The error appears when an INSERT, UPDATE, or DELETE breaks a foreign-key relationship between parent and child tables.
Foreign key violation error occurs when a row operation breaks the required relationship between parent and child tables. Fix it by inserting the missing parent row, updating the child to a valid key, or deleting orphaned children, then re-running your statement.
ERROR: insert or update on table "child" violates foreign key constraint "child_parent_id_fkey"
Relational databases enforce referential integrity through foreign keys. A foreign key links a column in a child table to the primary key of a parent table. When that link is broken, the engine aborts the statement and throws a foreign key violation error.
The error appears during INSERT, UPDATE, or DELETE statements that would leave orphaned child rows or reference a non-existent parent.
Fixing it quickly keeps data consistent and prevents application failures.
Missing parent rows trigger the violation when you insert a child row whose foreign key value is not in the parent table. Updates that change a valid key to an invalid one cause the same issue.
Deleting a parent row without first removing or re-pointing its children also violates the constraint unless cascading rules are defined.
Finally, bulk loads or reorderings that ignore table dependencies generate violations.
Identify the failing statement and examine the foreign key column values. Insert the missing parent row, correct the child row value, or delete the orphaned child records.
If the parent delete caused the problem, either add ON DELETE CASCADE to the constraint or manually delete children before deleting the parent.
Always wrap fixes in transactions so you can roll back if needed.
ETL jobs often load child tables before parents. Load the parent first or disable constraints during load and re-check afterward.
Application-level race conditions delete parents while another session inserts children. Use foreign-key locks or wrap related operations in the same transaction to avoid the race.
Order inserts so parent tables load first.
Wrap multi-table changes in a single transaction to guarantee atomicity.
Add ON DELETE/ON UPDATE CASCADE or SET NULL where business logic permits. Monitor error logs and set alerts so teams act quickly.
Primary key violation: occurs when inserting duplicate keys; solve by ensuring uniqueness. Check constraint violation: arises when column values break a rule; adjust data or constraint.
Unique index violation: similar to primary key but on non-PK columns.
Constraint not found errors appear when referencing a dropped object; recreate or correct the reference.
Yes, but only for bulk loads; always re-enable and validate afterwards.
Minimal impact; cascading happens in-engine and is usually faster than manual deletes.
Rerun the query with RETURNING, use EXCEPTION blocks, or check the database error log.
Galaxy surfaces constraint metadata in the editor and warns when your query risks violating a foreign key.
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