jackc/pgx · error

anyArrayArrayReflect: cannot scan array with length

Error message

anyArrayArrayReflect: cannot scan array with length %v into %v

What it means

Returned by anyArrayArrayReflect.SetDimensions when a one-dimensional PostgreSQL array's length differs from the length of the pre-existing destination slice. The reflect-based path can only fill an already-sized slice, not grow or shrink it.

Solutions

1. Scan into a fresh slice (nil or correctly sized) rather than a pre-populated one
2. Use a pointer-to-slice target so pgtype can allocate the right length

When it happens

Trigger: Thrown at pgtype/builtin_wrappers.go:940 when the library encounters an invalid state.

Common situations: See trigger scenarios.

AI-assisted analysis of jackc/pgx@ec1a0befd2 (2026-08-04). Data as JSON: /api/errors/9b1997de039854a8. Report an issue: GitHub.

Appendix: source

Thrown at pgtype/builtin_wrappers.go:940

func (a anyArrayArrayReflect) Index(i int) any {
	return a.array.Index(i).Interface()
}

func (a anyArrayArrayReflect) IndexType() any {
	return reflect.New(a.array.Type().Elem()).Elem().Interface()
}

func (a *anyArrayArrayReflect) SetDimensions(dimensions []ArrayDimension) error {
	if dimensions == nil {
		return fmt.Errorf("anyArrayArrayReflect: cannot scan NULL into %v", a.array.Type().String())
	}

	if len(dimensions) != 1 {
		return fmt.Errorf("anyArrayArrayReflect: cannot scan multi-dimensional array into %v", a.array.Type().String())
	}

	if int(dimensions[0].Length) != a.array.Len() {
		return fmt.Errorf("anyArrayArrayReflect: cannot scan array with length %v into %v", dimensions[0].Length, a.array.Type().String())
	}

	return nil
}

func (a *anyArrayArrayReflect) ScanIndex(i int) any {
	return a.array.Index(i).Addr().Interface()
}

func (a *anyArrayArrayReflect) ScanIndexType() any {
	return reflect.New(a.array.Type().Elem()).Interface()
}

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