jackc/pgx · error

scan target type changed

Error message

scan target type changed

What it means

Sentinel ErrScanTargetTypeChanged: a cached scan plan was invoked with a destination whose concrete type no longer matches the type the plan was built for (e.g. a *bool plan receiving a *string). It guards against type confusion between plan selection and execution; the mismatched destination type is the faulty input and usually indicates a driver-internal caching bug rather than user error.

Solutions

1. If it surfaces in application code, report it as a pgx issue with the types involved
2. Ensure the same destination variable/type is used between Rows.Scan planning and scanning

When it happens

Trigger: Thrown at pgtype/pgtype.go:1171 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/bc8f80336d2307b3. Report an issue: GitHub.

Appendix: source

Thrown at pgtype/pgtype.go:1171

				codec = ByteaCodec{}
			}
		}
		return &pointerEmptyInterfaceScanPlan{codec: codec, m: m, oid: oid, formatCode: formatCode}
	}

	return &scanPlanFail{m: m, oid: oid, formatCode: formatCode}
}

func (m *Map) Scan(oid uint32, formatCode int16, src []byte, dst any) error {
	if dst == nil {
		return nil
	}

	plan := m.PlanScan(oid, formatCode, dst)
	return plan.Scan(src, dst)
}

var ErrScanTargetTypeChanged = errors.New("scan target type changed")

func codecScan(codec Codec, m *Map, oid uint32, format int16, src []byte, dst any) error {
	scanPlan := codec.PlanScan(m, oid, format, dst)
	if scanPlan == nil {
		return fmt.Errorf("PlanScan did not find a plan")
	}
	return scanPlan.Scan(src, dst)
}

func codecDecodeToTextFormat(codec Codec, m *Map, oid uint32, format int16, src []byte) (driver.Value, error) {
	if src == nil {
		return nil, nil
	}

	if format == TextFormatCode {
		return string(src), nil
	} else {
		value, err := codec.DecodeValue(m, oid, format, src)

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