Unknown field for composite type %q: field %q (OID %v) is n

Error message

Unknown field for composite type %q:  field %q (OID %v) is not already registered.

What it means

Error "Unknown field for composite type %q: field %q (OID %v) is not already registered." thrown in jackc/pgx.

Source

Thrown at derived_types.go:204

		ti := derivedTypeInfo{}
		err = rows.Scan(&ti.TypeName, &ti.NspName, &ti.Typtype, &ti.Typbasetype, &ti.Typelem, &ti.Oid, &ti.Rngtypid, &ti.Rngsubtype, &ti.Attnames, &ti.Atttypids)
		if err != nil {
			return nil, fmt.Errorf("While scanning type information: %w", err)
		}
		var type_ *pgtype.Type
		switch ti.Typtype {
		case "b": // array
			dt, ok := m.TypeForOID(ti.Typelem)
			if !ok {
				return nil, fmt.Errorf("Array element OID %v not registered while loading pgtype %q", ti.Typelem, ti.TypeName)
			}
			type_ = &pgtype.Type{Name: ti.TypeName, OID: ti.Oid, Codec: &pgtype.ArrayCodec{ElementType: dt}}
		case "c": // composite
			var fields []pgtype.CompositeCodecField
			for i, fieldName := range ti.Attnames {
				dt, ok := m.TypeForOID(ti.Atttypids[i])
				if !ok {
					return nil, fmt.Errorf("Unknown field for composite type %q:  field %q (OID %v) is not already registered.", ti.TypeName, fieldName, ti.Atttypids[i])
				}
				fields = append(fields, pgtype.CompositeCodecField{Name: fieldName, Type: dt})
			}

			type_ = &pgtype.Type{Name: ti.TypeName, OID: ti.Oid, Codec: &pgtype.CompositeCodec{Fields: fields}}
		case "d": // domain
			dt, ok := m.TypeForOID(ti.Typbasetype)
			if !ok {
				return nil, fmt.Errorf("Domain base type OID %v was not already registered, needed for %q", ti.Typbasetype, ti.TypeName)
			}

			type_ = &pgtype.Type{Name: ti.TypeName, OID: ti.Oid, Codec: dt.Codec}
		case "e": // enum
			type_ = &pgtype.Type{Name: ti.TypeName, OID: ti.Oid, Codec: &pgtype.EnumCodec{}}
		case "r": // range
			dt, ok := m.TypeForOID(ti.Rngsubtype)
			if !ok {
				return nil, fmt.Errorf("Range element OID %v was not already registered, needed for %q", ti.Rngsubtype, ti.TypeName)

View on GitHub (pinned to ec1a0befd2)

When it happens

Trigger: Thrown at derived_types.go:204 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: /data/errors/a39459415b2b3a1e.json. Report an issue: GitHub.