Details
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Bug
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Status: Closed (View Workflow)
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Major
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Resolution: Fixed
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10.0, 10.1, 10.2, 10.3, 10.4
Description
The problem is repeatable starting from 10.0 with help of the Memory_used status variable, but the excessive memory consumption probably also takes place in 5.5 (which does not have Memory_used).
This script:
DROP PROCEDURE IF EXISTS p1; |
DELIMITER $$
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CREATE PROCEDURE p1() |
BEGIN
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DECLARE i INT DEFAULT 1; |
WHILE i <= 500000
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DO
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BEGIN |
DECLARE cur CURSOR FOR SELECT 1 FROM DUAL; |
IF (i % 100000 = 0) THEN |
SHOW STATUS LIKE 'Memory_used'; |
END IF; |
END; |
SET i=i+1; |
END WHILE; |
END; |
$$
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DELIMITER ;
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CALL p1;
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produced the following output:
+---------------+---------+
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| Variable_name | Value |
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+---------------+---------+
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| Memory_used | 7391264 |
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+---------------+---------+
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1 row in set (2.09 sec)
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|
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+---------------+----------+
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| Variable_name | Value |
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+---------------+----------+
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| Memory_used | 14459048 |
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+---------------+----------+
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1 row in set (4.19 sec)
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|
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+---------------+----------+
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| Variable_name | Value |
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+---------------+----------+
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| Memory_used | 21746936 |
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+---------------+----------+
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1 row in set (6.21 sec)
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|
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+---------------+----------+
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| Variable_name | Value |
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+---------------+----------+
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| Memory_used | 29132648 |
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+---------------+----------+
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1 row in set (8.24 sec)
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|
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+---------------+----------+
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| Variable_name | Value |
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+---------------+----------+
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| Memory_used | 36045544 |
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+---------------+----------+
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1 row in set (10.25 sec)
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The thread leaks some memory at every loop iteration.
If I now comment out the line with cursor:
-- DECLARE cur CURSOR FOR SELECT 1 FROM DUAL; |
and rerun the script, the amount of thread memory reported permanently stays near 64K and does not grow through iterations.
The problem resides in this code:
bool sp_rcontext::push_cursor(THD *thd, sp_lex_keeper *lex_keeper) |
{
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/* |
We should create cursors in the callers arena, as
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it could be (and usually is) used in several instructions.
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*/
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sp_cursor *c= new (callers_arena->mem_root) sp_cursor(thd, lex_keeper); |
...
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}
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At the the push_cursor() call time, callers_area points to THD::main_mem_root, which is freed only after the SP instructions loop.
Cursors should be created at some different memory root.
Attachments
Issue Links
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- Closed
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