statement_too_complex stack depth limit exceeded — 54001

Symptoms

Execution exceeded the stack depth limit, usually from deeply nested expressions or unbounded recursion. PostgreSQL raises SQLSTATE 54001 (statement_too_complex).

• The stack depth limit was hit during execution.
• Common with infinite/very deep recursion in functions.
• Also from extremely nested expressions.

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 guards against stack overflow by capping execution depth at max_stack_depth. Deep recursion (e.g. a runaway recursive function or CTE) or extreme expression nesting exceeds it, so PostgreSQL reports 54001 to avoid a crash.

Common causes

• Infinite or excessively deep recursion in a function/CTE.
• Extremely nested expressions or views.
• max_stack_depth set lower than the kernel allows.

Relevant GUC parameters

How to fix it

1. Fix the recursion (add a termination condition / depth limit).
2. Reduce expression nesting or refactor the query.
3. Raise max_stack_depth only after increasing the OS stack limit (ulimit -s).

Related & next steps

• SQLSTATE 54001 — Statement Too Complex (full reference)
• Message: tables can have at most 1600 columns
• Glossary: Recursive CTE

Reference: PostgreSQL 18 Section 20.4 “Resource Consumption”.