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  1. MariaDB Server
  2. MDEV-23492

performance_schema_digests_size changing from default to 5000 when enabling performance_schema

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      Description

      Hi Team,

      On MariaDB version 10.3.13, default value of performance_schema_digests_size is '-1' as per document. However when enabling performance_schema on this the value is getting changed from -1 to 5000

      https://mariadb.com/kb/en/performance-schema-system-variables/#performance_schema_digests_size

      I did not find any document stating the same. Steps to reproduce

      1. Installed MariaDB 10.3.13 on rhel 7 and verify the value of 'performance_schema_digests_size' it will show '-1'.
      2. Enable performance_scheme and again see the value, it changes to '5000'
      3. Though I can change value between -1 to 200 but not able to understand howcome it is showing 5000 where as the limit is between -1 to 200.

      [root@ip-xx.xx.xx.xx ~]# mysql
      Welcome to the MariaDB monitor.  Commands end with ; or \g.
      Your MariaDB connection id is 9
      Server version: 10.3.13-MariaDB MariaDB Server
       
      Copyright (c) 2000, 2018, Oracle, MariaDB Corporation Ab and others.
       
      Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.
       
      MariaDB [(none)]> select @@version; select @@performance_schema_digests_size;select @@performance_schema;
      +-----------------+
      | @@version       |
      +-----------------+
      | 10.3.13-MariaDB |
      +-----------------+
      1 row in set (0.000 sec)
       
      +-----------------------------------+
      | @@performance_schema_digests_size |
      +-----------------------------------+
      |                                -1 |
      +-----------------------------------+
      1 row in set (0.000 sec)
       
      +----------------------+
      | @@performance_schema |
      +----------------------+
      |                    0 |
      +----------------------+
      1 row in set (0.000 sec)
       
      MariaDB [(none)]>
       
      After enabling performacne_schema on EC2 instance the value changed to 5000
       
      [root@ip-xx.xx.xx.xx my.cnf.d]# mysql
      Welcome to the MariaDB monitor.  Commands end with ; or \g.
      Your MariaDB connection id is 8
      Server version: 10.3.13-MariaDB MariaDB Server
       
      Copyright (c) 2000, 2018, Oracle, MariaDB Corporation Ab and others.
       
      Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.
       
      MariaDB [(none)]> select @@version; select @@performance_schema_digests_size;select @@performance_schema;
      +-----------------+
      | @@version       |
      +-----------------+
      | 10.3.13-MariaDB |
      +-----------------+
      1 row in set (0.000 sec)
       
      +-----------------------------------+
      | @@performance_schema_digests_size |
      +-----------------------------------+
      |                              5000 |
      +-----------------------------------+
      1 row in set (0.000 sec)
       
      +----------------------+
      | @@performance_schema |
      +----------------------+
      |                    1 |
      +----------------------+
      1 row in set (0.000 sec)
       
      MariaDB [(none)]>
       
      Tried chaning performance_schema_digests_size to 100 and was able to change.
      [root@ip-xx.xx.xx.xx my.cnf.d]# mysql
      Welcome to the MariaDB monitor.  Commands end with ; or \g.
      Your MariaDB connection id is 8
      Server version: 10.3.13-MariaDB MariaDB Server
       
      Copyright (c) 2000, 2018, Oracle, MariaDB Corporation Ab and others.
       
      Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.
       
      MariaDB [(none)]> select @@version; select @@performance_schema_digests_size;select @@performance_schema;
      +-----------------+
      | @@version       |
      +-----------------+
      | 10.3.13-MariaDB |
      +-----------------+
      1 row in set (0.000 sec)
       
      +-----------------------------------+
      | @@performance_schema_digests_size |
      +-----------------------------------+
      |                               100 |
      +-----------------------------------+
      1 row in set (0.000 sec)
       
      +----------------------+
      | @@performance_schema |
      +----------------------+
      |                    1 |
      +----------------------+
      1 row in set (0.000 sec)
       
      MariaDB [(none)]>
      

      Again changed value from 100 to -1 when performance schema is enabled and it changed to 5000

      [root@ip-xx.xx.xx.xx my.cnf.d]# mysql
      Welcome to the MariaDB monitor.  Commands end with ; or \g.
      Your MariaDB connection id is 8
      Server version: 10.3.13-MariaDB MariaDB Server
       
      Copyright (c) 2000, 2018, Oracle, MariaDB Corporation Ab and others.
       
      Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.
       
      MariaDB [(none)]> select @@version; select @@performance_schema_digests_size;select @@performance_schema;
      +-----------------+
      | @@version       |
      +-----------------+
      | 10.3.13-MariaDB |
      +-----------------+
      1 row in set (0.000 sec)
       
      +-----------------------------------+
      | @@performance_schema_digests_size |
      +-----------------------------------+
      |                              5000 |
      +-----------------------------------+
      1 row in set (0.000 sec)
       
      +----------------------+
      | @@performance_schema |
      +----------------------+
      |                    1 |
      +----------------------+
      1 row in set (0.000 sec)
       
      MariaDB [(none)]>
      

      Is this expected behavior?

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            Assignee:
            serg Sergei Golubchik
            Reporter:
            jksing Jitender Singh
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              Updated:
              Resolved:

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