SQLSTATE 39P01 ERROR Class 39: External Routine Invocation Exception

trigger_protocol_violated Trigger Protocol Violated — SQLSTATE 39P01

SQLSTATE 39P01 (trigger_protocol_violated): An external routine invocation failed.

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Last reviewed May 2025 Grounded in source

Symptoms

The server reports SQLSTATE 39P01 (trigger_protocol_violated), a condition in the External Routine Invocation Exception class.

  • The error is written to the server log and returned to the client carrying SQLSTATE 39P01.
  • Any driver (libpq, JDBC, psycopg, npgsql, pgx) surfaces this code in its error object so you can branch on it programmatically.
  • PL/pgSQL can trap it by name: EXCEPTION WHEN trigger_protocol_violated THEN.

Environment

Severity: ERROR  |  PostgreSQL versions: 12, 13, 14, 15, 16, 17

Reproduce with the exact statement and read the full message in the server log (raise log_min_messages / set log_min_error_statement for more context).

Root Cause

39P01 belongs to Class 39 — External Routine Invocation Exception. In this class, an external routine invocation failed.

The first two characters (39) identify the error class, so application code can match the whole class via 39000 when the specific code is not needed.

Diagnostic Queries

Recovery

Verify argument types and the extension version; review the routine's expectations.

Reference: PostgreSQL error codes — Class 39 (External Routine Invocation Exception).

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