joaoh82 / rust_sqlite / 25632443257

69%

Build Type

push

github

Committed by web-flow

Commit Message

feat(engine): Phase 11.4 BEGIN CONCURRENT writes + commit-time validation (SQLR-22) (#125)

The headline slice of Phase 11. Multiple sibling Connections can
each hold their own open BEGIN CONCURRENT transaction; commits
validate against MvStore and abort with SQLRiteError::Busy on
row-level write-write conflict. The four plan-required tests
pass: disjoint inserts both commit, same-row updates collide and
one wins, aborted writes never become visible, retry-after-Busy
succeeds.

New `sqlrite::mvcc::transaction::ConcurrentTx` (per-Connection):
- TxHandle (RAII registry entry, drops at COMMIT/ROLLBACK)
- tables: HashMap<String, Table> — working state, swapped with
  db.tables for the duration of each statement's executor pass
- tables_at_begin: HashMap<String, Table> — immutable BEGIN-time
  clone, used at COMMIT to derive the write-set without seeing
  other transactions' commits as bogus DELETEs
- schema_at_begin: Vec<String> — sorted table-name fingerprint

Connection wiring:
- New concurrent_tx: Option<ConcurrentTx> field — per-handle so
  N siblings can each carry their own open tx.
- Connection::execute pre-parses for BEGIN CONCURRENT / COMMIT /
  ROLLBACK before sqlparser runs (sqlparser 0.61 doesn't have a
  Concurrent modifier; same intercept pattern as PRAGMA).
- begin_concurrent: pre-conditions (journal_mode = mvcc, no
  active tx, not read-only) → ConcurrentTx::begin → store.
- execute_in_concurrent_tx: rejects DDL via string-prefix check;
  std::mem::swap(db.tables, tx.tables); parks dummy TxnSnapshot
  on db.txn to suppress auto-save; runs process_command;
  unwinds in reverse. Executor itself unchanged.
- commit_concurrent: schema_unchanged check; diff_tables_for_writes
  against tx.tables_at_begin; validation walks MvStore for
  latest_committed_begin per row; if any > begin_ts → Busy with
  rollback semantics. On success: tick clock for commit_ts; push
  committed versions; per-row apply (delete_row + restore_row) to
  db.tables; save_da... (continued)

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