What causes "failed to read composite fields: %w" in t8y2/dbx?

Re-check connectivity and retry; inspect the wrapped cause for the underlying DB error.

failed to read composite fields: %w

Error message

failed to read composite fields: %w

What it means

This error wraps a failure of the catalog query that reads composite type fields (attribute names, types, ordinals) for a composite custom type, returned by customTypeCompositeMembers when metadataQuery fails. Like the enum variant, the composite type row was found; only reading its member fields failed.

Source

Thrown at agents/drivers/vastbase-go/vastbase_metadata.go:748

	index := 0
	for rows.Next() {
		var label string
		var sortOrder float64
		if err := rows.Scan(&label, &sortOrder); err != nil {
			return nil, err
		}
		// enumsortorder is float4; ALTER TYPE ... ADD VALUE BEFORE/AFTER can
		// yield fractional values. Use the ORDER BY position for a unique key.
		index++
		members = append(members, customTypeMember{Ordinal: int32(index), EnumValue: &label})
	}
	return members, rows.Err()
}

func (s *server) customTypeCompositeMembers(sqlTemplate string, typrelid int64) ([]customTypeMember, error) {
	rows, err := s.metadataQuery(fmt.Sprintf(sqlTemplate, typrelid, typrelid))
	if err != nil {
		return nil, fmt.Errorf("failed to read composite fields: %w", err)
	}
	defer rows.Close()
	var members []customTypeMember
	for rows.Next() {
		var member customTypeMember
		var hasDefault bool
		var comment sql.NullString
		if err := rows.Scan(&member.Name, &member.DataType, &member.Ordinal, &member.Nullable, &hasDefault, &member.Default, &comment); err != nil {
			return nil, err
		}
		if !hasDefault {
			member.Default = nil
		}
		member.Comment = nullStringPtr(comment)
		members = append(members, member)
	}
	return members, rows.Err()
}

View on GitHub (pinned to c0390bff16)

Solutions

Re-check connectivity and retry; inspect the wrapped cause for the underlying DB error.
Grant the introspection role SELECT on pg_attribute/pg_type (or sys_catalog equivalents).
Ensure the driver's catalog mode (postgresCatalog flag) matches the target server.
If the wrapped error is structural (unknown column), update the driver or adjust catalog query templates.

Defensive patterns

Strategy: retry

Validate before calling

if err := db.Ping(); err != nil { return err }
var n int
if err := db.QueryRow("SELECT COUNT(*) FROM pg_attribute LIMIT 1").Scan(&n); err != nil {
    return fmt.Errorf("no catalog attribute access: %w", err)
}

Try / catch

details, err := srv.CustomTypeDetails(schema, name)
if err != nil && strings.Contains(err.Error(), "failed to read composite fields") {
    if isTransient(errors.Unwrap(err)) { /* retry with backoff */ }
}

Prevention

Ensure the introspection role can read pg_attribute/pg_type.
Retry transient network failures with backoff.
Verify driver/server version compatibility before large introspection jobs.

When it happens

Trigger: Requesting details of a composite type when the composite-members metadata query errors: connection loss, missing catalog privileges on pg_attribute/pg_type joins, or catalog query templates mismatched to the server (sys_catalog vs pg_catalog mode).

Common situations: Introspecting composite types with a limited-privilege role; transient network failures; running against a Vastbase build whose catalog layout differs from the assumed template.

Related errors

AI-assisted analysis of t8y2/dbx@c0390bff16 (2026-09-05). Data as JSON: /api/errors/e5baafeadfddd7a6. Report an issue: GitHub.