MDEV-36281 DML aborts during online virtual index #3894
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Reason: ======= - InnoDB DML commit aborts the server when InnoDB does online virtual index. During online DDL, concurrent DML commit operation does read the undo log record and their related current version of the clustered index record. Based on the operation, InnoDB do build the old tuple and new tuple for the table. If the concurrent online index can be affected by the operation, InnoDB does build the entry for the index and log the operation. Problematic case is update operation, InnoDB does build the update vector. But while building the old row, InnoDB fails to fill the non-affected virtual column. This lead to server abort while build the entry for index. Fix: === - First, fill the virtual column entries for the new row. Duplicate the old row based on new row and change only the affected fields in old row based on the update vector.
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| set DEBUG_SYNC="now SIGNAL dml_finish"; | ||
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| connection default; | ||
| reap; | ||
| DROP TABLE t1; | ||
| disconnect con1; |
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The disconnect con1 could be executed before switching to connection default.
| SET DEBUG_SYNC = 'innodb_inplace_alter_table_enter SIGNAL dml_start WAIT_FOR dml_finish'; | ||
| send ALTER TABLE t1 ADD INDEX(f5, f2, f4); | ||
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| connection con1; | ||
| set DEBUG_SYNC="now WAIT_FOR dml_start"; | ||
| UPDATE t1 SET f3= f3 + 1; | ||
| set DEBUG_SYNC="now SIGNAL dml_finish"; | ||
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| connection default; | ||
| reap; | ||
| DROP TABLE t1; |
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I had to double check that this is actually testing a scenario where the value of an indexed virtual column f4 AS (f3) in the being-created index on (f5,f2,f4) is changing. Could we add another index, say, ADD INDEX(f3,f5) where only the value of a non-virtual column is changing? And execute both CHECK TABLE t1 EXTENDED and a number of SELECT with FORCE INDEX to display the contents of each created virtual index?
Description
Reason:
for the index and log the operation.
Problematic case is update operation, InnoDB does build the update vector. But while building the old row, InnoDB fails to fill the non-affected virtual column. This lead to server abort while build the entry for index.
Fix:
How can this PR be tested?
./mtr innodb.innodb-index-online
Basing the PR against the correct MariaDB version
mainbranch.PR quality check