googleapis/mcp-toolbox · error

unable to get column types: %w

Error message

unable to get column types: %w

What it means

RunSQL calls results.ColumnTypes() to map ClickHouse-specific types (e.g. String/FixedString) for value handling. If the driver cannot return column types, this error wraps the cause.

Source

Thrown at internal/sources/clickhouse/clickhouse.go:133

		return nil, fmt.Errorf("unable to execute query: %w", err)
	}
	defer results.Close()

	cols, err := results.Columns()
	if err != nil {
		return nil, fmt.Errorf("unable to retrieve rows column name: %w", err)
	}

	// create an array of values for each column, which can be re-used to scan each row
	rawValues := make([]any, len(cols))
	values := make([]any, len(cols))
	for i := range rawValues {
		values[i] = &rawValues[i]
	}

	colTypes, err := results.ColumnTypes()
	if err != nil {
		return nil, fmt.Errorf("unable to get column types: %w", err)
	}

	out := []any{}
	for results.Next() {
		err := results.Scan(values...)
		if err != nil {
			return nil, fmt.Errorf("unable to parse row: %w", err)
		}
		vMap := make(map[string]any)
		for i, name := range cols {
			// ClickHouse driver may return specific types that need handling
			switch colTypes[i].DatabaseTypeName() {
			case "String", "FixedString":
				if rawValues[i] != nil {
					// Handle potential []byte to string conversion if needed
					if b, ok := rawValues[i].([]byte); ok {
						vMap[name] = string(b)
					} else {

View on GitHub (pinned to 8cc6e09de2)

Solutions

1. Read the wrapped error for the driver's root cause.
2. Check connection stability and retry the query.
3. Verify the clickhouse-go driver version is compatible with the server.
4. Ensure nothing concurrently closes the results.

rows, err := src.RunSQL(ctx, stmt)
if err != nil {
    if strings.Contains(err.Error(), "unable to get column types") {
        return retryWithBackoff(ctx, stmt)
    }
    return err
}

When it happens

Trigger: Calling results.ColumnTypes() fails after a successful Columns() call — usually due to a broken result stream or driver state error.

Common situations: Connection failure mid-query, driver/driver-version incompatibility, results closed prematurely.

Related errors

• unable to execute query: %w
• unable to retrieve rows column name: %w
• unable to parse rows: %w
• unable to create pool: %w
• unable to connect successfully: %w

AI-assisted analysis of googleapis/mcp-toolbox@8cc6e09de2 (2026-09-05). Data as JSON: /api/errors/af884e83da5ac8de. Report an issue: GitHub.