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MDEV-17772 - 3 way lock : ALTER, MDL, BACKUP STAGE BLOCK_DDL While waiting for a (potentially long) RO transaction or SELECT, DDL and LOCK TABLES ... WRITE hold protection against FTWRL and BACKUP STAGE. This effectively makes FTWRL/BACKUP STAGE indirectly wait for this RO transaction or SELECT to finish. Which is not great, as otherwise we could do something useful meanwhile. With this patch BACKUP lock is attempted to be acquired after TABLE/SCHEMA locks. If this attempt fails, TABLE/SCHEMA locks gets released and we start waiting for BACKUP lock. When wait finishes, BACKUP lock is released (to avoid deadlocks) and we attempt to acquire all locks once again. Other changes: - Take MDL lock before testing if table exists as part of CREATE TABLE ... IF EXISTS. This change was an effect of changes in lock_table_name and removes an inconsistency where one could get different error messages from CREATE TABLE .. IF EXISTS depending on active mdl locks. One effect of this change is that we don't binary log CREATE TABLE IF EXISTS if the table exists. This was done because old code was sometimes behaving inconsistenly (it was logged some time and not other times) and sending the query to the slave could make the slave even more inconsistent as there is not guarantee that the new table will have the same definition as the old table on the master.
40 lines
851 B
Text
40 lines
851 B
Text
########################################################################
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# Tests for BACKUP STAGE locking that requires debug.
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########################################################################
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--source include/have_debug_sync.inc
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--echo #
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--echo # Make sure pending LOCK TABLES doesn't block BACKUP STAGE
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--echo #
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CREATE TABLE t1(a INT);
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LOCK TABLE t1 READ;
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--echo #
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connect (con1,localhost,root,,);
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SET DEBUG_SYNC= 'mdl_acquire_lock_wait SIGNAL ready';
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--send LOCK TABLE t1 WRITE
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--echo #
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connect (con2,localhost,root,,);
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SET DEBUG_SYNC= 'now WAIT_FOR ready';
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BACKUP STAGE START;
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BACKUP STAGE FLUSH;
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BACKUP STAGE BLOCK_DDL;
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BACKUP STAGE END;
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disconnect con2;
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--echo #
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connection default;
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UNLOCK TABLES;
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--echo #
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connection con1;
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reap;
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UNLOCK TABLES;
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disconnect con1;
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--echo #
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connection default;
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DROP TABLE t1;
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SET DEBUG_SYNC= 'RESET';
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