27000ERRORTier 2 — Caution✅ HIGH confidence

triggered data change violation

Category: Triggered Data Change ViolationVersions: All Postgres versions

What this means

SQLSTATE 27000 is raised when a trigger or rule attempts to modify a table that is not allowed to be modified in the current trigger firing context — for example, modifying a table during a before-row trigger that is invoked by a foreign key constraint check.

Why it happens

1A trigger attempts to modify a table that is the subject of the triggering operation in a prohibited way
2A rule attempts a data modification that violates trigger-based constraints

How to reproduce

Trigger attempting to modify the triggering table in an illegal way.

trigger — this will ERROR

ERROR: triggered data change violation

Fix 1: Refactor trigger logic to avoid prohibited modifications

When a trigger causes 27000.

fix

Why this works

Review the trigger to ensure it does not modify tables in a way that violates the current execution context. Use AFTER triggers instead of BEFORE triggers for complex modifications, or use deferred constraints.

Sources

📚 Official docs: https://www.postgresql.org/docs/current/errcodes-appendix.html

🔧 Source ref: Class 27 — Triggered Data Change Violation

Confidence assessment

✅ HIGH confidence

Standard SQLSTATE. Rare in practice but well-defined.