perf(db): eliminate closure allocation in getMemTables cleanup#2291
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shaunpatterson wants to merge 1 commit into
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perf(db): eliminate closure allocation in getMemTables cleanup#2291shaunpatterson wants to merge 1 commit into
shaunpatterson wants to merge 1 commit into
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getMemTables previously returned (tables, cleanupFunc) where cleanupFunc was a closure capturing the tables slice. That closure escaped to the heap on every call (one extra allocation per iterator construction in the rollup path). Split into: func (db *DB) getMemTables() []*memTable func decrMemTables([]*memTable) Callers do `defer decrMemTables(tables)` after the getMemTables call. The slice is fully populated before the defer evaluates its argument, so the captured slice header points to the correct backing array; no behavioral change. decrMemTables is a free function (no receiver) so the deferred call record doesn't pay for a *DB pointer alongside the slice header. Saves 1 alloc and 32 B per iterator construction on BenchmarkRollupKeyIterator: before: 801 B/op, 14 allocs/op after: 769 B/op, 13 allocs/op Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>
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Summary
getMemTablespreviously returned(tables, cleanupFunc)wherecleanupFuncwas a closure capturing thetablesslice. That closure escaped to the heap on every call — one extra allocation per iterator construction in the rollup path.Split into:
Callers do
defer decrMemTables(tables)after thegetMemTablescall. The slice is fully populated before the defer evaluates its argument, so the captured slice header points to the correct backing array; no behavioral change.decrMemTablesis a free function (no receiver) so the deferred call record doesn't pay for a*DBpointer alongside the slice header.Benchmark — BenchmarkRollupKeyIterator
Test plan
go test ./...passesdb.get,txn.NewIterator,stream_writer) verified to release refs via defer🤖 Generated with Claude Code