googleapis/mcp-toolbox · error

error iterating rows: %w

Error message

error iterating rows: %w

What it means

sqlite RunSQL (internal/sources/sqlite/sqlite.go:158) checks rows.Err() after the iteration loop completes. A non-nil error means the row iteration itself failed partway (driver/connection error mid-stream), not that all rows were read successfully. The error is wrapped as "error iterating rows" and returned instead of the partial results.

Source

Thrown at internal/sources/sqlite/sqlite.go:158

				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
				}
			}
			// Store the value in the map
			row.Add(name, val)
		}
		out = append(out, row)
	}

	if err = rows.Err(); err != nil {
		return nil, fmt.Errorf("error iterating rows: %w", err)
	}

	return out, nil
}

func initSQLiteConnection(ctx context.Context, tracer trace.Tracer, name, dbPath string) (*sql.DB, error) {
	//nolint:all // Reassigned ctx
	ctx, span := sources.InitConnectionSpan(ctx, tracer, SourceType, name)
	defer span.End()

	// Open database connection
	db, err := sql.Open("sqlite", dbPath)
	if err != nil {
		return nil, fmt.Errorf("sql.Open: %w", err)
	}

	// Set some reasonable defaults for SQLite
	db.SetMaxOpenConns(1) // SQLite only supports one writer at a time

View on GitHub (pinned to 8cc6e09de2)

Solutions

1. Read the wrapped driver error to identify the underlying I/O or OOM condition
2. Reduce result set size with LIMIT or tighter WHERE clauses
3. Extend the context timeout if deadlines fire during large scans
4. Verify database file integrity and disk health (PRAGMA integrity_check, dmesg for I/O errors)

res, err := source.RunSQL(ctx, stmt, params)
if err != nil && strings.Contains(err.Error(), "error iterating rows") {
	// fail fast, alert on disk/IO health, optionally retry with LIMIT-reduced query
	return fmt.Errorf("sqlite iteration failed: %w", err)
}

When it happens

Trigger: RunSQL where rows.Err() is non-nil after the for rows.Next() loop: an I/O error reading from the database file mid-iteration, out-of-memory in the driver, or context cancellation while fetching rows.

Common situations: Database file removed or corrupted while a query streams; disk I/O errors; very large result sets hitting memory limits; context deadline expiring during iteration.

Related errors

• unable to read config file at %q: %w
• unable to access config folder at %q: %w
• failed to read Google tokeninfo response: %w
• failed to read object %q in bucket %q: %w
• failed to read response body: %w

AI-assisted analysis of googleapis/mcp-toolbox@8cc6e09de2 (2026-09-05). Data as JSON: /api/errors/009b55713bf4cb73. Report an issue: GitHub.