EC
P0004
PostgreSQLERRORNotablePL/pgSQL ErrorHIGH confidence

assert_failure

What this means

A PL/pgSQL ASSERT statement evaluated its condition as false, causing the function to abort. Used for invariant checking and developer assertions in PL/pgSQL code.

Why it happens
  1. 1ASSERT condition evaluated to false or NULL
  2. 2Invariant assumed by the developer is violated by actual data or state
  3. 3ASSERT used as a debugging tool and left in production code with an edge case not anticipated
How to reproduce

PL/pgSQL function or DO block containing an ASSERT statement whose condition fails

trigger — this will error
trigger — this will error
DO $
DECLARE
  total int;
BEGIN
  SELECT count(*) INTO total FROM orders;
  ASSERT total > 0, 'orders table must not be empty';
END;
$;

expected output

ERROR:  P0004: orders table must not be empty

Fix 1

Fix the condition that caused the assertion to fail

WHEN The assertion represents a genuine invariant that is now violated

Fix the condition that caused the assertion to fail
-- Investigate and correct the data or logic that violated the invariant

Why this works

Address the root cause rather than removing or disabling the assertion

Fix 2

Disable assertions for production if they are development-only checks

WHEN Assertions are not appropriate for production workloads

Disable assertions for production if they are development-only checks
-- In postgresql.conf:
-- plpgsql.check_asserts = off

Why this works

Setting plpgsql.check_asserts=off disables all ASSERT checks without removing them from code

What not to do

✕ Do not remove ASSERT statements to fix the error without investigating why the assertion failed

Assertions exist to catch bugs; removing them hides the underlying problem

Version notes
9.5

ASSERT statement added in PostgreSQL 9.5

Sources
Official documentation ↗

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

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