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  1. MariaDB Server
  2. MDEV-26723

Cached stored procedures are counted as global memory, should be session memory

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    Description

      When stored procedure is cached, the bytes are counted towards global memory, which can be
      retrieved with 

      select variable_value  from information_schema.global_status where variable_name='MEMORY_USED';

      This is wrong, as the caches are per-session (THD::sp_proc_cache etc). Thus populating cache should result in increase of "information_schema.session_status where variable_name='MEMORY_USED'" instead, which is not happening

      Commands below create and execute a dummy stored procedure, and measure increase of global and session memory for that operation.

      session memory increases by 96 bytes , global memory by some 10K . Session memory increase only happens first time around, i.e if you create another procedure, and execute it, session memory will increase by 0 bytes, but global memory by some 12K. (Those numbers are taken from current debug 10.3 on my box.

      mysql>  select variable_value into @global_mem_used from information_schema.global_status where variable_name='MEMORY_USED';
      		 
      Query OK, 1 row affected (0.00 sec)
      		 
       
      		 
      mysql>  select variable_value into @local_mem_used from information_schema.session_status where variable_name='MEMORY_USED';
      		 
      Query OK, 1 row affected (0.00 sec)
      		 
       
      		 
      mysql>  create procedure sp1() BEGIN END;
      		 
      Query OK, 0 rows affected (0.01 sec)
      		 
       
      		 
      mysql> call sp1();
      		 
      Query OK, 0 rows affected (0.00 sec)
      		 
       
      		 
      mysql>  select variable_value-@global_mem_used as global_mem_diff from information_schema.global_status where variable_name='MEMORY_USED';
      		 
      +-----------------+
      		 
      | global_mem_diff |
      		 
      +-----------------+
      		 
      |           10888 |
      		 
      +-----------------+
      		 
      1 row in set (0.00 sec)
      		 
       
      		 
      mysql>  select variable_value-@local_mem_used as local_mem_diff from information_schema.session_status where variable_name='MEMORY_USED';
      		 
      +----------------+
      		 
      | local_mem_diff |
      		 
      +----------------+
      		 
      |             96 |
      		 
      +----------------+
      		 
      1 row in set (0.00 sec)

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          relates to

          Bug - A problem which impairs or prevents the functions of the product. MDEV-26754 main.sp test fails for embedded server

          • Major - Major loss of function.
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              shulga Dmitry Shulga
              wlad Vladislav Vaintroub
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                Updated:

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