jackc/pgx · error

number of field descriptions must equal number of values…

Error message

number of field descriptions must equal number of values, got %d and %d

What it means

Internal invariant in baseRows.Scan: the count of FieldDescriptions for the result does not match the count of values in the current row. Not caused by user arguments — it indicates a protocol desync, stale cached statement description, or driver bug, and the rows are marked fatal.

Solutions

1. Report upstream with the query and schema if reproducible
2. Try a different QueryExecMode to rule out stale cached descriptions
3. Close the connection and retry on a fresh one

When it happens

Trigger: Thrown at rows.go:241 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/b35dad2f49df44a7. Report an issue: GitHub.

Appendix: source

Thrown at rows.go:241

	}

	if rows.resultReader.NextRow() {
		rows.rowCount++
		rows.values = rows.resultReader.Values()
		return true
	} else {
		rows.Close()
		return false
	}
}

func (rows *baseRows) Scan(dest ...any) error {
	m := rows.typeMap
	fieldDescriptions := rows.FieldDescriptions()
	values := rows.values

	if len(fieldDescriptions) != len(values) {
		err := fmt.Errorf("number of field descriptions must equal number of values, got %d and %d", len(fieldDescriptions), len(values))
		rows.fatal(err)
		return err
	}

	if len(dest) == 1 {
		if rc, ok := dest[0].(RowScanner); ok {
			err := rc.ScanRow(rows)
			if err != nil {
				rows.fatal(err)
			}
			return err
		}
	}

	if len(fieldDescriptions) != len(dest) {
		err := fmt.Errorf("number of field descriptions must equal number of destinations, got %d and %d", len(fieldDescriptions), len(dest))
		rows.fatal(err)
		return err

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