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  1. MariaDB Server
  2. MDEV-21782

lower_case_table_names system variable's usage message needs several fixes

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Details

    • Bug
    • Status: Open (View Workflow)
    • Major
    • Resolution: Unresolved
    • 10.1.44, 10.2.31, 10.3.22, 10.4.12
    • 10.4(EOL)
    • Variables
    • None

    Description

      The lower_case_table_names system variable supports the values 0, 1, and 2. We can tell from the source code:

      static Sys_var_uint Sys_lower_case_table_names(
             "lower_case_table_names",
             "If set to 1 table names are stored in lowercase on disk and table "
             "names will be case-insensitive.  Should be set to 2 if you are using "
             "a case insensitive file system",
             READ_ONLY GLOBAL_VAR(lower_case_table_names),
             CMD_LINE(OPT_ARG, OPT_LOWER_CASE_TABLE_NAMES),
             VALID_RANGE(0, 2),
      #ifdef FN_NO_CASE_SENSE
          DEFAULT(1),
      #else
          DEFAULT(0),
      #endif
             BLOCK_SIZE(1));
      

      https://github.com/MariaDB/server/blob/mariadb-10.4.12/sql/sys_vars.cc#L1462

      We can see that the usage message only mentions the values 1 and 2:

      MariaDB [(none)]> SELECT VARIABLE_COMMENT FROM information_schema.SYSTEM_VARIABLES WHERE VARIABLE_NAME='lower_case_table_names';
      +-----------------------------------------------------------------------------------------------------------------------------------------------------------------------+
      | VARIABLE_COMMENT                                                                                                                                                      |
      +-----------------------------------------------------------------------------------------------------------------------------------------------------------------------+
      | If set to 1 table names are stored in lowercase on disk and table names will be case-insensitive.  Should be set to 2 if you are using a case insensitive file system |
      +-----------------------------------------------------------------------------------------------------------------------------------------------------------------------+
      1 row in set (0.002 sec)
      

      The message should also mention the value 0, and it should mention why that value would be used.

      The message should also explain more about what the value 2 does. It currently explains absolutely nothing about it, other than "you should use it." On another strange note, why does the usage message make this claim?:

      Should be set to 2 if you are using a case insensitive file system

      That doesn't make sense when you look at the code. If you have a case-insensitive file system, then it defaults to 1:

      #ifdef FN_NO_CASE_SENSE
          DEFAULT(1),
      

      Why is the code ignoring its own recommendation?

      It appears that this usage message needs several fixes.

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              greenman Ian Gilfillan
              GeoffMontee Geoff Montee (Inactive)
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              Dates

                Created:
                Updated:

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