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Description

This error indicates that a stored procedure has called itself recursively too many times, exceeding the `max_sp_recursion_depth` server variable. It typically occurs when a recursive stored procedure enters an infinite loop or has a very deep call stack.

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Error Message

Recursive limit %d (as set by the max_sp_recursion_depth variable) was exceeded for routine %s

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Known Causes

4 known causes

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Infinite Loop in Procedure

A bug in the stored procedure logic causes it to call itself endlessly without a proper termination condition.

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Deep Recursive Logic

The intended recursive logic of the stored procedure is genuinely very deep, exceeding the default recursion limit.

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Insufficient Recursion Depth

The `max_sp_recursion_depth` server variable is set too low for the complexity of the recursive operation.

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Unintentional Self-Call

The stored procedure inadvertently calls itself or another procedure that leads back to itself, forming an unexpected recursive loop.

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Solutions

3 solutions available

1. Temporarily Increase `max_sp_recursion_depth` easy

Increase the maximum allowed recursion depth for stored procedures for immediate relief.

1

Connect to your MySQL server as a user with sufficient privileges (e.g., root).

2

Check the current value of `max_sp_recursion_depth`.

SHOW VARIABLES LIKE 'max_sp_recursion_depth';

3

Increase the `max_sp_recursion_depth` variable. A common increase is to 20 or 30, but you may need to experiment based on your specific stored procedure.

SET GLOBAL max_sp_recursion_depth = 30;

4

If you want this change to persist across server restarts, you need to update your MySQL configuration file (my.cnf or my.ini). Locate the `[mysqld]` section and add or modify the `max_sp_recursion_depth` line.

[mysqld]
max_sp_recursion_depth = 30

5

Restart your MySQL server for the configuration file changes to take effect.

2. Refactor Recursive Stored Procedure advanced

Rewrite the stored procedure to eliminate or reduce its reliance on recursion.

1

Analyze the stored procedure that is causing the recursion limit to be exceeded. Identify the recursive calls and the logic behind them.

2

Consider an iterative approach using loops (WHILE, REPEAT, LOOP) instead of recursion. This is often more efficient and avoids recursion depth limits.

Example of replacing recursion with a loop (conceptual):

-- Original Recursive Logic (simplified):
-- DELIMITER $$
-- CREATE PROCEDURE recursive_example(level INT) 
-- BEGIN
--   IF level > 0 THEN
--     -- do something
--     CALL recursive_example(level - 1);
--   END IF;
-- END $$

-- Iterative Approach:
DELIMITER $$
CREATE PROCEDURE iterative_example(start_level INT)
BEGIN
  DECLARE current_level INT DEFAULT start_level;
  WHILE current_level > 0 DO
    -- do something
    SET current_level = current_level - 1;
  END WHILE;
END $$
DELIMITER ;

3

If recursion is essential, try to break down the problem into smaller, non-recursive sub-problems that can be solved sequentially.

4

Optimize the recursive calls by passing fewer parameters or by ensuring that the recursive step always makes progress towards the base case.

5

Thoroughly test the refactored procedure to ensure it produces the correct results and performs efficiently.

3. Review and Optimize Data Structure and Query medium

Examine the underlying data and queries that trigger deep recursion to identify inefficiencies.

1

Understand why the stored procedure is making so many recursive calls. Is it processing a very large or deeply nested data structure?

2

Examine the data itself. Are there unintended cycles or extremely deep hierarchies in your data that are causing the recursion?

3

If possible, denormalize or restructure your data to reduce the depth of relationships that require recursive traversal.

4

Optimize the queries within the stored procedure. Ensure that they are using appropriate indexes and are not performing unnecessary operations that lead to repeated recursive calls.

5

Consider using Common Table Expressions (CTEs) with recursive capabilities in newer MySQL versions (8.0+) as an alternative to stored procedure recursion, which might offer better performance and readability.

Example of a recursive CTE:

WITH RECURSIVE cte_name (column1, column2, ...) AS (
  -- Anchor member
  SELECT ...
  FROM your_table
  WHERE ...
  UNION ALL
  -- Recursive member
  SELECT t.column1, t.column2, ...
  FROM your_table t
  JOIN cte_name ON t.parent_id = cte_name.id
  WHERE ...
)
SELECT * FROM cte_name;

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Related Errors

5 related errors

MySQL Error 1456: Stored Procedure Recursion Limit Exceeded