gastownhall/beads · error

get blocking info: scan blocked-by: %w

Error message

get blocking info: scan blocked-by: %w

What it means

Returned by queryBlockedByInfo when a row of the blocked-by SELECT (issue_id, depends_on_id, type) cannot be scanned into three strings. Typically caused by NULL or non-string values in any of the three columns of dependencies/wisp_dependencies, or schema drift.

Source

Thrown at internal/storage/issueops/dependency_queries.go:627

			SELECT d.issue_id, %s AS depends_on_id, d.type
			FROM %s d
			WHERE d.issue_id IN (%s) AND d.type IN ('blocks', 'parent-child')
		`, depTargetExpr("d"), depTable, inClause)

		rows, err := tx.QueryContext(ctx, blockedByQuery, args...)
		if err != nil {
			if optionalBlockedTable(depTable) && isTableNotExistError(err) {
				continue
			}
			return fmt.Errorf("get blocked-by info from %s: %w", depTable, err)
		}
		var depRows []blockingInfoRow
		var blockerIDs []string
		for rows.Next() {
			var row blockingInfoRow
			if scanErr := rows.Scan(&row.issueID, &row.blockerID, &row.depType); scanErr != nil {
				_ = rows.Close()
				return fmt.Errorf("get blocking info: scan blocked-by: %w", scanErr)
			}
			depRows = append(depRows, row)
			blockerIDs = append(blockerIDs, row.blockerID)
		}
		_ = rows.Close()
		if err := rows.Err(); err != nil {
			return fmt.Errorf("get blocking info: blocked-by rows: %w", err)
		}

		statusByID, err := loadStatusByIDInTx(ctx, tx, blockerIDs)
		if err != nil {
			return fmt.Errorf("get blocking info: blocker status: %w", err)
		}
		for _, row := range depRows {
			if statusByID[row.blockerID] == types.StatusClosed {
				continue
			}
			if row.depType == "parent-child" {

View on GitHub (pinned to 71377f2769)

Solutions

1. Inspect the wrapped scan error to identify the failing column and value.
2. Find and repair rows with NULLs: SELECT * FROM <dep table> WHERE issue_id IS NULL OR type IS NULL OR depends_on_id IS NULL.
3. Re-run schema migrations to restore expected column definitions.
4. Restore the database from a known-good backup if rows are corrupted.
5. Align driver/server versions to avoid conversion differences.

Example fix

// before: dependency row with NULL type fails Scan
INSERT INTO dependencies (issue_id, depends_on_id, type) VALUES ('bd-1', 'bd-2', NULL);

// after: always set the required columns
INSERT INTO dependencies (issue_id, depends_on_id, type) VALUES ('bd-1', 'bd-2', 'blocks');

// Go: pre-check for unscannable (NULL) columns in dependency rows
var n int
if err := tx.QueryRowContext(ctx,
    "SELECT COUNT(*) FROM dependencies WHERE issue_id IS NULL OR depends_on_id IS NULL OR type IS NULL").Scan(&n); err != nil {
    return err
}
if n > 0 {
    return fmt.Errorf("%d dependency rows have NULL columns; repair first", n)
}

func isScanBlockedByError(err error) bool {
    return err != nil && strings.Contains(err.Error(), "scan blocked-by")
}

blockedBy, blocks, parents, err := GetBlockingInfoForIssuesInTx(ctx, tx, ids)
if err != nil && isScanBlockedByError(err) {
    // locate and repair the offending row before retrying
    return repairNullDependencyRows(ctx, tx)
}

When it happens

Trigger: Calling GetBlockingInfoForIssuesInTx when a dependency row has NULL issue_id, depends_on_id (per depTargetExpr), or type; or columns were altered to incompatible types by migration/hand-editing.

Common situations: Hand-edited or imported data with NULLs; partial schema migrations; rows restored from a mismatched-version backup; driver type-mapping differences after an upgrade.

Related errors

• get dependency counts: scan dependent: %w
• get dependency counts: scan blocker: %w
• failed to scan peer for migration: %w
• db: GetAllConfig: scan: %w
• db: GetCustomTypes: scan custom_types: %w

AI-assisted analysis of gastownhall/beads@71377f2769 (2026-08-30). Data as JSON: /api/errors/fb03334189767c8c. Report an issue: GitHub.