could not create exclusion constraint “…”

Symptoms

A statement failed with SQLSTATE 23P01 (exclusion_violation), reported at severity ERROR. This is a Integrity Constraint Violation condition: PostgreSQL emits the message could not create exclusion constraint "…".

• The client receives SQLSTATE 23P01 (exclusion violation).
• The operation is rejected at ERROR level; the statement does not complete.
• The server adds a DETAIL line with specifics (see below).

What the server log shows

ERROR:  could not create exclusion constraint "…"
DETAIL:  Key … conflicts with key ….

Why PostgreSQL raises this

Class 23 (Integrity Constraint Violation) is raised when a write would break a declared constraint — NOT NULL, CHECK, UNIQUE/primary key, foreign key, or exclusion.

As described in PostgreSQL’s Section 5.4 Constraints and Appendix A (PostgreSQL Error Codes), SQLSTATE 23P01 carries the condition name exclusion_violation in class Integrity Constraint Violation. (Paraphrased — see the linked reference for the exact wording.)

Common causes

• A duplicate value violated a unique or primary-key constraint.
• A referencing row had no matching parent (foreign key).
• A NOT NULL column received NULL, or a CHECK predicate failed.
• An exclusion constraint rejected overlapping values.

How to fix it

1. Identify the offending row and reconcile it with the constraint.
2. Insert or fix the referenced parent row before the child.
3. Use ON CONFLICT to handle duplicates intentionally.
4. Review the constraint definition to confirm it matches the data model.

Version applicability

This message is present in PostgreSQL 15, 16, 17, 18 and 19.

Related & next steps

• SQLSTATE 23P01 — Exclusion Violation (full reference)
• PostgreSQL error code index

Reference: PostgreSQL Section 5.4 Constraints.