Add RowsColumnScanner support (Go 1.27+)

[Copilot]

Implements the driver.RowsColumnScanner interface introduced in Go 1.27, which allows drivers to scan row data directly into user-provided destinations, bypassing the intermediate driver.Value allocation path.

Changes

• rows.go (//go:build go1.27): Contains the full mysqlRows struct (with currentRow []driver.Value field to cache decoded values for the current row) plus all existing row methods and the new RowsColumnScanner implementation:
  • (*binaryRows).NextRow() / (*textRows).NextRow() — reads the next row into currentRow, reallocating only when column count changes (e.g. after NextResultSet)
  • (*mysqlRows).ScanColumn(scanCtx, i, dest) — delegates to sql.ConvertAssign with a bounds check
• rows_before_go127.go (//go:build !go1.27): Contains the original mysqlRows struct and all existing row methods for pre-1.27 builds (no RowsColumnScanner support).

When Go 1.27+ is used, database/sql automatically prefers NextRow + ScanColumn over Next([]driver.Value). For older Go versions, behavior is unchanged.

[coveralls]

coverage: 82.731% (-0.07%) from 82.804% — copilot/support-rows-column-scanner into master

[methane]

@copilot Go <1.27 で currentRow が使われていないというエラーになります。
rows_column_scanner.go を作るのをやめて、 rows.go の中で実装してください。
Go <1.27 で使われない関数があるのは気にしません。

[Copilot]

Fixed in the latest commit. Since driver.ScanContext only exists in Go 1.27+, rows.go now carries //go:build go1.27 and contains all rows code plus the NextRow/ScanColumn methods. A new rows_before_go127.go with //go:build !go1.27 covers pre-1.27 builds (same structure as the existing conncheck.go / conncheck_dummy.go pattern). rows_column_scanner.go has been deleted.