googleapis/mcp-toolbox · error

unable to scan row: %w

Error message

unable to scan row: %w

What it means

sqlite RunSQL (internal/sources/sqlite/sqlite.go:131) scans each result row into a slice of raw any values (using generic destinations because the sqlite driver lacks ColumnTypes). A scan failure is wrapped as "unable to scan row". This happens when the driver cannot convert a column value into *any, which is uncommon but can occur with driver-specific value handling errors.

Source

Thrown at internal/sources/sqlite/sqlite.go:131

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

	// The sqlite driver does not support ColumnTypes, so we can't get the
	// underlying database type of the columns. We'll have to rely on the
	// generic `any` type and then handle the JSON data separately.
	rawValues := make([]any, len(cols))
	values := make([]any, len(cols))
	for i := range rawValues {
		values[i] = &rawValues[i]
	}

	// Prepare the result slice
	out := []any{}
	for rows.Next() {
		if err := rows.Scan(values...); err != nil {
			return nil, fmt.Errorf("unable to scan row: %w", err)
		}

		// Create a map for this row
		row := orderedmap.Row{}
		for i, name := range cols {
			val := rawValues[i]
			// Handle nil values
			if val == nil {
				row.Add(name, nil)
				continue
			}
			// Handle JSON data
			if jsonString, ok := val.(string); ok {
				var unmarshaledData any
				if json.Unmarshal([]byte(jsonString), &unmarshaledData) == nil {
					row.Add(name, unmarshaledData)
					continue
				}

View on GitHub (pinned to 8cc6e09de2)

Solutions

1. Identify the offending row via the wrapped error and inspect that column's data
2. Cast problematic columns in SQL: SELECT CAST(bigblob_col AS TEXT) ...
3. Update the sqlite driver (modernc.org/sqlite or mattn/go-sqlite3) to the latest version
4. Run PRAGMA integrity_check to rule out database corruption

Example fix

// before
SELECT blob_data FROM files;
// after
SELECT CAST(blob_data AS TEXT) AS blob_data FROM files;

// pre-check unusual column values
row := db.QueryRow("SELECT typeof(col) FROM t LIMIT 1")
var t string
row.Scan(&t) // ensure the type is one your flow can handle

When it happens

Trigger: RunSQL where rows.Scan(values...) fails on a row — typically a driver conversion failure for an unusual column value/type, or a rows.Next/Scan state violation.

Common situations: Very large BLOB or nonstandard values; driver-specific scan bugs; corruption in a row; using a driver fork with different Scan semantics.

Related errors

• unable to parse row: %w
• unable to parse row: %w
• unable to parse row: %w
• unable to parse row: %w
• unable to parse row: %w

AI-assisted analysis of googleapis/mcp-toolbox@8cc6e09de2 (2026-09-05). Data as JSON: /api/errors/9065e05bed117ca0. Report an issue: GitHub.