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⚡ Bolt: reduce query execution allocations by removing redundant argument slice copies #97

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Merged
cungminh2710 merged 1 commit into from
Jun 1, 2026
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⚡ Bolt: reduce query execution allocations by removing redundant argument slice copies #97

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14 changes: 7 additions & 7 deletions pkg/rain/query_compile.go
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Original file line number Diff line number Diff line change
Expand Up @@ -34,20 +34,20 @@ func (q compiledQuery) literalArgs() ([]any, error) {
if q.hasNames {
return nil, ErrPreparedArgsRequired
}
// OPTIMIZATION: Return a fresh copy of the pre-calculated arguments to avoid
// shared state footguns if the caller modifies the slice, while still
// avoiding the overhead of rebuilding the slice from argPlan.
return append([]any(nil), q.args...), nil
// OPTIMIZATION: Return the pre-calculated arguments directly. Since q.args
// is a fresh slice created during compilation and query runners do not
// modify it, we can safely avoid the redundant copy.
return q.args, nil
Comment on lines +37 to +40
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@greptile-apps greptile-apps Bot Jun 1, 2026

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P2 Removed copy changes the slice-ownership contract for prepared queries

For prepared types (PreparedInsertQuery, PreparedUpdateQuery, PreparedDeleteQuery, PreparedSelectQuery), the compiledQuery is compiled once and stored in the struct; every subsequent call to Exec/Scan calls bind() on that stored value. With this change, the !hasNames fast-path now hands back a reference to the same backing array (p.compiled.args) on every call. That's safe today because no current caller writes to the returned slice before passing it to ExecContext/QueryContext. However, the old comment explicitly named this as protection against "shared state footguns", and removing it silently drops the guard. If any future code path modifies bound in-place between bind() and the DB call (e.g., driver-specific wrapping, middleware, or retry logic), it will corrupt the stored compiledQuery.args for all subsequent calls — a data-race-free but logically corrupting mutation with no immediate panic. A // NOTE: callers must not modify the returned slice comment would preserve the intent without the allocation cost.

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This is a comment left during a code review.
Path: pkg/rain/query_compile.go
Line: 37-40

Comment:
**Removed copy changes the slice-ownership contract for prepared queries**

For prepared types (`PreparedInsertQuery`, `PreparedUpdateQuery`, `PreparedDeleteQuery`, `PreparedSelectQuery`), the `compiledQuery` is compiled once and stored in the struct; every subsequent call to `Exec`/`Scan` calls `bind()` on that stored value. With this change, the `!hasNames` fast-path now hands back a reference to the same backing array (`p.compiled.args`) on every call. That's safe today because no current caller writes to the returned slice before passing it to `ExecContext`/`QueryContext`. However, the old comment explicitly named this as protection against "shared state footguns", and removing it silently drops the guard. If any future code path modifies `bound` in-place between `bind()` and the DB call (e.g., driver-specific wrapping, middleware, or retry logic), it will corrupt the stored `compiledQuery.args` for all subsequent calls — a data-race-free but logically corrupting mutation with no immediate panic. A `// NOTE: callers must not modify the returned slice` comment would preserve the intent without the allocation cost.

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Fix in Codex

}

func (q compiledQuery) bind(args PreparedArgs) ([]any, error) {
if !q.hasNames {
if len(args) > 0 {
return nil, fmt.Errorf("rain: unexpected prepared args for query without placeholders")
}
// OPTIMIZATION: Return a fresh copy of the pre-calculated arguments to avoid
// shared state footguns if the caller modifies the slice.
return append([]any(nil), q.args...), nil
// OPTIMIZATION: Return the pre-calculated arguments directly when there
// are no named placeholders to bind.
return q.args, nil
}

seen := make(map[string]struct{}, len(args))
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