googleapis/mcp-toolbox · error

unable to get column types: %w

Error message

unable to get column types: %w

What it means

RunSQL wraps results.ColumnTypes() errors with this message. ColumnTypes() fetches per-column type information needed to convert raw driver values into Go types (via ConvertToType); failure indicates the result set metadata could not be fully retrieved from the driver.

Source

Thrown at internal/sources/singlestore/singlestore.go:136

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

	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]
	}
	defer results.Close()

	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 {
			val := rawValues[i]
			if val == nil {
				vMap[name] = nil
				continue
			}

			vMap[name], err = mysqlcommon.ConvertToType(colTypes[i], val)
			if err != nil {

View on GitHub (pinned to 8cc6e09de2)

Solutions

1. Inspect the wrapped driver error for the precise protocol/network cause.
2. Retry the query to rule out a transient connection drop.
3. Check network path (load balancers, proxies) for idle/short timeouts and raise them.
4. Confirm the SingleStore server version is supported by the MySQL driver in use.
5. If reproducible for a specific statement, simplify the query's column expressions to isolate the offending type.

out, err := source.RunSQL(ctx, stmt, params)
if err != nil && strings.Contains(err.Error(), "unable to get column types") {
    // log and retry once; fall back to a simpler SELECT if persistent
    out, err = source.RunSQL(ctx, simplifiedStmt, params)
}
if err != nil { return err }

When it happens

Trigger: After Columns() succeeds, results.ColumnTypes() returns an error — usually the same class of connection/protocol failure as Columns(), e.g. the connection died while fetching extended column type metadata.

Common situations: Mid-query network failure, server closed the connection, driver/protocol mismatch with an unusual column type, or a proxy truncating the response.

Related errors

• unable to retrieve rows column name: %w
• unable to parse row: %w
• errors encountered when converting values: %w
• unable to execute query: %w
• errors encountered during row iteration: %w

AI-assisted analysis of googleapis/mcp-toolbox@8cc6e09de2 (2026-09-05). Data as JSON: /api/errors/4555278206b9a18e. Report an issue: GitHub.