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MDEV-9959: A serious MariaDB server performance bug

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If a derived table has SELECT DISTINCT, provide index statistics for it so that the join optimizer in the
upper select knows that ref access to the table will produce one row.
This commit is contained in:
Varun Gupta
2019-04-30 21:05:50 +05:30
parent 8c8bee0a56
commit cb9fa1a08b
10 changed files with 153 additions and 7 deletions
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sql/sql_class.cc
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@ -847,6 +847,7 @@ THD::THD(my_thread_id id, bool is_wsrep_applier, bool skip_global_sys_var_lock)
invoker.init();
prepare_derived_at_open= FALSE;
create_tmp_table_for_derived= FALSE;
force_read_stats= FALSE;
save_prep_leaf_list= FALSE;
org_charset= 0;
/* Restore THR_THD */