P0001
PostgreSQLERRORNotablePL/pgSQL ErrorHIGH confidence

raise_exception

What this means

A PL/pgSQL function executed a RAISE EXCEPTION statement. This is the standard mechanism for signalling application-level errors from stored procedures and functions.

Why it happens
  1. 1PL/pgSQL RAISE EXCEPTION reached in a function or procedure
  2. 2Business rule validation failed and the function deliberately raised an exception
  3. 3Trigger function rejected an operation via RAISE EXCEPTION
How to reproduce

Any PL/pgSQL function, procedure, or trigger that calls RAISE EXCEPTION

trigger — this will error
trigger — this will error
CREATE OR REPLACE FUNCTION check_age(age int) RETURNS void AS $
BEGIN
  IF age < 18 THEN
    RAISE EXCEPTION 'Age must be 18 or older, got: %', age;
  END IF;
END;
$ LANGUAGE plpgsql;

SELECT check_age(15);

expected output

ERROR:  P0001: Age must be 18 or older, got: 15

Fix 1

Satisfy the business rule that triggered the exception

WHEN Input data failed a validation check

Satisfy the business rule that triggered the exception
SELECT check_age(21);  -- provide valid input

Why this works

Pass data that satisfies the condition checked in the PL/pgSQL function

Fix 2

Catch the exception in the calling code

WHEN The exception is expected for some inputs

Catch the exception in the calling code
BEGIN;
  BEGIN
    PERFORM check_age(15);
  EXCEPTION WHEN raise_exception THEN
    RAISE NOTICE 'Caught expected error: %', SQLERRM;
  END;
COMMIT;

Why this works

Handle P0001 in an EXCEPTION block to implement graceful fallback

What not to do

✕ Do not swallow P0001 exceptions silently without logging

Business rule violations are important signals; silent catch-and-ignore hides bugs

Sources

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