googleapis/mcp-toolbox · error

unable to execute query: %w

Error message

unable to execute query: %w

What it means

Trino RunSQL wraps errors from QueryContext before any rows are read. QueryContext sends the statement to the Trino coordinator and fails on connectivity problems, auth rejection, SQL syntax/semantic errors, or an already-cancelled context. The driver error is preserved via %w.

Source

Thrown at internal/sources/trino/trino.go:119

	return false
}

func (s *Source) SourceType() string {
	return SourceType
}

func (s *Source) ToConfig() sources.SourceConfig {
	return s.Config
}

func (s *Source) TrinoDB() *sql.DB {
	return s.Pool
}

func (s *Source) RunSQL(ctx context.Context, statement string, params []any) (any, error) {
	results, err := s.TrinoDB().QueryContext(ctx, statement, params...)
	if err != nil {
		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 column names: %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]
	}

	out := []any{}
	for results.Next() {
		err := results.Scan(values...)

View on GitHub (pinned to 8cc6e09de2)

Solutions

1. Run the statement directly via trino-cli with the same user/catalog/schema to see the raw error
2. Check the wrapped error for Trino's error code (SYNTAX_ERROR, PERMISSION_DENIED, etc.)
3. Verify the configured catalog/schema and user grants in Trino
4. Increase queryTimeout and check context deadlines for long queries
5. Confirm coordinator is up and pool connections haven't been dropped by idle timeouts

Example fix

// before
results, err := db.QueryContext(ctx, "SELCT * FROM users")
// after
results, err := db.QueryContext(ctx, "SELECT * FROM users")

// pre-check grants/catalog with a cheap probe query
if err := probe(ctx, db, "SELECT 1"); err != nil { return err }

out, err := src.RunSQL(ctx, stmt, params)
if err != nil && strings.Contains(err.Error(), "unable to execute query") {
    var trinoErr *trino.Error
    if errors.As(err, &trinoErr) { log.Printf("trino code=%s msg=%s", trinoErr.Code, trinoErr.Message) }
}

When it happens

Trigger: Source.RunSQL where s.TrinoDB().QueryContext(ctx, statement, params...) fails: malformed SQL, unknown catalog/schema/table, permission denied, session expired, or network failure at submission time.

Common situations: Typos in SQL or referencing tables outside the configured catalog/schema; user lacking SELECT grants in Trino; stale pool connections after coordinator restart; query cancelled because the incoming request context expired.

Related errors

• unable to execute query: %w
• unable to execute query: %w
• errors encountered by results.Scan: %w
• unable to execute query: %w
• unable to execute query: %w

AI-assisted analysis of googleapis/mcp-toolbox@8cc6e09de2 (2026-09-05). Data as JSON: /api/errors/156c227568fc40ad. Report an issue: GitHub.