PostgreSQL raises foreign_key_violation (SQLSTATE 23503) when an INSERT, UPDATE, or DELETE breaks a declared foreign key constraint.
PostgreSQL Error 23503 (foreign_key_violation) means the row you are inserting, updating, or deleting would reference or orphan a parent row that does not exist. Insert the missing parent record first or change the child row to point to a valid parent to resolve the error.
PostgreSQL Error 23503
PostgreSQL raises SQLSTATE 23503 when a command violates a declared foreign key constraint. The constraint guarantees that every child row references a valid parent row, preserving referential integrity across tables.
This error stops INSERT, UPDATE, or DELETE statements that would create dangling references or orphan children.
Fixing it quickly is important because broken relationships lead to inconsistent data and failing application logic.
The most common trigger is inserting a child row before the required parent row exists.
An UPDATE that changes a foreign key column to a non-existent value or a DELETE that removes a parent row without ON DELETE support also produce 23503.
Other causes include disabled triggers, incorrect column ordering inside bulk loads, and race conditions across concurrent transactions that insert or delete related rows in the wrong order.
First, confirm the missing or orphaned parent row.
Insert the parent record, adjust the child row to reference an existing parent, or delete the invalid child. When deleting parents, add ON DELETE CASCADE or first remove child rows.
Wrap multi-table writes in a single transaction and order statements parent first, child second. If concurrent sessions interfere, add explicit locks or use DEFERRABLE INITIALLY DEFERRED constraints.
Bulk import files often load child tables first.
Adjust the import order or temporarily disable constraints, reload parents, then validate constraints with ALTER TABLE VALIDATE CONSTRAINT.
Soft-delete patterns that set deleted_at on parents need ON UPDATE triggers to null out or reassign child references. Without them, updates create the same violation.
Always insert parent rows before children and commit in one transaction.
Use ON DELETE CASCADE or ON DELETE SET NULL to handle parent removals gracefully.
Enable Galaxy’s AI copilot to analyze statement order and flag risky operations before execution. Galaxy’s version control makes it easy to review migrations that alter foreign keys.
Error 23502 not_null_violation occurs when a NOT NULL column receives NULL. Error 23505 unique_violation fires on duplicate key inserts. They differ in constraint type but share similar debugging patterns: inspect data, adjust statements, and enforce correct ordering.
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You can mark constraints DEFERRABLE and set them DEFERRED within a transaction. PostgreSQL will still validate at COMMIT, keeping data safe.
An index speeds up validation and cascading deletes but does not prevent the error itself. Always fix data ordering first.
Development often runs single-user tests. Production concurrency exposes race conditions where sessions insert or delete in conflicting orders.
Galaxy’s AI copilot analyzes your migration scripts, warns about missing insert order, and its transaction preview shows potential violations before execution.
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