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  1. MariaDB Server
  2. MDEV-40270

@@default_master_connection does not convert character sets

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Details

    • Unexpected results
    • Q3/2026 Replic. Maintenance, Q3/2026 Replic. Development

    Description

      GBK encoding

      		 
      SET NAMES GBK;
      		 
       
      		 
      SET       @@SESSION.default_master_connection= 'Latin';
      		 
      SELECT    @@SESSION.default_master_connection , #=> Latin
      		 
        CHARSET(@@SESSION.default_master_connection); #=> utf8mb3
      		 
       
      		 
      SET       @@SESSION.default_master_connection= '汉字';
      		 
      SELECT    @@SESSION.default_master_connection , #=> ????
      		 
        CHARSET(@@SESSION.default_master_connection); #=> utf8mb3
      		 
       
      		 
      SET       @@GLOBAL.init_slave= '汉字'; # not bugged
      		 
      SELECT    @@GLOBAL.init_slave , #=> 汉字
      		 
        CHARSET(@@GLOBAL.init_slave); #=> utf8mb3
      		 
      SET @@GLOBAL.init_slave= DEFAULT;
      		 
       
      		 
      SET       @mystr= '汉字'; # not affected
      		 
      SELECT    @mystr , #=> 汉字
      		 
        CHARSET(@mystr); #=> gbk

      Analysis

      Item::val_str() doesn't specify the collation of the returned string.
      For example, Item_string::val_str() returns the string behind this item, thus using the collation of the item.

      However, Sys_var_session_lexstring::do_check() does not realize this detail and expects the string to be in the @@character_set_system collation.

      Sys_var_session_lexstring has been merged away in 11.3 (Commit 6151bde48c); its only instance was @@default_master_connection.

      [P.S.]
      @@debug_sync has the same mistake and has not been merged away.
      @@debug_dbug is not bugged.

      Attachments

        Issue Links

          blocks

          Bug - A problem which impairs or prevents the functions of the product. MDEV-40295 No warning when string system variables fail to convert character sets

          • Minor - Minor loss of function, or other problem where easy workaround is present.
          • Open
          causes

          Bug - A problem which impairs or prevents the functions of the product. MDEV-39757 use-of-uninitialized-value in skip_trailing_space

          • Critical - Crashes, loss of data, severe memory leak.
          • Closed

          Bug - A problem which impairs or prevents the functions of the product. MDEV-39759 use-of-uninitialized-value in bcmp

          • Critical - Crashes, loss of data, severe memory leak.
          • Closed
          relates to

          Bug - A problem which impairs or prevents the functions of the product. MDEV-40271 @@default_master_connection is corrupted if set to a string with null bytes

          • Critical - Crashes, loss of data, severe memory leak.
          • Needs Feedback
          split from

          Bug - A problem which impairs or prevents the functions of the product. MDEV-39757 use-of-uninitialized-value in skip_trailing_space

          • Critical - Crashes, loss of data, severe memory leak.
          • Closed
          split to

          Bug - A problem which impairs or prevents the functions of the product. MDEV-40295 No warning when string system variables fail to convert character sets

          • Minor - Minor loss of function, or other problem where easy workaround is present.
          • Open

          Activity

            People

              Elkin Andrei Elkin
              ParadoxV5 Jimmy Hú
              Jimmy Hú Jimmy Hú
              Andrei Elkin Andrei Elkin
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                Updated:

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