Details
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Bug
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Status: In Review (View Workflow)
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Major
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Resolution: Unresolved
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11.4
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None
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None
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Can result in unexpected behaviour
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Q2/2026 Server Maintenance
Description
This bug is masked by MDEV-39207 and caused by the 11.1+ change MDEV-31746.
The MDEV-31746 patch changed the hash key calculation in session sysvar tracker from the sys_var pointer to its offset. This was useful for non-plugin variable aliases, but not so much for plugin variables which all have offset 0.
The bug is masked by MDEV-39207 because all plugin session vars are marked with "*test_loaded=false". If none of the plugin session vars are marked loaded, then false positive deduplication does not surface.
With the current MDEV-39207 patch applied to 11.4, the bug becomes apparent:
sys_vars.session_track_system_variables_basic [ fail ]
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Test ended at 2026-03-31 16:42:51
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CURRENT_TEST: sys_vars.session_track_system_variables_basic
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--- /home/ycp/source/mariadb-server/11.4/src/mysql-test/suite/sys_vars/r/session_track_system_variables_basic.result 2026-03-31 16:42:21.710652757 +1100
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+++ /home/ycp/source/mariadb-server/11.4/src/mysql-test/suite/sys_vars/r/session_track_system_variables_basic.reject 2026-03-31 16:42:51.418448445 +1100
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@@ -168,20 +168,17 @@
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set global session_track_system_variables='myisam_sort_buffer_size,example_int_var';
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select @@global.session_track_system_variables;
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@@global.session_track_system_variables
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-example_int_var,myisam_sort_buffer_size
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+myisam_sort_buffer_size
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set global session_track_system_variables='myisam_block_size,myisam_sort_buffer_size,character_set_client,example_int_var';
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select @@global.session_track_system_variables;
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@@global.session_track_system_variables
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-character_set_client,example_int_var,myisam_sort_buffer_size
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+character_set_client
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# Session tracking works as expected for plugin session var
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connect foo,localhost,root;
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select @@session.session_track_system_variables;
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@@session.session_track_system_variables
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-character_set_client,example_int_var,myisam_sort_buffer_size
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+character_set_client
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set session example_int_var = -1;
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--- Tracker : SESSION_TRACK_SYSTEM_VARIABLES
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--- example_int_var: -1
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-
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connection default;
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disconnect foo;
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uninstall soname 'ha_example.so'; |
In the first diff hunk, example_int_var and myisam_sort_buffer_size are both plugin session vars, so they are incorrectly deemed duplicates for having the same 0 offset and only one appears.
In the second diff hunk, example_int_var and myisam_sort_buffer_size are deemed duplicates of myisam_block_size for the same reason. But myisam_block_size does not appear either because it is a global plugin var, and global plugin vars have *test_load==static_unloaded.
Attachments
Issue Links
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