statement_too_complex stack depth limit exceeded — 54001

Symptoms

Server-side recursion went deeper than max_stack_depth allows — typically deeply nested function calls or runaway recursive SQL/PL/pgSQL. PostgreSQL raises SQLSTATE 54001 (statement_too_complex).

• A HINT suggests increasing max_stack_depth if safe.
• Often from infinite or very deep recursion.
• Guards against crashing the backend via stack overflow.

What the server log shows

ERROR:  stack depth limit exceeded
HINT:  Increase the configuration parameter max_stack_depth (currently 2048kB), after ensuring the platform's stack depth limit is adequate.

Why PostgreSQL raises this — what the manual says

Section 19.4.1 Memory (max_stack_depth):

“Specifies the maximum safe depth of the server’s execution stack.”

PostgreSQL checks execution stack depth against max_stack_depth. When recursion or nesting exceeds it, the statement is aborted with 54001 rather than risking a stack overflow that would crash the backend.

Common causes

• Infinite or unbounded recursion in a function or recursive CTE.
• Very deeply nested function/trigger calls.
• A recursive query missing a proper termination condition.

Relevant GUC parameters

How to fix it

1. Add a termination/base case to recursive functions or CTEs.
2. Refactor deep recursion into iteration.
3. If legitimately deep, raise max_stack_depth — but keep it below the OS ulimit -s.

Related & next steps

• SQLSTATE 54001 — Statement Too Complex (full reference)
• Message: target lists can have at most N entries
• Glossary: Recursion

Reference: PostgreSQL 18 Section 20.4 “Resource Consumption”.