeqStart, commitSeq, dbName, time.Now().UTC()); recErr == nil {
                                if result.Metadata == nil {
                                        result.Metadata = make(map[string]interface{})
                                }
                                result.Metadata["receipt"] = receipt
                        }
                }
        }

        // Promote the tx-scoped MERGE lookup cache into the parent so
        // subsequent Execute calls still benefit from the cross-query
        // speedup. Tx isolation is preserved because each in-flight tx had
        // its own clone; only post-commit entries graduate to the parent.
        txExec.promoteNodeLookupCacheTo(e)

        // Flush if needed for durability
        if !e.deferFlush && asyncEngine != nil {
                releaseAsyncFlushHold()
                asyncEngine.Flush()
        }

        return result, nil
}

// ctxKeyTxStorage is the context key for transaction storage wrapper.
type ctxKeyTxStorageType struct{}

var ctxKeyTxStorage = ctxKeyTxStorageType{}

func (e *StorageExecutor) applyInlineEmbeddingMutations(ctx context.Context, ids map[string]struct{}) error {
        if len(ids) == 0 {
                return nil
        }
        if e.embedder == nil {
                return fmt.Errorf("WITH EMBEDDING requires configured embedder")
        }
        store := e.getStorage(ctx)
        for id := range ids {
                node, err := store.GetNode(storage.NodeID(id))
                if err != nil {
                        if err == storage.ErrNotFound {
                                continue
                        }
                        return err
                }
                if node == nil {
                        continue
                }
                text := embeddingutil.BuildText(node.Properties, node.Labels, e.inlineEmbeddingTextOptions)
                chunks, err := e.embedder.ChunkText(text, e.inlineEmbeddingChunkSize, e.inlineEmbeddingChunkOverlap)
                if err != nil {
                        return fmt.Errorf("WITH EMBEDDING chunking failed for node %s: %w", id, err)
                }
                if len(chunks) == 0 {
                        chunks = []string{text}
                }
                embeddings := make([][]float32, 0, len(chunks))
                for _, chunk := range chunks {
                        emb, err := e.embedder.Embed(ctx, chunk)
                        if err != nil {
                                return fmt.Errorf("WITH EMBEDDING embed failed for node %s: %w", id, err)
                        }
                        if len(emb) == 0 {
                                return fmt.Errorf("WITH EMBEDDING embed returned empty vector for node %s", id)
                        }
                        embeddings = append(embeddings, emb)
                }
                model := "inline-cypher"
                dimensions := len(embeddings[0])
                if named, ok := e.embedder.(interface{ Model() string }); ok {
                        if v := strings.TrimSpace(named.Model()); v != "" {
                                model = v
                        }
                }
                if d, ok := e.embedder.(interface{ Dimensions() int }); ok {
                        if v := d.Dimensions(); v > 0 {
                                dimensions = v
                        }
                }
                embeddingutil.ApplyManagedEmbedding(node, embeddings, model, dimensions, time.Now())
                if err := store.UpdateNode(node); err != nil {
                        return err
                }
        }
        return nil
}

func stripWithEmbeddingSuffix(cypher string) (string, bool) {
        idx := findKeywordIndex(cypher, "WITH EMBEDDING")
        if idx < 0 {
                return cypher, false
        }
        before := strings.TrimSpace(cypher[:idx])
        after := strings.TrimSpace(cypher[idx+len("WITH EMBEDDING"):])
        if before == "" {
                return cypher, false
        }
        if after == "" {
                return before, true
        }
        return strings.TrimSpace(before + " " + after), true
}

func maxInt(a, b int) int {
        if a > b {
                return a
        }
        return b
}

// ctxKeyUseDatabase is the context key for :USE database switching.
// When :USE database_name is detected, the database name is stored in context
// so the server can switch to that database before executing the query.
type ctxKeyUseDatabaseType struct{}

var ctxKeyUseDatabase = ctxKeyUseDatabaseType{}

// ctxKeyAuthToken carries an Authorization header value for remote/OIDC forwarding.
type ctxKeyAuthTokenType struct{}

var ctxKeyAuthToken = ctxKeyAuthTokenType{}

// GetUseDatabaseFromContext extracts the database name from :USE command if present in context.
// Returns empty string if no :USE command was found.
func GetUseDatabaseFromContext(ctx context.Context) string {
        if dbName, ok := ctx.Value(ctxKeyUseDatabase).(string); ok {
                return dbName
        }
        return ""
}

// WithAuthToken stores an Authorization header token on context for execution paths
// that need to forward caller identity across remote constituents.
func WithAuthToken(ctx context.Context, authToken string) context.Context {
        if strings.TrimSpace(authToken) == "" {
                return ctx
        }
        return context.WithValue(ctx, ctxKeyAuthToken, authToken)
}

// GetAuthTokenFromContext extracts forwarded Authorization token from context.
func GetAuthTokenFromContext(ctx context.Context) string {
        if v, ok := ctx.Value(ctxKeyAuthToken).(string); ok {
                return v
        }
        return ""
}

// getStorage returns the storage to use for the current execution.
// If a transaction wrapper is present in context, it uses that; otherwise uses e.storage.
func (e *StorageExecutor) getStorage(ctx context.Context) storage.Engine {
        if txWrapper, ok := ctx.Value(ctxKeyTxStorage).(*transactionStorageWrapper); ok {
                return txWrapper
        }
        return e.storage
}

// resolveWALAndDatabase attempts to find a WAL instance and database name
// by unwrapping common storage wrappers (namespaced, async, WAL engines).
func (e *StorageExecutor) resolveWALAndDatabase() (*storage.WAL, string) {
        engine := e.storage
        var dbName string

        for engine != nil {
                if ns, ok := engine.(interface{ Namespace() string }); ok && dbName == "" {
                        dbName = ns.Namespace()
                }
                if walProvider, ok := engine.(interface{ GetWAL() *storage.WAL }); ok {
                        return walProvider.GetWAL(), dbName
                }
                switch wrapper := engine.(type) {
                case interface{ GetUnderlying() storage.Engine }:
                        engine = wrapper.GetUnderlying()
                case interface{ GetEngine() storage.Engine }:
                        engine = wrapper.GetEngine()
                case interface{ GetInnerEngine() storage.Engine }:
                        engine = wrapper.GetInnerEngine()
                default:
                        return nil, dbName
                }
        }

        return nil, dbName
}

// transactionStorageWrapper wraps a BadgerTransaction to implement storage.Engine
// for use in implicit transaction execution. It routes writes through the transaction
// (for atomicity/rollback) and reads through the underlying engine (for performance).
type transactionStorageWrapper struct {
        tx               *storage.BadgerTransaction
        underlying       storage.Engine // For read operations not supported by transaction
        namespace        string
        separator        string
        mutatedNodeIDs   map[string]struct{}
        mutatedNodeIDsMu sync.Mutex

        // txNodeLookupCache scopes the executor's MERGE/MATCH lookup cache to
        // this single transaction. Concurrent transactions get distinct
        // wrappers — and therefore distinct caches — so a peer's uncommitted
        // node-ID mapping cannot leak into this transaction's read set via
        // store.GetNode(...) inside tx.badgerTx (which would otherwise put
        // the peer's node key into Badger's SSI read set and convert a
        // constraint violation into a generic Transaction Conflict). Within
        // a single transaction the cache is shared across re-entries that
        // reuse the same wrapper, so multi-clause queries still benefit
        // from the cross-clause speedup.
        txNodeLookupCache   map[string]*storage.Node
        txNodeLookupCacheMu *sync.RWMutex
}

func (w *transactionStorageWrapper) Namespace() string {
        if w == nil {
                return ""
        }
        return w.namespace
}

// ensureNodeLookupCacheLocked lazily initializes the wrapper's MERGE/MATCH
// lookup cache, seeding it once from the parent executor's committed
// entries. The cache exists for the lifetime of the transaction; on
// commit, executor code drains it back into the parent executor via
// promoteNodeLookupCacheTo, on rollback the wrapper is discarded and the
// cache with it. Subsequent calls (e.g. recursive Execute re-entry on
// the same wrapper) are no-ops, so the in-tx state survives across
// multi-clause queries.
func (w *transactionStorageWrapper) ensureNodeLookupCacheLocked(seedFrom *StorageExecutor) {
        if w.txNodeLookupCacheMu != nil && w.txNodeLookupCache != nil {
                return
        }
        w.txNodeLookupCacheMu = &sync.RWMutex{}
        w.txNodeLookupCache = make(map[string]*storage.Node, 1000)
        if seedFrom == nil {
                return
        }
        srcMu := seedFrom.nodeLookupCacheLock()
        srcMu.RLock()
        for k, v := range seedFrom.nodeLookupCache {
                w.txNodeLookupCache[k] = v
        }
        srcMu.RUnlock()
}

func (w *transactionStorageWrapper) GetEngine() storage.Engine {
        if w == nil {
                return nil
        }
        return w.underlying
}

func (w *transactionStorageWrapper) markMutatedNodeID(id storage.NodeID) {
        if id == "" || w.mutatedNodeIDs == nil {
                return
        }
        w.mutatedNodeIDsMu.Lock()
        w.mutatedNodeIDs[string(id)] = struct{}{}
        w.mutatedNodeIDsMu.Unlock()
}

func (w *transactionStorageWrapper) snapshotMutatedNodeIDs() map[string]struct{} {
        if len(w.mutatedNodeIDs) == 0 {
                return nil
        }
        w.mutatedNodeIDsMu.Lock()
        defer w.mutatedNodeIDsMu.Unlock()
        out := make(map[string]struct{}, len(w.mutatedNodeIDs))
        for id := range w.mutatedNodeIDs {
                out[id] = struct{}{}
        }
        return out
}

// Write operations - go through transaction for atomicity
func (w *transactionStorageWrapper) CreateNode(node *storage.Node) (storage.NodeID, error) {
        if w.namespace == "" {
                id, err := w.tx.CreateNode(node)
                if err == nil {
                        w.markMutatedNodeID(id)
                }
                return id, err
        }
        namespaced := storage.CopyNode(node)
        namespaced.ID = w.prefixNodeID(node.ID)
        actualID, err := w.tx.CreateNode(namespaced)
        if err != nil {
                return "", err
        }
        userID := w.unprefixNodeID(actualID)
        w.markMutatedNodeID(userID)
        return userID, nil
}

func (w *transactionStorageWrapper) UpdateNode(node *storage.Node) error {
        if w.namespace == "" {
                err := w.tx.UpdateNode(node)
                if err == nil {
                        w.markMutatedNodeID(node.ID)
                }
                return err
        }
        namespaced := storage.CopyNode(node)
        namespaced.ID = w.prefixNodeID(node.ID)
        err := w.tx.UpdateNode(namespaced)
        if err == nil {
                w.markMutatedNodeID(node.ID)
        }
        return err
}

func (w *transactionStorageWrapper) DeleteNode(id storage.NodeID) error {
        return w.tx.DeleteNode(w.prefixNodeID(id))
}

func (w *transactionStorageWrapper) CreateEdge(edge *storage.Edge) error {
        if w.namespace == "" {
                return w.tx.CreateEdge(edge)
        }
        namespaced := storage.CopyEdge(edge)
        namespaced.ID = w.prefixEdgeID(edge.ID)
        namespaced.StartNode = w.prefixNodeID(edge.StartNode)
        namespaced.EndNode = w.prefixNodeID(edge.EndNode)
        return w.tx.CreateEdge(namespaced)
}

func (w *transactionStorageWrapper) DeleteEdge(id storage.EdgeID) error {
        return w.tx.DeleteEdge(w.prefixEdgeID(id))
}

// Read operations - transaction supports GetNode, forward others to underlying
func (w *transactionStorageWrapper) GetNode(id storage.NodeID) (*storage.Node, error) {
        node, err := w.tx.GetNode(w.prefixNodeID(id))
        if err != nil {
                return nil, err
        }
        if w.namespace == "" {
                return node, nil
        }
        return w.toUserNode(node), nil
}

func (w *transactionStorageWrapper) GetEdge(id storage.EdgeID) (*storage.Edge, error) {
        if w.namespace == "" {
                return w.tx.GetEdge(id)
        }
        edge, err := w.tx.GetEdge(w.prefixEdgeID(id))
        if err != nil {
                return nil, err
        }
        return w.toUserEdge(edge), nil
}

func (w *transactionStorageWrapper) UpdateEdge(edge *storage.Edge) error {
        if w.namespace == "" {
                return w.tx.UpdateEdge(edge)
        }
        namespaced := storage.CopyEdge(edge)
        namespaced.ID = w.prefixEdgeID(edge.ID)
        namespaced.StartNode = w.prefixNodeID(edge.StartNode)
        namespaced.EndNode = w.prefixNodeID(edge.EndNode)
        return w.tx.UpdateEdge(namespaced)
}

func (w *transactionStorageWrapper) GetNodesByLabel(label string) ([]*storage.Node, error) {
        nodes, err := w.tx.GetNodesByLabel(label)
        if err != nil {
                return nil, err
        }
        if w.namespace == "" {
                return nodes, nil
        }
        return w.toUserNodes(nodes), nil
}

func (w *transactionStorageWrapper) GetFirstNodeByLabel(label string) (*storage.Node, error) {
        node, err := w.tx.GetFirstNodeByLabel(label)
        if err != nil {
                return nil, err
        }
        if w.namespace == "" {
                return node, nil
        }
        return w.toUserNode(node), nil
}

func (w *transactionStorageWrapper) ForEachNodeIDByLabel(label string, visit func(storage.NodeID) bool) error {
        if visit == nil {
                return nil
        }
        if !w.tx.HasPendingNodeMutations() {
                if lookup, ok := w.underlying.(storage.LabelNodeIDLookupEngine); ok {
                        return lookup.ForEachNodeIDByLabel(label, visit)
                }
        }

        nodes, err := w.GetNodesByLabel(label)
        if err != nil {
                return err
        }
        for _, node := range nodes {
                if node == nil {
                        continue
                }
                if !visit(node.ID) {
                        return nil
                }
        }
        return nil
}

func (w *transactionStorageWrapper) GetOutgoingEdges(nodeID storage.NodeID) ([]*storage.Edge, error) {
        if w.namespace == "" {
                return w.tx.GetOutgoingEdges(nodeID)
        }
        edges, err := w.tx.GetOutgoingEdges(w.prefixNodeID(nodeID))
        if err != nil {
                return nil, err
        }
        return w.toUserEdges(edges), nil
}

func (w *transactionStorageWrapper) GetIncomingEdges(nodeID storage.NodeID) ([]*storage.Edge, error) {
        if w.namespace == "" {
                return w.tx.GetIncomingEdges(nodeID)
        }
        edges, err := w.tx.GetIncomingEdges(w.prefixNodeID(nodeID))
        if err != nil {
                return nil, err
        }
        return w.toUserEdges(edges), nil
}

func (w *transactionStorageWrapper) GetEdgesBetween(startID, endID storage.NodeID) ([]*storage.Edge, error) {
        if w.namespace == "" {
                return w.tx.GetEdgesBetween(startID, endID)
        }
        edges, err := w.tx.GetEdgesBetween(w.prefixNodeID(startID), w.prefixNodeID(endID))
        if err != nil {
                return nil, err
        }
        return w.toUserEdges(edges), nil
}

func (w *transactionStorageWrapper) GetEdgeBetween(startID, endID storage.NodeID, edgeType string) *storage.Edge {
        if w.namespace == "" {
                return w.tx.GetEdgeBetween(startID, endID, edgeType)
        }
        edge := w.tx.GetEdgeBetween(w.prefixNodeID(startID), w.prefixNodeID(endID), edgeType)
        if edge == nil {
                return nil
        }
        return w.toUserEdge(edge)
}

func (w *transactionStorageWrapper) GetEdgesByType(edgeType string) ([]*storage.Edge, error) {
        if w.namespace == "" {
                return w.tx.GetEdgesByType(edgeType)
        }
        edges, err := w.tx.GetEdgesByType(edgeType)
        if err != nil {
                return nil, err
        }
        return w.toUserEdges(edges), nil
}

func (w *transactionStorageWrapper) GetNodesByLabelVisibleAt(label string, version storage.MVCCVersion) ([]*storage.Node, error) {
        if provider, ok := w.underlying.(storage.MVCCIndexedVisibilityEngine); ok {
                return provider.GetNodesByLabelVisibleAt(label, version)
        }
        return nil, storage.ErrNotImplemented
}

func (w *transactionStorageWrapper) GetOutgoingEdgesVisibleAt(nodeID storage.NodeID, version storage.MVCCVersion) ([]*storage.Edge, error) {
        provider, ok := w.underlying.(storage.MVCCIndexedVisibilityEngine)
        if !ok {
                return nil, storage.ErrNotImplemented
        }
        edges, err := provider.GetOutgoingEdgesVisibleAt(w.prefixNodeID(nodeID), version)
        if err != nil || w.namespace == "" {
                return edges, err
        }
        return w.toUserEdges(edges), nil
}

func (w *transactionStorageWrapper) GetIncomingEdgesVisibleAt(nodeID storage.NodeID, version storage.MVCCVersion) ([]*storage.Edge, error) {
        provider, ok := w.underlying.(storage.MVCCIndexedVisibilityEngine)
        if !ok {
                return nil, storage.ErrNotImplemented
        }
        edges, err := provider.GetIncomingEdgesVisibleAt(w.prefixNodeID(nodeID), version)
        if err != nil || w.namespace == "" {
                return edges, err
        }
        return w.toUserEdges(edges), nil
}

func (w *transactionStorageWrapper) GetEdgesByTypeVisibleAt(edgeType string, version storage.MVCCVersion) ([]*storage.Edge, error) {
        if provider, ok := w.underlying.(storage.MVCCIndexedVisibilityEngine); ok {
                return provider.GetEdgesByTypeVisibleAt(edgeType, version)
        }
        return nil, storage.ErrNotImplemented
}

func (w *transactionStorageWrapper) GetEdgesBetweenVisibleAt(startID, endID storage.NodeID, version storage.MVCCVersion) ([]*storage.Edge, error) {
        if provider, ok := w.underlying.(storage.MVCCIndexedVisibilityEngine); ok {
                return provider.GetEdgesBetweenVisibleAt(startID, endID, version)
        }
        return nil, storage.ErrNotImplemented
}

func (w *transactionStorageWrapper) AllNodes() ([]*storage.Node, error) {
        nodes, err := w.tx.AllNodes()
        if err != nil {
                return nil, err
        }
        if w.namespace == "" {
                return nodes, nil
        }
        return w.toUserNodes(nodes), nil
}

func (w *transactionStorageWrapper) AllEdges() ([]*storage.Edge, error) {
        return w.underlying.AllEdges()
}

func (w *transactionStorageWrapper) GetAllNodes() []*storage.Node {
        nodes := w.tx.GetAllNodes()
        if w.namespace == "" {
                return nodes
        }
        return w.toUserNodes(nodes)
}

func (w *transactionStorageWrapper) GetInDegree(nodeID storage.NodeID) int {
        return w.underlying.GetInDegree(nodeID)
}

func (w *transactionStorageWrapper) GetOutDegree(nodeID storage.NodeID) int {
        return w.underlying.GetOutDegree(nodeID)
}

func (w *transactionStorageWrapper) GetSchema() *storage.SchemaManager {
        return w.underlying.GetSchema()
}

func (w *transactionStorageWrapper) BulkCreateNodes(nodes []*storage.Node) error {
        // For bulk operations within transaction, create one by one
        for _, node := range nodes {
                if w.namespace == "" {
                        if _, err := w.tx.CreateNode(node); err != nil {
                                return err
                        }
                        continue
                }
                namespaced := storage.CopyNode(node)
                namespaced.ID = w.prefixNodeID(node.ID)
                if _, err := w.tx.CreateNode(namespaced); err != nil {
                        return err
                }
        }
        return nil
}

func (w *transactionStorageWrapper) BulkCreateEdges(edges []*storage.Edge) error {
        if len(edges) == 0 {
                return nil
        }
        if w.namespace == "" {
                return w.tx.BulkCreateEdges(edges)
        }
        namespaced := make([]*storage.Edge, len(edges))
        for i, edge := range edges {
                cp := storage.CopyEdge(edge)
                cp.ID = w.prefixEdgeID(edge.ID)
                cp.StartNode = w.prefixNodeID(edge.StartNode)
                cp.EndNode = w.prefixNodeID(edge.EndNode)
                namespaced[i] = cp
        }
        return w.tx.BulkCreateEdges(namespaced)
}

func (w *transactionStorageWrapper) BulkDeleteNodes(ids []storage.NodeID) error {
        for _, id := range ids {
                if err := w.tx.DeleteNode(w.prefixNodeID(id)); err != nil {
                        return err
                }
        }
        return nil
}

func (w *transactionStorageWrapper) BulkDeleteEdges(ids []storage.EdgeID) error {
        for _, id := range ids {
                if err := w.tx.DeleteEdge(w.prefixEdgeID(id)); err != nil {
                        return err
                }
        }
        return nil
}

func (w *transactionStorageWrapper) prefixNodeID(id storage.NodeID) storage.NodeID {
        if w.namespace == "" {
                return id
        }
        prefix := w.namespace + w.separator
        if strings.HasPrefix(string(id), prefix) {
                return id
        }
        return storage.NodeID(w.namespace + w.separator + string(id))
}

func (w *transactionStorageWrapper) unprefixNodeID(id storage.NodeID) storage.NodeID {
        if w.namespace == "" {
                return id
        }
        prefix := w.namespace + w.separator
        s := string(id)
        if strings.HasPrefix(s, prefix) {
                return storage.NodeID(s[len(prefix):])
        }
        return id
}

func (w *transactionStorageWrapper) prefixEdgeID(id storage.EdgeID) storage.EdgeID {
        if w.namespace == "" {
                return id
        }
        prefix := w.namespace + w.separator
        if strings.HasPrefix(string(id), prefix) {
                return id
        }
        return storage.EdgeID(w.namespace + w.separator + string(id))
}

func (w *transactionStorageWrapper) unprefixEdgeID(id storage.EdgeID) storage.EdgeID {
        if w.namespace == "" {
                return id
        }
        prefix := w.namespace + w.separator
        s := string(id)
        if strings.HasPrefix(s, prefix) {
                return storage.EdgeID(s[len(prefix):])
        }
        return id
}

func (w *transactionStorageWrapper) toUserNode(node *storage.Node) *storage.Node {
        if node == nil {
                return nil
        }
        out := storage.CopyNode(node)
        out.ID = w.unprefixNodeID(out.ID)
        return out
}

func (w *transactionStorageWrapper) toUserEdge(edge *storage.Edge) *storage.Edge {
        if edge == nil {
                return nil
        }
        out := storage.CopyEdge(edge)
        out.ID = w.unprefixEdgeID(out.ID)
        out.StartNode = w.unprefixNodeID(out.StartNode)
        out.EndNode = w.unprefixNodeID(out.EndNode)
        return out
}

func (w *transactionStorageWrapper) toUserEdges(edges []*storage.Edge) []*storage.Edge {
        out := make([]*storage.Edge, 0, len(edges))
        for _, edge := range edges {
                out = append(out, w.toUserEdge(edge))
        }
        return out
}

func (w *transactionStorageWrapper) toUserNodes(nodes []*storage.Node) []*storage.Node {
        out := make([]*storage.Node, 0, len(nodes))
        for _, node := range nodes {
                out = append(out, w.toUserNode(node))
        }
        return out
}

func (w *transactionStorageWrapper) BatchGetNodes(ids []storage.NodeID) (map[storage.NodeID]*storage.Node, error) {
        return w.underlying.BatchGetNodes(ids)
}

func (w *transactionStorageWrapper) Close() error {
        // Don't close underlying engine
        return nil
}

func (w *transactionStorageWrapper) NodeCount() (int64, error) {
        return w.underlying.NodeCount()
}

func (w *transactionStorageWrapper) EdgeCount() (int64, error) {
        return w.underlying.EdgeCount()
}

func (w *transactionStorageWrapper) DeleteByPrefix(prefix string) (nodesDeleted int64, edgesDeleted int64, err error) {
        // DeleteByPrefix is not supported within a transaction context.
        // This operation should be performed outside of a transaction.
        return 0, 0, fmt.Errorf("DeleteByPrefix not supported within transaction context")
}

// tryFastPathCompoundQuery attempts to handle common compound query patterns
// using structured scanning rather than regex capture arrays.
// Returns (result, true) if handled, (nil, false) if the query should go through normal routing.
//
// Pattern: MATCH (a:Label), (b:Label) WITH a, b LIMIT 1 CREATE (a)-[r:Type]->(b) DELETE r
// This is a very common pattern in benchmarks and relationship tests.
func (e *StorageExecutor) tryFastPathCompoundQuery(ctx context.Context, cypher string) (*ExecuteResult, bool) {
        if match, ok := matchCompoundQueryShape(cypher); ok {
                switch match.Kind {
                case shapeKindCompoundCreateDeleteRel:
                        e.markCompoundQueryFastPathUsed()
                        return e.executeFastPathCreateDeleteRel(
                                match.Captures.String("label1"),
                                match.Captures.String("label2"),
                                match.Captures.String("prop1"),
                                match.Captures.Any("value1"),
                                match.Captures.String("prop2"),
                                match.Captures.Any("value2"),
                                match.Captures.String("rel_type"),
                        )
                case shapeKindCompoundPropCreateDeleteRel:
                        e.markCompoundQueryFastPathUsed()
                        return e.executeFastPathCreateDeleteRel(
                                match.Captures.String("label1"),
                                match.Captures.String("label2"),
                                match.Captures.String("prop1"),
                                match.Captures.Any("value1"),
                                match.Captures.String("prop2"),
                                match.Captures.Any("value2"),
                                match.Captures.String("rel_type"),
                        )
                case shapeKindCompoundPropCreateDeleteReturnCountRel:
                        e.markCompoundQueryFastPathUsed()
                        return e.executeFastPathCreateDeleteRelCount(
                                match.Captures.String("label1"),
                                match.Captures.String("label2"),
                                match.Captures.String("prop1"),
                                match.Captures.Any("value1"),
                                match.Captures.String("prop2"),
                                match.Captures.Any("value2"),
                                match.Captures.String("rel_type"),
                                match.Captures.String("rel_var"),
                        )
                }
        }

        return nil, false
}

// executeFastPathCreateDeleteRel executes the fast-path for MATCH...CREATE...DELETE patterns.
// If prop1/prop2 are empty, uses GetFirstNodeByLabel. Otherwise uses property lookup.
func (e *StorageExecutor) executeFastPathCreateDeleteRel(label1, label2, prop1 string, val1 any, prop2 string, val2 any, relType string) (*ExecuteResult, bool) {
        var err error

        // Get node1
        if prop1 == "" {
                _, err = storage.FirstNodeIDByLabel(e.storage, label1)
        } else {
                node1 := e.findNodeByLabelAndProperty(label1, prop1, val1)
                if node1 == nil {
                        return nil, false
                }
        }
        if err != nil {
                return nil, false
        }

        // Get node2
        if prop2 == "" {
                _, err = storage.FirstNodeIDByLabel(e.storage, label2)
        } else {
                node2 := e.findNodeByLabelAndProperty(label2, prop2, val2)
                if node2 == nil {
                        return nil, false
                }
        }
        if err != nil {
                return nil, false
        }

        // Optimization: This pattern creates a relationship and deletes it in the same
        // statement without returning it. The relationship is not observable to the user,
        // and the net graph effect is a no-op, so we skip storage writes entirely.
        //
        // We still validate that both endpoints exist (via the lookups above) and we
        // still return correct query stats for Neo4j compatibility.

        return &ExecuteResult{
                Columns: []string{},
                Rows:    [][]interface{}{},
                Stats: &QueryStats{
                        RelationshipsCreated: 1,
                        RelationshipsDeleted: 1,
                },
        }, true
}

func (e *StorageExecutor) executeFastPathCreateDeleteRelCount(label1, label2, prop1 string, val1 any, prop2 string, val2 any, relType string, relVar string) (*ExecuteResult, bool) {
        var err error

        if prop1 == "" {
                _, err = storage.FirstNodeIDByLabel(e.storage, label1)
        } else {
                node1 := e.findNodeByLabelAndProperty(label1, prop1, val1)
                if node1 == nil {
                        return nil, false
                }
        }
        if err != nil {
                return nil, false
        }

        if prop2 == "" {
                _, err = storage.FirstNodeIDByLabel(e.storage, label2)
        } else {
                node2 := e.findNodeByLabelAndProperty(label2, prop2, val2)
                if node2 == nil {
                        return nil, false
                }
        }
        if err != nil {
                return nil, false
        }

        return &ExecuteResult{
                Columns: []string{"count(" + relVar + ")"},
                Rows:    [][]interface{}{{int64(1)}},
                Stats: &QueryStats{
                        RelationshipsCreated: 1,
                        RelationshipsDeleted: 1,
                },
        }, true
}

// findNodeByLabelAndProperty finds a node by label and a single property value.
// Uses the node lookup cache for O(1) repeated lookups.
func (e *StorageExecutor) findNodeByLabelAndProperty(label, prop string, val any) *storage.Node {
        e.ensureNodeLookupCache()

        // Try cache first (with proper locking)
        cacheKey := fmt.Sprintf("%s:{%s:%v}", label, prop, val)
        cacheMu := e.nodeLookupCacheLock()
        cacheMu.RLock()
        if cached, ok := e.nodeLookupCache[cacheKey]; ok {
                cacheMu.RUnlock()
                return cached
        }
        cacheMu.RUnlock()

        // Scan nodes with label
        nodes, err := e.storage.GetNodesByLabel(label)
        if err != nil {
                return nil
        }

        // Find matching node
        for _, node := range nodes {
                if nodeVal, ok := node.Properties[prop]; ok {
                        if fmt.Sprintf("%v", nodeVal) == fmt.Sprintf("%v", val) {
                                // Cache for next time (with proper locking)
                                cacheMu.Lock()
                                e.nodeLookupCache[cacheKey] = node
                                cacheMu.Unlock()
                                return node
                        }
                }
        }

        return nil
}

// isSystemCommandNoGraph returns true for statements that operate on database metadata
// (CREATE/DROP DATABASE, SHOW DATABASES, etc.) and must not use the async engine or
// implicit transactions. These are routed to executeWithoutTransaction directly.
func isSystemCommandNoGraph(cypher string) bool {
        return findMultiWordKeywordIndex(cypher, "CREATE", "COMPOSITE DATABASE") == 0 ||
                findMultiWordKeywordIndex(cypher, "CREATE", "DATABASE") == 0 ||
                findMultiWordKeywordIndex(cypher, "CREATE", "ALIAS") == 0 ||
                findMultiWordKeywordIndex(cypher, "DROP", "COMPOSITE DATABASE") == 0 ||
                findMultiWordKeywordIndex(cypher, "DROP", "DATABASE") == 0 ||
                findMultiWordKeywordIndex(cypher, "DROP", "ALIAS") == 0 ||
                findMultiWordKeywordIndex(cypher, "SHOW", "DATABASES") == 0 ||
                findMultiWordKeywordIndex(cypher, "ALTER", "DATABASE") == 0
}

func isShowConstraintContractsCommand(cypher string) bool {
        return findMultiWordKeywordIndex(cypher, "SHOW", "CONSTRAINT CONTRACTS") == 0
}

// executeWithoutTransaction executes query without transaction wrapping (original path).
func (e *StorageExecutor) executeWithoutTransaction(ctx context.Context, cypher string, upperQuery string) (*ExecuteResult, error) {
        // FAST PATH: Simple MATCH-return-limit reads should never be routed through
        // heavier compound planners. Keep this check first to avoid regressions when
        // adding complex routing rules.
        if result, handled := e.tryFastPathSimpleMatchReturnLimit(ctx, cypher, upperQuery); handled {
                return result, nil
        }
        if result, handled := e.tryFastPathAnyMatchVectorCosine(ctx, cypher, upperQuery); handled {
                return result, nil
        }

        // FAST PATH: Check for common compound query patterns using pre-compiled regex
        // This avoids multiple findKeywordIndex calls for frequently-used patterns
        if result, handled := e.tryFastPathCompoundQuery(ctx, cypher); handled {
                return result, nil
        }

        // Route to appropriate handler based on query type
        // upperQuery is passed in to avoid redundant conversion

        // Cache keyword checks to avoid repeated searches
        startsWithMatch := strings.HasPrefix(upperQuery, "MATCH")
        startsWithCreate := strings.HasPrefix(upperQuery, "CREATE")
        startsWithMerge := strings.HasPrefix(upperQuery, "MERGE")

        // Correlated MATCH ... CALL { ... } must route before generic MATCH...CREATE/MERGE
        // detection, because CREATE/MERGE/SET tokens can legally appear inside the
        // CALL subquery body and should not trigger outer compound handlers.
        if startsWithMatch && hasSubqueryPattern(cypher, callSubqueryRe) {
                return e.executeMatchWithCallSubquery(ctx, cypher)
        }

        // MATCH ... CALL procedure() must route before generic MATCH ... CREATE/MERGE
        // detection because procedure names such as db.create.setNodeVectorProperty
        // contain clause-looking tokens that are not outer query clauses.
        if startsWithMatch {
                callIdx := findKeywordIndex(cypher, "CALL")
                if callIdx > 0 {
                        callPart := strings.TrimSpace(cypher[callIdx:])
                        if !isCallSubquery(callPart) {
                                prefix := cypher[:callIdx]
                                hasMutationBeforeCall := findKeywordIndexInContext(prefix, "MERGE") >= 0 ||
                                        findKeywordIndexInContext(prefix, "CREATE") >= 0 ||
                                        findKeywordIndexInContext(prefix, "SET") >= 0 ||
                                        findKeywordIndexInContext(prefix, "DELETE") >= 0 ||
                                        findKeywordIndexInContext(prefix, "DETACH DELETE") >= 0 ||
                                        findKeywordIndexInContext(prefix, "REMOVE") >= 0
                                if hasMutationBeforeCall {
                                        goto skipMatchCallRoute
                                }
                                if findKeywordIndex(cypher[:callIdx], "WITH") > 0 {
                                        return e.executeMatchWithClause(ctx, cypher)
                                }
                                return e.executeMatchWithCallProcedure(ctx, cypher)
                        }
                }
        }
skipMatchCallRoute:

        // MERGE queries get special handling - they have their own ON CREATE SET / ON MATCH SET logic
        if startsWithMerge {
                // Complex MERGE pipelines that include OPTIONAL MATCH / WITH / WHERE should
                // use the segment executor instead of the single-MERGE parser.
                if findKeywordIndexInContext(cypher, "OPTIONAL MATCH") > 0 ||
                        findKeywordIndexInContext(cypher, "WITH") > 0 ||
                        findKeywordIndexInContext(cypher, "WHERE") > 0 {
                        return e.executeMultipleMerges(ctx, cypher)
                }
                // Check for multiple MERGEs without WITH (e.g., MERGE (a) MERGE (b) MERGE (a)-[:REL]->(b))
                firstMergeEnd := findKeywordIndex(cypher[5:], ")")
                if firstMergeEnd > 0 {
                        afterFirstMerge := cypher[5+firstMergeEnd+1:]
                        secondMergeIdx := findKeywordIndex(afterFirstMerge, "MERGE")
                        if secondMergeIdx >= 0 {
                                return e.executeMultipleMerges(ctx, cypher)
                        }
                }
                return e.executeMerge(ctx, cypher)
        }

        // Cache findKeywordIndex results for compound query detection
        var mergeIdx, createIdx, withIdx, deleteIdx, optionalMatchIdx int = -1, -1, -1, -1, -1

        if startsWithMatch {
                // Only search for keywords if query starts with MATCH
                mergeIdx = findKeywordIndex(cypher, "MERGE")
                createIdx = findKeywordIndex(cypher, "CREATE")
                optionalMatchIdx = findMultiWordKeywordIndex(cypher, "OPTIONAL", "MATCH")
        } else if startsWithCreate {
                // Check for multiple CREATE statements (e.g., CREATE (a) CREATE (b) CREATE (a)-[:REL]->(b))
                firstCreateEnd := findKeywordIndex(cypher[6:], ")")
                if firstCreateEnd > 0 {
                        afterFirstCreate := cypher[6+firstCreateEnd+1:]
                        secondCreateIdx := findKeywordIndex(afterFirstCreate, "CREATE")
                        if secondCreateIdx >= 0 {
                                return e.executeMultipleCreates(ctx, cypher)
                        }
                }
                // Only search for WITH/DELETE if query starts with CREATE
                withIdx = findKeywordIndex(cypher, "WITH")
                if withIdx > 0 {
                        deleteIdx = findKeywordIndex(cypher, "DELETE")
                }
        }

        // Compound queries: MATCH ... MERGE ... (with variable references)
        if startsWithMatch && mergeIdx > 0 {
                return e.executeCompoundMatchMerge(ctx, cypher)
        }

        // Compound queries: MATCH ... CREATE ... (create relationship between matched nodes)
        if startsWithMatch && createIdx > 0 {
                // Try the general pipeline executor first — it handles composite
                // queries like MATCH ... CREATE ... WITH ... UNWIND ... MATCH ...
                // CREATE ... which executeCompoundMatchCreate miscategorises
                // (treats everything after the first CREATE as CREATE patterns,
                // consuming intervening WITH/UNWIND/MATCH clauses as property map
                // garbage).
                if result, ok, err := e.executePipeline(ctx, cypher); ok {
                        return result, err
                }
                return e.executeCompoundMatchCreate(ctx, cypher)
        }

        // Compound queries: CREATE ... WITH ... DELETE (create then delete in same statement)
        if startsWithCreate && withIdx > 0 && deleteIdx > 0 {
                return e.executeCompoundCreateWithDelete(ctx, cypher)
        }

        // UNWIND pipelines may contain trailing DELETE/SET/REMOVE keywords.
        // Route UNWIND before generic mutation keyword checks so
        // `UNWIND ... MATCH ... REMOVE ...` does not get misrouted to executeRemove.
        if findKeywordIndex(cypher, "UNWIND") == 0 {
                return e.executeUnwind(ctx, cypher)
        }

        // Cache contains checks for DELETE - use word-boundary-aware detection
        // Note: Can't use " DELETE " because DELETE is often followed by variable name (DELETE n)
        // findKeywordIndex handles word boundaries properly (won't match 'ToDelete' in string literals)
        hasDelete := findKeywordIndex(cypher, "DELETE") > 0 // Must be after MATCH, not at start
        hasDetachDelete := containsKeywordOutsideStrings(cypher, "DETACH DELETE")

        // Check for compound queries - MATCH ... DELETE, MATCH ... SET, etc.
        if hasDelete || hasDetachDelete {
                return e.executeDelete(ctx, cypher)
        }

        // Cache SET-related checks - use string-literal-aware detection to avoid
        // matching keywords inside user content like 'MATCH (n) SET n.x = 1'
        // Note: findKeywordIndex already checks word boundaries, so no need for leading space
        hasSet := containsKeywordOutsideStrings(cypher, "SET")
        hasOnCreateSet := containsKeywordOutsideStrings(cypher, "ON CREATE SET")
        hasOnMatchSet := containsKeywordOutsideStrings(cypher, "ON MATCH SET")

        // NEO4J COMPAT: Handle CREATE ... SET pattern (e.g., CREATE (n) SET n.x = 1)
        // Neo4j allows SET immediately after CREATE without requiring MATCH
        if startsWithCreate && !isCreateProcedureCommand(cypher) && hasSet && !hasOnCreateSet && !hasOnMatchSet &&
                findMultiWordKeywordIndex(cypher, "CREATE", "DECAY PROFILE") != 0 &&
                findMultiWordKeywordIndex(cypher, "CREATE", "PROMOTION PROFILE") != 0 &&
                findMultiWordKeywordIndex(cypher, "CREATE", "PROMOTION POLICY") != 0 {
                return e.executeCreateSet(ctx, cypher)
        }

        // Check for ALTER DATABASE before generic SET (ALTER DATABASE SET LIMIT contains "SET")
        if findMultiWordKeywordIndex(cypher, "ALTER", "DATABASE") == 0 {
                return e.executeAlterDatabase(ctx, cypher)
        }

        // Only route to executeSet if it's a MATCH ... SET or standalone SET
        if hasSet && !isCreateProcedureCommand(cypher) && !hasOnCreateSet && !hasOnMatchSet &&
                findMultiWordKeywordIndex(cypher, "CREATE", "DECAY PROFILE") != 0 &&
                findMultiWordKeywordIndex(cypher, "CREATE", "PROMOTION PROFILE") != 0 &&
                findMultiWordKeywordIndex(cypher, "CREATE", "PROMOTION POLICY") != 0 &&
                findMultiWordKeywordIndex(cypher, "ALTER", "DECAY PROFILE") != 0 &&
                findMultiWordKeywordIndex(cypher, "ALTER", "PROMOTION PROFILE") != 0 &&
                findMultiWordKeywordIndex(cypher, "ALTER", "PROMOTION POLICY") != 0 {
                if startsWithMatch || findKeywordIndex(cypher, "SET") == 0 {
                        return e.executeSet(ctx, cypher)
                }
        }

        // Handle MATCH ... REMOVE (property removal) - string-literal-aware
        // Note: findKeywordIndex already checks word boundaries
        if containsKeywordOutsideStrings(cypher, "REMOVE") {
                return e.executeRemove(ctx, cypher)
        }

        // Compound queries: MATCH ... OPTIONAL MATCH ...
        // But NOT when there's a WITH clause before OPTIONAL MATCH (that's handled by executeMatchWithOptionalMatch)
        if startsWithMatch && optionalMatchIdx > 0 {
                // Check if there's a WITH clause BEFORE OPTIONAL MATCH
                // If so, route to the specialized handler that processes WITH first
                withBeforeOptional := findKeywordIndex(cypher[:optionalMatchIdx], "WITH")
                if withBeforeOptional > 0 {
                        // WITH comes before OPTIONAL MATCH - route to executeMatchWithOptionalMatch
                        return e.executeMatchWithOptionalMatch(ctx, cypher)
                }
                return e.executeCompoundMatchOptionalMatch(ctx, cypher)
        }

        switch {
        case isCreateProcedureCommand(cypher):
                return e.executeCreateProcedure(ctx, cypher)
        case findMultiWordKeywordIndex(cypher, "CREATE", "DECAY PROFILE") == 0,
                findMultiWordKeywordIndex(cypher, "CREATE", "PROMOTION PROFILE") == 0,
                findMultiWordKeywordIndex(cypher, "CREATE", "PROMOTION POLICY") == 0:
                return e.executeKnowledgePolicyDDL(ctx, cypher)
        case findMultiWordKeywordIndex(cypher, "OPTIONAL", "MATCH") == 0:
                // OPTIONAL MATCH must be at start (position 0) to be a standalone clause
                // Handles flexible whitespace: "OPTIONAL MATCH", "OPTIONAL\tMATCH", "OPTIONAL\nMATCH", etc.
                return e.executeOptionalMatch(ctx, cypher)
        case startsWithMatch && isShortestPathQuery(cypher):
                // Handle shortestPath() and allShortestPaths() queries.
                // Parameter substitution must happen before parsing so the variable-
                // binding lookup for `MATCH (start:Star {starId: $startId})` resolves
                // to the actual property value rather than the literal `$startId`.
                // Without this, `findNodeByPattern` matches no node, the executor
                // falls through to AllNodes() × AllNodes(), and the BFS explodes.
                spCypher := cypher
                if params := getParamsFromContext(ctx); params != nil {
                        spCypher = e.substituteParams(spCypher, params)
                }
                query, err := e.parseShortestPathQuery(ctx, spCypher)
                if err != nil {
                        return nil, err
                }
                return e.executeShortestPathQuery(ctx, query)
        case startsWithMatch:
                // Multi-MATCH chains have dedicated routing inside executeMatch (executeMultiMatch,
                // executeChainedMatchWithAggregations). Keep them on that path to preserve WHERE
                // semantics across MATCH boundaries.
                matchCount := countKeywordOccurrences(upperQuery, "MATCH")
                optionalMatchCount := countKeywordOccurrences(upperQuery, "OPTIONAL MATCH")
                isMultiMatch := matchCount-optionalMatchCount > 1
                if !isMultiMatch {
                        // Check for optimizable patterns FIRST
                        patternInfo := DetectQueryPattern(ctx, cypher)
                        if patternInfo.IsOptimizable() {
                                if result, ok := e.ExecuteOptimized(ctx, cypher, patternInfo); ok {
                                        return result, nil
                                }
                                // Fall through to generic on optimization failure
                        }
                }
                return e.executeMatch(ctx, cypher)
        case findMultiWordKeywordIndex(cypher, "CREATE", "CONSTRAINT") == 0,
                findMultiWordKeywordIndex(cypher, "CREATE", "RANGE INDEX") == 0,
                findMultiWordKeywordIndex(cypher, "CREATE", "FULLTEXT INDEX") == 0,
                findMultiWordKeywordIndex(cypher, "CREATE", "VECTOR INDEX") == 0,
                findKeywordIndex(cypher, "CREATE INDEX") == 0:
                // Schema commands - constraints and indexes (check more specific patterns first)
                // Must be at start (position 0) to be a standalone clause
                return e.executeSchemaCommand(ctx, cypher)
        case findMultiWordKeywordIndex(cypher, "CREATE", "COMPOSITE DATABASE") == 0:
                // System command: CREATE COMPOSITE DATABASE (check before CREATE DATABASE)
                // Must be at start (position 0) to be a standalone clause
                return e.executeCreateCompositeDatabase(ctx, cypher)
        case findMultiWordKeywordIndex(cypher, "CREATE", "DATABASE") == 0:
                // System command: CREATE DATABASE (check before generic CREATE)
                // Must be at start (position 0) to be a standalone clause
                // Handles flexible whitespace: "CREATE DATABASE", "CREATE\tDATABASE", "CREATE\nDATABASE", etc.
                return e.executeCreateDatabase(ctx, cypher)
        case findMultiWordKeywordIndex(cypher, "CREATE", "ALIAS") == 0:
                // System command: CREATE ALIAS (check before generic CREATE)
                // Must be at start (position 0) to be a standalone clause
                // Handles flexible whitespace: "CREATE ALIAS", "CREATE\tALIAS", "CREATE\nALIAS", etc.
                return e.executeCreateAlias(ctx, cypher)
        case startsWithCreate:
                return e.executeCreate(ctx, cypher)
        case hasDelete || hasDetachDelete:
                // DELETE/DETACH DELETE already detected above with findKeywordIndex
                return e.executeDelete(ctx, cypher)
        case findKeywordIndex(cypher, "CALL") == 0:
                // Distinguish CALL {} subquery from CALL procedure()
                // Must be at start (position 0) to be a standalone clause
                if isCallSubquery(cypher) {
                        return e.executeCallSubquery(ctx, cypher)
                }
                return e.executeCall(ctx, cypher)
        case findKeywordIndex(cypher, "RETURN") == 0:
                // Must be at start (position 0) to be a standalone clause
                return e.executeReturn(ctx, cypher)
        case findMultiWordKeywordIndex(cypher, "DROP", "COMPOSITE DATABASE") == 0:
                // System command: DROP COMPOSITE DATABASE (check before DROP DATABASE)
                // Must be at start (position 0) to be a standalone clause
                return e.executeDropCompositeDatabase(ctx, cypher)
        case findMultiWordKeywordIndex(cypher, "DROP", "DATABASE") == 0:
                // System command: DROP DATABASE (check before generic DROP)
                // Must be at start (position 0) to be a standalone clause
                // Handles flexible whitespace: "DROP DATABASE", "DROP\tDATABASE", "DROP\nDATABASE", etc.
                return e.executeDropDatabase(ctx, cypher)
        case findMultiWordKeywordIndex(cypher, "DROP", "ALIAS") == 0:
                // System command: DROP ALIAS (check before generic DROP)
                // Must be at start (position 0) to be a standalone clause
                // Handles flexible whitespace: "DROP ALIAS", "DROP\tALIAS", "DROP\nALIAS", etc.
                return e.executeDropAlias(ctx, cypher)
        case findMultiWordKeywordIndex(cypher, "DROP", "CONSTRAINT") == 0:
                // Schema command: DROP CONSTRAINT (must not be treated as generic DROP no-op).
                // Must be at start (position 0) to be a standalone clause.
                return e.executeSchemaCommand(ctx, cypher)
        case findMultiWordKeywordIndex(cypher, "DROP", "DECAY PROFILE") == 0,
                findMultiWordKeywordIndex(cypher, "DROP", "PROMOTION PROFILE") == 0,
                findMultiWordKeywordIndex(cypher, "DROP", "PROMOTION POLICY") == 0:
                return e.executeKnowledgePolicyDDL(ctx, cypher)
        case isDropProcedureCommand(cypher):
                return e.executeDropProcedure(ctx, cypher)
        case findMultiWordKeywordIndex(cypher, "DROP", "INDEX") == 0:
                // DROP INDEX — execute real drop against the target schema.
                return e.executeDropIndex(ctx, cypher)
        case findKeywordIndex(cypher, "DROP") == 0:
                // Other DROP variants (not INDEX, not CONSTRAINT, not ALIAS, not PROCEDURE)
                // treat as no-op for forward compatibility.
                return &ExecuteResult{Columns: []string{}, Rows: [][]interface{}{}}, nil
        case findKeywordIndex(cypher, "WITH") == 0:
                // Must be at start (position 0) to be a standalone clause
                return e.executeWith(ctx, cypher)
        case findKeywordIndex(cypher, "UNWIND") == 0:
                // Must be at start (position 0) to be a standalone clause
                return e.executeUnwind(ctx, cypher)
        case findKeywordIndex(cypher, "UNION ALL") >= 0:
                // UNION ALL can appear anywhere in query
                return e.executeUnion(ctx, cypher, true)
        case findKeywordIndex(cypher, "UNION") >= 0:
                // UNION can appear anywhere in query
                return e.executeUnion(ctx, cypher, false)
        case findKeywordIndex(cypher, "FOREACH") == 0:
                // Must be at start (position 0) to be a standalone clause
                return e.executeForeach(ctx, cypher)
        case findKeywordIndex(cypher, "LOAD CSV") == 0:
                // Must be at start (position 0) to be a standalone clause
                return e.executeLoadCSV(ctx, cypher)
        // SHOW commands for Neo4j compatibility
        case findMultiWordKeywordIndex(cypher, "SHOW", "FULLTEXT INDEXES") == 0,
                findMultiWordKeywordIndex(cypher, "SHOW", "FULLTEXT INDEX") == 0,
                findMultiWordKeywordIndex(cypher, "SHOW", "RANGE INDEXES") == 0,
                findMultiWordKeywordIndex(cypher, "SHOW", "RANGE INDEX") == 0,
                findMultiWordKeywordIndex(cypher, "SHOW", "VECTOR INDEXES") == 0,
                findMultiWordKeywordIndex(cypher, "SHOW", "VECTOR INDEX") == 0:
                // Must be at start (position 0) to be a standalone clause
                return e.executeShowIndexes(ctx, cypher)
        case findMultiWordKeywordIndex(cypher, "SHOW", "INDEXES") == 0,
                findMultiWordKeywordIndex(cypher, "SHOW", "INDEX") == 0:
                // Must be at start (position 0) to be a standalone clause
                return e.executeShowIndexes(ctx, cypher)
        case findMultiWordKeywordIndex(cypher, "SHOW", "DECAY PROFILES") == 0,
                findMultiWordKeywordIndex(cypher, "SHOW", "PROMOTION PROFILES") == 0,
                findMultiWordKeywordIndex(cypher, "SHOW", "PROMOTION POLICIES") == 0:
                return e.executeKnowledgePolicyDDL(ctx, cypher)
        case findMultiWordKeywordIndex(cypher, "SHOW", "CONSTRAINTS") == 0,
                findMultiWordKeywordIndex(cypher, "SHOW", "CONSTRAINT") == 0:
                // Must be at start (position 0) to be a standalone clause
                return e.executeShowConstraints(ctx, cypher)
        case findMultiWordKeywordIndex(cypher, "SHOW", "PROCEDURES") == 0:
                // Must be at start (position 0) to be a standalone clause
                return e.executeShowProcedures(ctx, cypher)
        case findKeywordIndex(cypher, "SHOW FUNCTIONS") == 0:
                // Must be at start (position 0) to be a standalone clause
                return e.executeShowFunctions(ctx, cypher)
        case findMultiWordKeywordIndex(cypher, "SHOW", "COMPOSITE DATABASES") == 0:
                // System command: SHOW COMPOSITE DATABASES (check before SHOW DATABASES)
                // Must be at start (position 0) to be a standalone clause
                return e.executeShowCompositeDatabases(ctx, cypher)
        case findMultiWordKeywordIndex(cypher, "SHOW", "CONSTITUENTS") == 0:
                // System command: SHOW CONSTITUENTS
                // Must be at start (position 0) to be a standalone clause
                return e.executeShowConstituents(ctx, cypher)
        case findMultiWordKeywordIndex(cypher, "SHOW", "DATABASES") == 0:
                // System command: SHOW DATABASES (plural - check before singular)
                // Must be at start (position 0) to be a standalone clause
                // Handles flexible whitespace: "SHOW DATABASES", "SHOW\tDATABASES", "SHOW\nDATABASES", etc.
                return e.executeShowDatabases(ctx, cypher)
        case findMultiWordKeywordIndex(cypher, "SHOW", "DATABASE") == 0:
                // System command: SHOW DATABASE (singular)
                // Must be at start (position 0) to be a standalone clause
                // Handles flexible whitespace: "SHOW DATABASE", "SHOW\tDATABASE", "SHOW\nDATABASE", etc.
                return e.executeShowDatabase(ctx, cypher)
        case findMultiWordKeywordIndex(cypher, "SHOW", "ALIASES") == 0:
                // System command: SHOW ALIASES
                // Must be at start (position 0) to be a standalone clause
                // Handles flexible whitespace: "SHOW ALIASES", "SHOW\tALIASES", "SHOW\nALIASES", etc.
                return e.executeShowAliases(ctx, cypher)
        case findMultiWordKeywordIndex(cypher, "ALTER", "COMPOSITE DATABASE") == 0:
                // System command: ALTER COMPOSITE DATABASE (check before ALTER DATABASE)
                // Must be at start (position 0) to be a standalone clause
                return e.executeAlterCompositeDatabase(ctx, cypher)
        case findMultiWordKeywordIndex(cypher, "ALTER", "DECAY PROFILE") == 0,
                findMultiWordKeywordIndex(cypher, "ALTER", "PROMOTION PROFILE") == 0,
                findMultiWordKeywordIndex(cypher, "ALTER", "PROMOTION POLICY") == 0:
                return e.executeKnowledgePolicyDDL(ctx, cypher)
        // Note: ALTER DATABASE is handled earlier (before SET check) to avoid routing conflict
        case findMultiWordKeywordIndex(cypher, "SHOW", "LIMITS") == 0:
                // System command: SHOW LIMITS
                // Must be at start (position 0) to be a standalone clause
                return e.executeShowLimits(ctx, cypher)
        default:
                firstWord := strings.Split(upperQuery, " ")[0]
                return nil, fmt.Errorf("unsupported query type: %s (supported: MATCH, CREATE, MERGE, DELETE, SET, REMOVE, RETURN, WITH, UNWIND, CALL, FOREACH, LOAD CSV, SHOW, DROP, ALTER)", firstWord)
        }
}

// executeReturn handles simple RETURN statements (e.g., "RETURN 1").
func (e *StorageExecutor) executeReturn(ctx context.Context, cypher string) (*ExecuteResult, error) {
        // Substitute parameters before processing
        if params := getParamsFromContext(ctx); params != nil {
                cypher = e.substituteParams(cypher, params)
        }

        // Parse RETURN clause - use word boundary detection
        returnIdx := findKeywordIndex(cypher, "RETURN")
        if returnIdx == -1 {
                return nil, fmt.Errorf("RETURN clause not found in query: %q", truncateQuery(cypher, 80))
        }

        returnClause := strings.TrimSpace(cypher[returnIdx+6:])
        // Strip trailing modifiers from RETURN projection (single-row RETURN path).
        // This prevents "ORDER BY ..." from being treated as an additional projection item.
        if cut := firstTopLevelModifierIndex(returnClause); cut >= 0 {
                returnClause = strings.TrimSpace(returnClause[:cut])
        }

        // Handle simple literal returns like "RETURN 1" or "RETURN true"
        parts := splitReturnExpressions(returnClause)
        columns := make([]string, 0, len(parts))
        values := make([]interface{}, 0, len(parts))

        for _, part := range parts {
                part = strings.TrimSpace(part)

                // Check for alias (AS)
                alias := part
                upperPart := strings.ToUpper(part)
                if asIdx := strings.Index(upperPart, " AS "); asIdx != -1 {
                        alias = strings.TrimSpace(part[asIdx+4:])
                        part = strings.TrimSpace(part[:asIdx])
                }

                columns = append(columns, alias)

                // Handle NULL literal explicitly first
                if strings.EqualFold(part, "null") {
                        values = append(values, nil)
                        continue
                }

                // Fabric APPLY correlated bindings (e.g., RETURN textKey, textKey128, texts).
                if isValidIdentifier(part) {
                        if v, ok := e.fabricRecordBindings[part]; ok {
                                values = append(values, v)
                                continue
                        }
                }

                // Try to evaluate as a function or expression first
                result := e.evaluateExpressionWithContext(ctx, part, nil, nil)
                if result != nil {
                        values = append(values, result)
                        continue
                }

                // Parse literal value
                if part == "1" || strings.HasPrefix(strings.ToLower(part), "true") {
                        values = append(values, int64(1))
                } else if part == "0" || strings.HasPrefix(strings.ToLower(part), "false") {
                        values = append(values, int64(0))
                } else if strings.HasPrefix(part, "'") && strings.HasSuffix(part, "'") {
                        values = append(values, part[1:len(part)-1])
                } else if strings.HasPrefix(part, "\"") && strings.HasSuffix(part, "\"") {
                        values = append(values, part[1:len(part)-1])
                } else {
                        // Try to parse as number
                        if val, err := strconv.ParseInt(part, 10, 64); err == nil {
                                values = append(values, val)
                        } else if val, err := strconv.ParseFloat(part, 64); err == nil {
                                values = append(values, val)
                        } else {
                                // Return as string
                                values = append(values, part)
                        }
                }
        }

        return &ExecuteResult{
                Columns: columns,
                Rows:    [][]interface{}{values},
        }, nil
}

func firstTopLevelModifierIndex(clause string) int {
        cut := -1
        for _, kw := range []string{"ORDER BY", "SKIP", "LIMIT"} {
                if idx := topLevelKeywordIndex(clause, kw); idx >= 0 && (cut == -1 || idx < cut) {
                        cut = idx
                }
        }
        return cut
}

// splitReturnExpressions splits RETURN expressions by comma, respecting parentheses and brackets depth
func splitReturnExpressions(clause string) []string {
        var parts []string
        var current strings.Builder
        parenDepth := 0
        bracketDepth := 0
        inQuote := false
        quoteChar := rune(0)

        for _, ch := range clause {
                switch {
                case (ch == '\'' || ch == '"') && !inQuote:
                        inQuote = true
                        quoteChar = ch
                        current.WriteRune(ch)
                case ch == quoteChar && inQuote:
                        inQuote = false
                        quoteChar = 0
                        current.WriteRune(ch)
                case ch == '(' && !inQuote:
                        parenDepth++
                        current.WriteRune(ch)
                case ch == ')' && !inQuote:
                        parenDepth--
                        current.WriteRune(ch)
                case ch == '[' && !inQuote:
                        bracketDepth++
                        current.WriteRune(ch)
                case ch == ']' && !inQuote:
                        bracketDepth--
                        current.WriteRune(ch)
                case ch == ',' && parenDepth == 0 && bracketDepth == 0 && !inQuote:
                        parts = append(parts, current.String())
                        current.Reset()
                default:
                        current.WriteRune(ch)
                }
        }

        if current.Len() > 0 {
                parts = append(parts, current.String())
        }

        return parts
}

// validateSyntax performs syntax validation.
// When NORNICDB_PARSER=antlr, uses ANTLR for strict OpenCypher grammar validation.
// When NORNICDB_PARSER=nornic (default), uses fast inline validation.
func (e *StorageExecutor) validateSyntax(cypher string) error {
        // Use ANTLR parser for validation when configured
        if config.IsANTLRParser() {
                return e.validateSyntaxANTLR(cypher)
        }
        return e.validateSyntaxNornic(cypher)
}

// validateSyntaxANTLR uses ANTLR for strict OpenCypher grammar validation.
// Provides detailed error messages with line/column information.
func (e *StorageExecutor) validateSyntaxANTLR(cypher string) error {
        return antlr.Validate(cypher)
}

// validateSyntaxNornic performs fast inline syntax validation.
func (e *StorageExecutor) validateSyntaxNornic(cypher string) error {
        if e.hasCachedValidSyntax(cypher) {
                return nil
        }
        if !hasValidStartKeyword(cypher) {
                return fmt.Errorf("syntax error: query must start with a valid clause (MATCH, CREATE, MERGE, DELETE, CALL, SHOW, EXPLAIN, PROFILE, ALTER, USE, BEGIN, COMMIT, ROLLBACK, etc.)")
        }

        // Check balanced parentheses
        parenCount := 0
        bracketCount := 0
        braceCount := 0
        inString := false
        stringChar := byte(0)

        for i := 0; i < len(cypher); i++ {
                c := cypher[i]

                if inString {
                        if c == stringChar && (i == 0 || cypher[i-1] != '\\') {
                                inString = false
                        }
                        continue
                }

                switch c {
                case '"', '\'':
                        inString = true
                        stringChar = c
                case '(':
                        parenCount++
                case ')':
                        parenCount--
                case '[':
                        bracketCount++
                case ']':
                        bracketCount--
                case '{':
                        braceCount++
                case '}':
                        braceCount--
                }

                if parenCount < 0 || bracketCount < 0 || braceCount < 0 {
                        return fmt.Errorf("syntax error: unbalanced brackets at position %d", i)
                }
        }

        if parenCount != 0 {
                return fmt.Errorf("syntax error: unbalanced parentheses")
        }
        if bracketCount != 0 {
                return fmt.Errorf("syntax error: unbalanced square brackets")
        }
        if braceCount != 0 {
                return fmt.Errorf("syntax error: unbalanced curly braces")
        }
        if inString {
                return fmt.Errorf("syntax error: unclosed quote")
        }

        e.markCachedValidSyntax(cypher)
        return nil
}

var validSyntaxStarts = [...]string{
        "MATCH", "CREATE", "MERGE", "DELETE", "DETACH", "CALL", "RETURN", "WITH",
        "UNWIND", "OPTIONAL", "DROP", "SHOW", "FOREACH", "LOAD", "EXPLAIN",
        "PROFILE", "ALTER", "USE", "BEGIN", "COMMIT", "ROLLBACK",
}

func hasValidStartKeyword(cypher string) bool {
        for _, start := range validSyntaxStarts {
                if startsWithKeywordFold(cypher, start) {
                        return true
                }
        }
        return false
}

// ensureSyntaxValidationCache lazily installs the syntax-validation cache
// pointer using sync.Once so concurrent CALL { ... } subqueries (which fan
// out via executeCallTailParallel) cannot race on the pointer write. The
// underlying cache itself is already mutex-guarded; the race was on the
// initial pointer assignment.
func (e *StorageExecutor) ensureSyntaxValidationCache() *syntaxValidationCache {
        e.syntaxValidationOnce.Do(func() {
                if e.syntaxValidationCache == nil {
                        e.syntaxValidationCache = &syntaxValidationCache{
                                cache: make(map[string]struct{}, 1024),
                                max:   4096,
                        }
                }
        })
        return e.syntaxValidationCache
}

func (e *StorageExecutor) hasCachedValidSyntax(cypher string) bool {
        if cypher == "" {
                return false
        }
        c := e.ensureSyntaxValidationCache()
        c.mu.RLock()
        _, ok := c.cache[cypher]
        c.mu.RUnlock()
        return ok
}

func (e *StorageExecutor) markCachedValidSyntax(cypher string) {
        if cypher == "" {
                return
        }
        c := e.ensureSyntaxValidationCache()
        c.mu.Lock()
        if len(c.cache) >= c.max {
                for k := range c.cache {
                        delete(c.cache, k)
                        break
                }
        }
        c.cache[cypher] = struct{}{}
        c.mu.Unlock()
}

orneryd / NornicDB / 28594755032

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