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MDEV-20699 mysqldump of routines causes MariaDB to get killed by oom-killer

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The reason for this behavior is that SP get cached, per connection.
The stored_program_cache is size of this cache, which amounts to 256
routines by default. A compiled stored procedure can easily be several
megabytes in size. Thus calling SHOW CREATE PROCEDURE for all stored
procedures, like mysqldump does, can require significant amount of memory.

Fixed by bypassing the cache for "SHOW CREATE". This should normally be
fine also perfomance-wise, as cache is meant to be used for repeated
execution, not repeated SHOW CREATEs.

Added a test to verify that CREATE PROCEDURE + SHOW CREATE PROCEURE do not
cache, i.e amount of allocated memory does not change.

Note, there is a change in existing behavior in an edge case :
If "SHOW CREATE PROCEDURE p1" called from p1, after p1 was altered, now
this will now return altered code. Previour behavior - relied on caching
and would return old code. The previous behavior might was not necessarily
correct.
This commit is contained in:
Vladislav Vaintroub
2021-09-27 17:43:36 +02:00
parent d7aa81c862
commit 1f099418b6
6 changed files with 49 additions and 21 deletions
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4
mysql-test/main/sp-bugs.result
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@ -182,7 +182,7 @@ RETURN 0;
END latin1 latin1_swedish_ci latin1_swedish_ci
SHOW CREATE FUNCTION TESTF_bug11763507;
Function sql_mode Create Function character_set_client collation_connection Database Collation
testf_bug11763507 CREATE DEFINER=`root`@`localhost` FUNCTION `testf_bug11763507`() RETURNS int(11)
TESTF_bug11763507 CREATE DEFINER=`root`@`localhost` FUNCTION `TESTF_bug11763507`() RETURNS int(11)
BEGIN
RETURN 0;
END latin1 latin1_swedish_ci latin1_swedish_ci
@ -212,7 +212,7 @@ SELECT "PROCEDURE testp_bug11763507";
END latin1 latin1_swedish_ci latin1_swedish_ci
SHOW CREATE PROCEDURE TESTP_bug11763507;
Procedure sql_mode Create Procedure character_set_client collation_connection Database Collation
testp_bug11763507 CREATE DEFINER=`root`@`localhost` PROCEDURE `testp_bug11763507`()
TESTP_bug11763507 CREATE DEFINER=`root`@`localhost` PROCEDURE `TESTP_bug11763507`()
BEGIN
SELECT "PROCEDURE testp_bug11763507";
END latin1 latin1_swedish_ci latin1_swedish_ci