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Ran 07 Jul 2026 02:19PM UTC

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Committed 07 Jul 2026 02:17PM UTC coverage: 90.016% (+0.05%) from 89.969%

Job # 28873360656.1

Build Type

Pull #9

github

Committed by

sandonemaki

Commit Message

perf: reuse per-row scan buffers in Row

The per-row scan path (scanCurrentRow, run once per row for every mapper
type and every query) allocated two slices on each row:

- scanDestinations was reallocated with make() purely to reset state,
  even though the before hook re-populates the same indices
  deterministically each row.
- createTargets allocated a fresh []any for rows.Scan on every row,
  even though drivers don't retain it past the Scan call.

Keep both slices on Row, allocated once in wrapRows, and reuse them each
row: zero scanDestinations in place (go.mod is go 1.18, so no clear()
builtin) and refill scanTargets — every index is overwritten each row,
so no stale values linger.

Safe because before(v) -> scanCurrentRow -> after(val) is synchronous
per row and columns are constant per query.

Wide-struct bench (11 cols, 100 rows):
  ScanAll: 520 -> 321 allocs/op (-38%), 134704 -> 88512 B/op (-34%)
  ScanOne:  16 -> 15 allocs/op,          2808 ->  2552 B/op

Pull Request Pull Request #9: perf: reuse per-row scan buffers in Row

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