googleapis/mcp-toolbox · error

errors encountered during query execution or row processing:

Error message

errors encountered during query execution or row processing: %w

What it means

This error is returned at the end of `RunSQL` when `results.Err()` reports a deferred error from row iteration or query execution. Unlike the immediate execution error, this catches failures that occur mid-stream — connection dropped while reading rows, context cancellation during iteration, or driver-level stream errors.

Source

Thrown at internal/sources/mssql/mssql.go:149

		}

		for results.Next() {
			scanErr := results.Scan(values...)
			if scanErr != nil {
				return nil, fmt.Errorf("unable to parse row: %w", scanErr)
			}
			row := orderedmap.Row{}
			for i, name := range cols {
				row.Add(name, rawValues[i])
			}
			out = append(out, row)
		}
	}

	// Check for errors from iterating over rows or from the query execution itself.
	// results.Close() is handled by defer.
	if err := results.Err(); err != nil {
		return nil, fmt.Errorf("errors encountered during query execution or row processing: %w", err)
	}

	return out, nil
}

func initMssqlConnection(
	ctx context.Context,
	tracer trace.Tracer,
	name, host, port, user, pass, dbname, encrypt string,
) (
	*sql.DB,
	error,
) {
	//nolint:all // Reassigned ctx
	ctx, span := sources.InitConnectionSpan(ctx, tracer, SourceType, name)
	defer span.End()

	userAgent, err := util.UserAgentFromContext(ctx)

View on GitHub (pinned to 8cc6e09de2)

Solutions

1. Unwrap the error and check for context.DeadlineExceeded / connection reset causes
2. Increase the context timeout or paginate large result sets (OFFSET/FETCH)
3. Enable connection retry/resilience (connection pool settings)
4. Check network stability and server logs for dropped connections

Example fix

// before (one huge query)
stmt := "SELECT * FROM big_table"
// after (paginated)
stmt := "SELECT * FROM big_table ORDER BY id OFFSET 0 ROWS FETCH NEXT 10000 ROWS ONLY"

func isTransientStreamErr(err error) bool {
    return errors.Is(err, context.DeadlineExceeded) ||
        errors.Is(err, io.ErrUnexpectedEOF) ||
        errors.Is(err, syscall.ECONNRESET)
}

res, err := src.RunSQL(ctx, stmt, nil)
if err != nil && strings.Contains(err.Error(), "row processing") {
    if errors.Is(err, context.DeadlineExceeded) {
        ctx2, cancel := context.WithTimeout(context.Background(), 5*time.Minute)
        defer cancel()
        res, err = src.RunSQL(ctx2, stmt, nil)
    }
}

When it happens

Trigger: Calling RunSQL when the connection drops partway through reading a large result set; context is cancelled while rows are still streaming; driver-level network errors during rows.Next() iteration.

Common situations: Timeouts on large SELECTs; network instability between client and SQL Server; server closing the connection (idle kill, failover) mid-result; context cancelled by an upstream request timeout.

Related errors

• errors encountered during row iteration: %w
• failed to fetch OIDC config: %w
• unable to execute query: %w
• unable to parse row: %w
• errors encountered during query execution or row processing:

AI-assisted analysis of googleapis/mcp-toolbox@8cc6e09de2 (2026-09-05). Data as JSON: /api/errors/edcec6bc0caa4198. Report an issue: GitHub.