[#MDEV-30631] System variables metadata shouldn't show values of INNODB_COMPRESSION

The INFORMATION_SCHEMA.SYSTEM_VARIABLES table contains a misleading ENUM_VALUE_LIST for INNODB_COMPRESSION_ALGORITHM. It lists algorithms that are (in principle) supported by MariaDB but (in reality) not compiled into this build.

Here is an example on Amazon RDS MariaDB 10.6.11, which is built to support zlib, lzma, and none, but not other compression algorithms:

System variable metadata says that any of the following values are supported: none,zlib,lz4,lzo,lzma,bzip2,snappy

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Server version: 10.6.11-MariaDB-log managed by https://aws.amazon.com/rds/

Copyright (c) 2000, 2018, Oracle, MariaDB Corporation Ab and others.

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MariaDB [(none)]> select * from information_schema.system_variables where variable_name='INNODB_COMPRESSION_ALGORITHM'\G

*************************** 1. row ***************************

        VARIABLE_NAME: INNODB_COMPRESSION_ALGORITHM

        SESSION_VALUE: NULL

         GLOBAL_VALUE: zlib

  GLOBAL_VALUE_ORIGIN: COMPILE-TIME

        DEFAULT_VALUE: zlib

       VARIABLE_SCOPE: GLOBAL

        VARIABLE_TYPE: ENUM

     VARIABLE_COMMENT: Compression algorithm used on page compression. One of: none, zlib, lz4, lzo, lzma, bzip2, or snappy

    NUMERIC_MIN_VALUE: NULL

    NUMERIC_MAX_VALUE: NULL

   NUMERIC_BLOCK_SIZE: NULL

      ENUM_VALUE_LIST: none,zlib,lz4,lzo,lzma,bzip2,snappy

            READ_ONLY: NO

COMMAND_LINE_ARGUMENT: OPTIONAL

    GLOBAL_VALUE_PATH: NULL

1 row in set (0.002 sec)

MariaDB [(none)]> set global innodb_compression_algorithm=bzip2;

ERROR 1231 (42000): Variable 'innodb_compression_algorithm' can't be set to the value of 'bzip2'

MariaDB [(none)]> set global innodb_compression_algorithm=lzma;

Query OK, 0 rows affected (0.000 sec)

MariaDB [(none)]> set global innodb_compression_algorithm=zlib;

Query OK, 0 rows affected (0.000 sec)

MariaDB [(none)]> set global innodb_compression_algorithm=none;

Query OK, 0 rows affected (0.000 sec)

Problem: The list of "allowed values" are not all allowed. In order to determine the actually allowed values, you have to test them one by one, and see which ones don't error out.

Solution: The code to populate the information_schema metadata tables/views should be updated to list only the allowed values that can actually be set.

[MDEV-30631] System variables metadata shouldn't show values of INNODB_COMPRESSION_ALGORITHM that can't be set Created: 2023-02-10 Updated: 2023-06-08 Resolved: 2023-04-01
Status:	Closed
Project:	MariaDB Server
Component/s:	None
Affects Version/s:	10.6
Fix Version/s:	N/A

[MDEV-30631] System variables metadata shouldn't show values of INNODB_COMPRESSION_ALGORITHM that can't be set Created: 2023-02-10 Updated: 2023-06-08 Resolved: 2023-04-01