googleapis/mcp-toolbox · error

errors encountered when converting values: %w

Error message

errors encountered when converting values: %w

What it means

After scanning, RunSQL converts each raw driver value to a Go type via mysqlcommon.ConvertToType using the column's type; if that conversion fails for any column, the whole RunSQL call fails with this wrapped error.

Source

Thrown at internal/sources/oceanbase/oceanbase.go:147

	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
			}

			// oceanbase uses mysql driver
			vMap[name], err = mysqlcommon.ConvertToType(colTypes[i], val)
			if err != nil {
				return nil, fmt.Errorf("errors encountered when converting values: %w", err)
			}
		}
		out = append(out, vMap)
	}

	if err := results.Err(); err != nil {
		return nil, fmt.Errorf("errors encountered during row iteration: %w", err)
	}

	return out, nil
}

func initOceanBaseConnectionPool(ctx context.Context, tracer trace.Tracer, name, host, port, user, pass, dbname, queryTimeout string) (*sql.DB, error) {
	_, span := sources.InitConnectionSpan(ctx, tracer, SourceType, name)
	defer span.End()

	dsn := fmt.Sprintf("%s:%s@tcp(%s:%s)/%s?parseTime=true", user, pass, host, port, dbname)

View on GitHub (pinned to 8cc6e09de2)

Solutions

1. Inspect the wrapped conversion error to find the offending column and type
2. Cast the problematic column in SQL to a well-supported type (CHAR, DECIMAL, DATETIME)
3. Pin/upgrade the mysql driver so type codes match what ConvertToType expects
4. Handle the column manually by selecting it as a string

Example fix

// before
SELECT created_ts FROM events;
// after
SELECT DATE_FORMAT(created_ts, '%Y-%m-%d %H:%i:%s') AS created_ts FROM events;

// ensure only converter-friendly types are selected
for _, col := range []string{"bit_col", "geom"} {
    if strings.Contains(sql, col) {
        sql = strings.Replace(sql, col, "CAST("+col+" AS CHAR)", 1)
    }
}

out, err := src.RunSQL(ctx, sql)
if err != nil && strings.Contains(err.Error(), "converting values") {
    // retry with string-cast columns
}

When it happens

Trigger: RunSQL returns rows whose driver values cannot be mapped by mysqlcommon.ConvertToType for the detected column type (unsupported type byte or malformed value).

Common situations: Legacy MySQL-driver type codes from OceanBase that the shared converter does not handle; corrupted or out-of-range temporal/numeric values; driver version mismatch between column type detection and converter support.

Related errors

• errors encountered when converting values: %w
• unable to create pool: %w
• unable to connect successfully: %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/11711c0bba9e35dc. Report an issue: GitHub.