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Bug #21025880 DUPLICATE UK VALUES IN READ-COMMITTED (AGAIN)
PROBLEM Whenever we insert in unique secondary index we take shared locks on all possible duplicate record present in the table. But while during a replace on the unique secondary index , we take exclusive and locks on the all duplicate record. When the records are deleted, they are first delete marked and later purged by the purge thread. While purging the record we call the lock_update_delete() which in turn calls lock_rec_inherit_to_gap() to inherit locks of the deleted records. In repeatable read mode we inherit all the locks from the record to the next record but in the read commited mode we skip inherting them as gap type locks. We make a exception here if the lock on the records is in shared mode ,we assume that it is set during insert for unique secondary index and needs to be inherited to stop constraint violation. We didnt handle the case when exclusive locks are set during replace, we skip inheriting locks of these records and hence causing constraint violation. FIX While inheriting the locks,check whether the transaction is allowed to do TRX_DUP_REPLACE/TRX_DUP_IGNORE, if true inherit the locks. [ Revewied by Jimmy #rb9709]
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