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Description

The 'program limit exceeded' error (SQLSTATE 54000) in PostgreSQL indicates that a database operation or the system itself has hit an internal configuration or resource limit. This typically occurs when a process attempts to consume more resources than allowed by the server's settings or the underlying operating system.

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Error Message

program limit exceeded

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Known Causes

4 known causes

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Excessive Database Connections

The number of active connections to the PostgreSQL server has reached or exceeded the configured `max_connections` limit.

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Complex Query Resource Usage

A single query or transaction is attempting to consume more memory or temporary disk space than allowed by parameters like `work_mem` or `temp_buffers`.

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Operating System Resource Constraints

The underlying operating system has imposed limits on resources (e.g., open files, process memory) that a PostgreSQL process or the entire instance is attempting to exceed.

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PostgreSQL Configuration Limits

Other internal PostgreSQL parameters, such as `max_locks_per_transaction` or `max_prepared_transactions`, have been exceeded by current operations.

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Solutions

3 solutions available

1. Increase `max_stack_depth` for Complex Queries medium

Adjust the maximum stack depth allowed for queries that are too complex.

1

Identify the query causing the 'Program Limit Exceeded' error. This often happens with deeply nested subqueries, complex CTEs, or recursive queries.

2

Temporarily increase the `max_stack_depth` parameter. This parameter controls the maximum recursion depth for expressions. A higher value allows for more complex query structures.

ALTER SYSTEM SET max_stack_depth = '2MB'; -- Or a higher value like '4MB', '8MB' depending on your system and query complexity
SELECT pg_reload_conf();

3

Restart the PostgreSQL server for the change to take full effect, though `pg_reload_conf()` often suffices for this parameter.

sudo systemctl restart postgresql

4

Re-run the problematic query. If it succeeds, you've found a workaround. For a permanent solution, consider refactoring the query to be less complex.

2. Refactor Complex Queries advanced

Simplify overly complex SQL queries that might be hitting internal recursion or execution limits.

1

Analyze the query that triggers the error. Look for deeply nested subqueries, excessive use of Common Table Expressions (CTEs), or complex recursive queries.

2

Break down the complex query into smaller, more manageable parts. This can involve creating temporary tables or using intermediate CTEs that are processed sequentially.

Example: Instead of a single complex query, consider:
CREATE TEMP TABLE intermediate_results AS SELECT ... FROM ... WHERE ...;
SELECT ... FROM intermediate_results JOIN ... ON ...;

3

If using recursive CTEs, ensure the recursion base case is correctly defined and the recursive step doesn't lead to an infinite loop or excessively deep recursion. Consider adding a depth limit to the recursion.

WITH RECURSIVE my_cte AS (
    SELECT ...
    FROM ...
    WHERE ...
    UNION ALL
    SELECT ...
    FROM my_cte
    WHERE ... -- Add a condition to limit recursion depth if possible
)
SELECT * FROM my_cte;

4

Consider alternative SQL constructs or approaches. For example, if you're performing complex aggregations, see if they can be simplified or achieved with window functions more efficiently.

3. Increase System Stack Size (OS Level) medium

Adjust the operating system's stack size limit if PostgreSQL's stack usage exceeds it.

1

Determine if the 'Program Limit Exceeded' error is due to the operating system's stack size limit rather than PostgreSQL's internal limits. This is less common but possible.

2

For Linux systems, you can increase the stack limit using the `ulimit` command. This can be done temporarily in the current shell or permanently by modifying system configuration files.

# Temporarily increase stack size in the current shell (e.g., to 8MB)
ulimit -s 8192
# To make it permanent, edit /etc/security/limits.conf and add lines like:
# * soft stack 8192
# * hard stack 16384
# Then, restart your session or reboot.

3

If PostgreSQL is running as a service, you might need to configure the service to inherit the increased limits or specify them in the service startup script. For systemd, you can often set `LimitStack` in the service unit file.

Example for systemd service unit file (/etc/systemd/system/postgresql.service):
[Service]
LimitStack=8M

4

Restart the PostgreSQL service after making OS-level changes.

sudo systemctl restart postgresql

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Related Errors

5 related errors

PostgreSQL Error 54000: Program Limit Exceeded