stephenafamo / bob / 29178719639

48%

main: 48%

Build Type

Pull #736

github

Committed by sandonemaki

Commit Message

feat(orm): add opt-in PreloadDedup to share preloaded to-one instances

JOIN-based preloading builds one related struct per parent row, even when
many parents reference the same related row. Add an opt-in PreloadDedup
option (orm.PreloadDedup, wrapped by psql/mysql/sqlite PreloadDedup) that
caches related structs per query execution keyed by the join columns, so
parent rows with the same key share a single instance — the same sharing
semantics as ThenLoad, without changing the emitted SQL.

With the reflection-based StructMapper the key is read from the scan
destinations before the struct is built, so duplicate rows skip
construction, nested preload AfterMods and Collect entirely. With a typed
PreloadMapper the link is opaque, so the key is read from the built value:
instances are still shared and collected once, but construction still runs.
A last-key fast path handles sorted results with a single comparison.

Dedup disables itself when the join key columns are not selected
(PreloadOnly/PreloadExcept), never caches unmatched LEFT JOIN rows, and
turns itself off after 1024 distinct keys without a single cache hit as a
safety valve for workloads with no duplication.

Pull Request Pull Request #736: feat(orm): add opt-in PreloadDedup — share preloaded to-one instances across parent rows

Coverage Stats

208 of 265 new or added lines in 4 files covered. (78.49%)

8 existing lines in 1 file now uncovered.

12095 of 25117 relevant lines covered (48.15%)

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