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b5299f3559
SLOW/CRASHES SEMAPHORE Problem: There are 2 lakh tables - fk_000001, fk_000002 ... fk_200000. All of them are related to the same parent_table through a foreign key constraint. When the parent_table is loaded into the dictionary cache, all the child table will also be loaded. This is taking lot of time. Since this operation happens when the dictionary latch is taken, the scenario leads to "long semaphore wait" situation and the server gets killed. Analysis: A simple performance analysis showed that the slowness is because of the dict_foreign_find() function. It does a linear search on two linked list table->foreign_list and table->referenced_list, looking for a particular foreign key object based on foreign->id as the key. This is called two times for each foreign key object. Solution: Introduce a rb tree in table->foreign_rbt and table->referenced_rbt, which are some sort of index on table->foreign_list and table->referenced_list respectively, using foreign->id as the key. These rbt structures will be solely used by dict_foreign_find(). rb#5599 approved by Vasil |
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