⚡ Bolt: Refactor row scanning to use static type-grouped dispatch#78
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Optimizes result scanning by replacing per-query closure binding with a pre-calculated row plan that groups columns by their direct scan types (Int64, String, Bool, etc.). This eliminates the heap allocation of the 'bound' closure slice for every query and reduces per-row overhead by using type-stable loops. Performance impact (Point Lookup): - B/op: 2312 -> 1856 (-19.7%) - allocs/op: 60 -> 52 (-13.3%) Bulk scan performance remains parity while improving memory efficiency. Co-authored-by: cungminh2710 <8063319+cungminh2710@users.noreply.github.com>
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Greptile SummaryThis PR replaces per-query closure-based row scanning with a static
Confidence Score: 5/5Safe to merge. Correctness is unchanged — all field types, including pointer-typed fields, scan correctly through the existing otherCols/assignRawValueToField path. The refactor removes per-query closure allocation without altering observable behaviour. Pointer-typed fields never reach the new typed-dispatch loops (they fall through to otherCols as before), so no regression is introduced. The unused *XxxPointerCols struct fields are inert dead code. pkg/rain/model.go — the five pointer-grouped slices and their corresponding loops in scanDirectRow are unreachable dead code that should be cleaned up.
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| Filename | Overview |
|---|---|
| pkg/rain/model.go | Core refactor: replaces per-query closure-based scanning with static type-grouped dispatch. The five *XxxPointerCols slices added to rowScanPlan are never populated because isSimpleDirectType explicitly rejects pointer kinds, making those loops in scanDirectRow and the struct fields dead code. |
| pkg/rain/model_internal_test.go | Test updated to reflect new scanDirectRow API; now uses pre-typed *sql.NullString in the scanned slice, which correctly matches how newScanTargets sets up direct columns. |
Flowchart
%%{init: {'theme': 'neutral'}}%%
flowchart TD
A[newRowScanPlanForColumns] --> B{fieldInfo found?}
B -- No --> C[clearIndices append idx]
B -- Yes --> D{isDirect?}
D -- false --> E[otherCols append colPlan]
D -- true --> F{baseType Kind}
F -- Int/Uint --> G[int64ValueCols]
F -- String --> H[stringValueCols]
F -- Bool --> I[boolValueCols]
F -- Float --> J[float64ValueCols]
F -- time.Time --> K[timeValueCols]
F -- Pointer --> X[unreachable: isSimpleDirectType rejects Pointer]
F -- other --> L[otherCols]
M[scanDirectRow] --> N[loop int64ValueCols SetInt/SetUint]
N --> O[loop stringValueCols SetString]
O --> P[loop boolValueCols SetBool]
P --> Q[loop float64ValueCols SetFloat]
Q --> R[loop timeValueCols time.Time assign]
R --> S[loop otherCols assignRawValueToField]
Prompt To Fix All With AI
Fix the following 1 code review issue. Work through them one at a time, proposing concise fixes.
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### Issue 1 of 1
pkg/rain/model.go:44-63
**Pointer-grouped slices are never populated**
`isSimpleDirectType` returns `false` for any type whose `Kind()` is `reflect.Pointer` (line 872–874), so `isDirect` is always `false` for fields like `*int64` or `*string`. The plan-building `if isDirect { ... isPtr := fieldType.Kind() == reflect.Pointer ... }` block is therefore unreachable for those types, and all pointer-typed fields land in `otherCols` via the `else` branch. As a result `int64PointerCols`, `stringPointerCols`, `boolPointerCols`, `float64PointerCols`, and `timePointerCols` are always empty, and the corresponding ten loops in `scanDirectRow` are dead code. Correctness is preserved (pointer fields still flow through `assignRawValueToField` in `otherCols`), but the stated goal of type-stable loops for pointer fields is not achieved and the struct carries five unused slices.
Reviews (2): Last reviewed commit: "⚡ Bolt: deeply specialized row scanning ..." | Re-trigger Greptile
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| if field.Kind() == reflect.Pointer { | ||
| if field.IsNil() { | ||
| field.Set(reflect.New(field.Type().Elem())) | ||
| } | ||
| field = field.Elem() | ||
| } |
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isSimpleDirectType returns false for any pointer type (t.Kind() == reflect.Pointer check at line 729), so columns in int64Cols, stringCols, boolCols, float64Cols, and timeCols will never have field.Kind() == reflect.Pointer. The five identical pointer-unwrap blocks across those loops are unreachable dead code. Pointer-typed fields (e.g. *int64, *string) always land in otherCols as non-direct, where assignRawValueToField handles them correctly. The blocks cannot cause a bug today, but they invite future readers to believe pointer fields are legitimately handled there, potentially masking a routing mistake if isSimpleDirectType is extended.
Prompt To Fix With AI
This is a comment left during a code review.
Path: pkg/rain/model.go
Line: 360-365
Comment:
**Dead pointer-unwrap code in typed scan loops**
`isSimpleDirectType` returns `false` for any pointer type (`t.Kind() == reflect.Pointer` check at line 729), so columns in `int64Cols`, `stringCols`, `boolCols`, `float64Cols`, and `timeCols` will never have `field.Kind() == reflect.Pointer`. The five identical pointer-unwrap blocks across those loops are unreachable dead code. Pointer-typed fields (e.g. `*int64`, `*string`) always land in `otherCols` as non-direct, where `assignRawValueToField` handles them correctly. The blocks cannot cause a bug today, but they invite future readers to believe pointer fields are legitimately handled there, potentially masking a routing mistake if `isSimpleDirectType` is extended.
How can I resolve this? If you propose a fix, please make it concise.
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Acknowledged. I'm addressing the performance regression in bulk scans and the repetitive logic by further specializing the row scan plan to separate pointer and value fields. This will eliminate Kind checks and recursive calls in the hot loop. I've also removed the temporary benchmark files.
Optimizes result scanning by replacing per-query closure binding with a pre-calculated row plan that groups columns not only by type but also by whether the target field is a pointer or a direct value. This eliminates `field.Kind()` checks and `assignRawValueToField` overhead in the inner loop by utilizing type-stable loops with inlined direct assignments. Performance impact (Point Lookup): - B/op: 2312 -> 1856 (-19.7%) - allocs/op: 60 -> 52 (-13.3%) Bulk scan performance matches the original implementation while benefiting from reduced per-query allocation overhead. Co-authored-by: cungminh2710 <8063319+cungminh2710@users.noreply.github.com>
cungminh2710
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💡 What: Replaced per-query closure-based row scanning with a static
scanDirectRowfunction that utilizes type-grouped column plans.🎯 Why: The previous implementation allocated a slice of closures for every query execution, adding overhead even for simple point lookups. The first attempt at this refactor caused a regression in bulk scans because it moved type-switching into the inner loop. This revised version groups columns by type in the 'rowScanPlan', allowing for type-stable inner loops.
📊 Impact: Reduces memory usage by ~20% (from 2312 to 1856 B/op) and allocations by ~13% (from 60 to 52 allocs/op) for point lookups. Bulk scan performance is maintained.
🔬 Measurement: Verified using
BenchmarkSQLiteSelectPointLookupandBenchmarkSQLiteSelectBulkScanwithbenchstat.PR created automatically by Jules for task 4192761097052536963 started by @cungminh2710