⚡ Bolt: Argument Capacity Hinting for Complex Expressions

[cungminh2710]

💡 What

Implement argument capacity hints for complex expressions in the query compiler.

🎯 Why

Rendering expressions like `IN`, `CASE`, or large raw SQL fragments often appends multiple values to the query's `args` and `argPlan` slices. Without a hint, these slices may undergo multiple re-allocations and copies as they grow.

📊 Impact

• `BenchmarkSelectToSQL/Complex`: Reduces execution time from ~2580 ns/op to ~2413 ns/op (~6% improvement).
• `BenchmarkInsertToSQL/BulkInsert1000Rows`: Reduces execution time from ~306935 ns/op to ~281289 ns/op (~8% improvement).
• Improved efficiency for relation loading and bulk operations by minimizing GC pressure from slice re-allocations.

🔬 Measurement

Verified using `go test -bench . ./pkg/rain/`. Existing tests and linting pass correctly.

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PR created automatically by Jules for task 14598586172250427527 started by @cungminh2710

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[greptile-apps]

Greptile Summary

This PR adds argument capacity hints via ensureArgsCapacity before rendering complex SQL expressions (IN, BETWEEN, CASE, CONCAT, COALESCE, LogicalExpr, BinaryExpr, RawExpr), and hoists the expressionContext creation outside the InExpr value loop to eliminate redundant per-iteration struct initialization.

• Capacity hints are added at the start of each expression case to pre-allocate args/argPlan slices, reducing re-allocations for large expressions like bulk IN predicates.
• The InExpr loop optimization correctly hoists the exprCtx computation outside the loop; since expressionContext has no pointer fields and is passed by value, this is semantically identical to the original while avoiding repeated struct allocations.

Confidence Score: 4/5

Safe to merge — all changes are additive capacity hints and a loop hoisting refactor with no correctness risk.

The BinaryExpr hint of 1 for a two-operand expression leaves a small allocation gap when both operands are bound parameters; all other hints are accurate or conservative, and the InExpr loop refactor is semantically identical to the original.

pkg/rain/query_compile.go — the BinaryExpr capacity hint on line 401 is worth a second look.

Important Files Changed

Filename	Overview
pkg/rain/query_compile.go	Adds ensureArgsCapacity calls before complex expressions and hoists InExpr context creation outside the loop. The BinaryExpr hint of 1 is a slight underestimate for two-operand expressions; the InExpr loop refactor is semantically correct.
.jules/bolt.md	Documentation-only update recording the new learning about argument capacity hinting for complex expressions. No code impact.

Flowchart

%%{init: {'theme': 'neutral'}}%%
flowchart TD
    A["writeExpressionInContext(expr)"] --> B{expr type?}
    B -->|BinaryExpr| C["ensureArgsCapacity(1)\nwriteExpression(Left)\nwriteExpression(Right)"]
    B -->|ConcatExpr| D["ensureArgsCapacity(len(Exprs))\nwrite each expr"]
    B -->|InExpr| E["ensureArgsCapacity(len(Values))\nhoist exprCtx outside loop\nwrite each value"]
    B -->|BetweenExpr| F["ensureArgsCapacity(2)\nwriteExpression(Left/Start/End)"]
    B -->|LogicalExpr| G["ensureArgsCapacity(len(Exprs))\nwrite each predicate"]
    B -->|CaseExpr| H["hint = pairs×2 + optional\nensureArgsCapacity(hint)\nwrite WHEN/THEN/ELSE"]
    B -->|CoalesceExpr| I["ensureArgsCapacity(len(Exprs))\nwrite each expr"]
    B -->|RawExpr| J["ensureArgsCapacity(len(Args))\nparse SQL ? placeholders"]
    C --> K["c.args appended via writeAny"]
    D --> K
    E --> K
    F --> K
    G --> K
    H --> K
    I --> K
    J --> K

Loading

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flowchart TD
    A["writeExpressionInContext(expr)"] --> B{expr type?}
    B -->|BinaryExpr| C["ensureArgsCapacity(1)\nwriteExpression(Left)\nwriteExpression(Right)"]
    B -->|ConcatExpr| D["ensureArgsCapacity(len(Exprs))\nwrite each expr"]
    B -->|InExpr| E["ensureArgsCapacity(len(Values))\nhoist exprCtx outside loop\nwrite each value"]
    B -->|BetweenExpr| F["ensureArgsCapacity(2)\nwriteExpression(Left/Start/End)"]
    B -->|LogicalExpr| G["ensureArgsCapacity(len(Exprs))\nwrite each predicate"]
    B -->|CaseExpr| H["hint = pairs×2 + optional\nensureArgsCapacity(hint)\nwrite WHEN/THEN/ELSE"]
    B -->|CoalesceExpr| I["ensureArgsCapacity(len(Exprs))\nwrite each expr"]
    B -->|RawExpr| J["ensureArgsCapacity(len(Args))\nparse SQL ? placeholders"]
    C --> K["c.args appended via writeAny"]
    D --> K
    E --> K
    F --> K
    G --> K
    H --> K
    I --> K
    J --> K

Loading

Prompt To Fix All With AI

Fix the following 1 code review issue. Work through them one at a time, proposing concise fixes.

---

### Issue 1 of 1
pkg/rain/query_compile.go:401-403
`BinaryExpr` renders two sub-expressions (`Left` and `Right`), so a hint of `1` will under-allocate whenever both operands produce a bound argument — e.g. `? + ?` or a compound expression on each side. The hint should be `2` to match the actual operand count, consistent with how `BetweenExpr` accounts for two value operands.

```suggestion
		c.ensureArgsCapacity(2)
		c.writeByte('(')
		if err := c.writeExpression(value.Left); err != nil {
```

_{Reviews (1): Last reviewed commit: "perf(rain): add argument capacity hints ..." | Re-trigger Greptile}

[greptile-apps]

BinaryExpr renders two sub-expressions (Left and Right), so a hint of 1 will under-allocate whenever both operands produce a bound argument — e.g. ? + ? or a compound expression on each side. The hint should be 2 to match the actual operand count, consistent with how BetweenExpr accounts for two value operands.

Suggested change

	c.ensureArgsCapacity(1)
	c.writeByte('(')
	if err := c.writeExpression(value.Left); err != nil {
	c.ensureArgsCapacity(2)
	c.writeByte('(')
	if err := c.writeExpression(value.Left); err != nil {

Prompt To Fix With AI

This is a comment left during a code review.
Path: pkg/rain/query_compile.go
Line: 401-403

Comment:
`BinaryExpr` renders two sub-expressions (`Left` and `Right`), so a hint of `1` will under-allocate whenever both operands produce a bound argument — e.g. `? + ?` or a compound expression on each side. The hint should be `2` to match the actual operand count, consistent with how `BetweenExpr` accounts for two value operands.

```suggestion
		c.ensureArgsCapacity(2)
		c.writeByte('(')
		if err := c.writeExpression(value.Left); err != nil {
```

How can I resolve this? If you propose a fix, please make it concise.