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Improve Rows scan performance

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ScanContext reused between rows.Scan calls.
Simplified assign value logic.
Use complex destination for Rows test.
This commit is contained in:
go-jet 2022-02-04 12:31:08 +01:00
parent 4f29960378
commit c10244aeab
5 changed files with 114 additions and 84 deletions
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40
qrm/qrm.go
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@ -63,48 +63,28 @@ func Query(ctx context.Context, db DB, query string, args []interface{}, destPtr
}
// ScanOneRowToDest will scan one row into struct destination
func ScanOneRowToDest(rows *sql.Rows, destPtr interface{}) error {
func ScanOneRowToDest(scanContext *ScanContext, rows *sql.Rows, destPtr interface{}) error {
utils.MustBeInitializedPtr(destPtr, "jet: destination is nil")
utils.MustBe(destPtr, reflect.Ptr, "jet: destination has to be a pointer to slice or pointer to struct")
scanContext, err := newScanContext(rows)
if err != nil {
return fmt.Errorf("failed to create scan context, %w", err)
}
if len(scanContext.row) == 0 {
return errors.New("empty row slice")
}
err = rows.Scan(scanContext.row...)
err := rows.Scan(scanContext.row...)
if err != nil {
return fmt.Errorf("rows scan error, %w", err)
}
destinationPtrType := reflect.TypeOf(destPtr)
tempSlicePtrValue := reflect.New(reflect.SliceOf(destinationPtrType))
tempSliceValue := tempSlicePtrValue.Elem()
destValue := reflect.ValueOf(destPtr)
_, err = mapRowToSlice(scanContext, "", newTypeStack(), tempSlicePtrValue, nil)
_, err = mapRowToStruct(scanContext, "", newTypeStack(), destValue, nil)
if err != nil {
return fmt.Errorf("failed to map a row, %w", err)
}
// edge case when row result set contains only NULLs.
if tempSliceValue.Len() == 0 {
return nil
}
destValue := reflect.ValueOf(destPtr).Elem()
firstTempSliceValue := tempSliceValue.Index(0).Elem()
if destValue.Type().AssignableTo(firstTempSliceValue.Type()) {
destValue.Set(tempSliceValue.Index(0).Elem())
}
return nil
}
@ -120,7 +100,7 @@ func queryToSlice(ctx context.Context, db DB, query string, args []interface{},
}
defer rows.Close()
scanContext, err := newScanContext(rows)
scanContext, err := NewScanContext(rows)
if err != nil {
return
@ -157,7 +137,7 @@ func queryToSlice(ctx context.Context, db DB, query string, args []interface{},
}
func mapRowToSlice(
scanContext *scanContext,
scanContext *ScanContext,
groupKey string,
typesVisited *typeStack,
slicePtrValue reflect.Value,
@ -204,7 +184,7 @@ func mapRowToSlice(
return
}
func mapRowToBaseTypeSlice(scanContext *scanContext, slicePtrValue reflect.Value, field *reflect.StructField) (updated bool, err error) {
func mapRowToBaseTypeSlice(scanContext *ScanContext, slicePtrValue reflect.Value, field *reflect.StructField) (updated bool, err error) {
index := 0
if field != nil {
typeName, columnName := getTypeAndFieldName("", *field)
@ -226,7 +206,7 @@ func mapRowToBaseTypeSlice(scanContext *scanContext, slicePtrValue reflect.Value
}
func mapRowToStruct(
scanContext *scanContext,
scanContext *ScanContext,
groupKey string,
typesVisited *typeStack, // to prevent circular dependency scan
structPtrValue reflect.Value,
@ -308,7 +288,7 @@ func mapRowToStruct(
}
func mapRowToDestinationValue(
scanContext *scanContext,
scanContext *ScanContext,
groupKey string,
typesVisited *typeStack,
dest reflect.Value,
@ -340,7 +320,7 @@ func mapRowToDestinationValue(
}
func mapRowToDestinationPtr(
scanContext *scanContext,
scanContext *ScanContext,
groupKey string,
typesVisited *typeStack,
destPtrValue reflect.Value,