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  1. MariaDB Server
  2. MDEV-17158

TRUNCATE is not atomic after MDEV-13564

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    Description

      I observed this both on 10.2 and 10.3 when testing MDEV-13564. The following test would occasionally fail on a cmake -DCMAKE_BUILD_TYPE=Debug -DWITH_ASAN=1 build:

      ./mtr --parallel=40 --repeat=100 --mysqld=--debug=d,ib_log innodb.truncate_crash{,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,}

      The reason for this appears to be that the following call does not always guarantee a write to the redo log:

      log_write_up_to(mtr.commit_lsn(), true);

      Such a call is present in all callers of fil_name_write_rename_low(), yet sometimes we end up with losing the table, because no undo log was persisted for the incomplete transaction despite this call.

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          relates to

          Bug - A problem which impairs or prevents the functions of the product. MDEV-13564 TRUNCATE TABLE and undo tablespace truncation are not compatible with Mariabackup

          • Major - Major loss of function.
          • Closed

          Bug - A problem which impairs or prevents the functions of the product. MDEV-14717 RENAME TABLE in InnoDB is not crash-safe

          • Major - Major loss of function.
          • Closed

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            elenst Elena Stepanova added a comment -

            The test fails for me like this:

            innodb.truncate_crash 'innodb'           w4 [ 52 fail ]
            		 
                    Test ended at 2018-09-07 23:06:13
            		 
             
            		 
            CURRENT_TEST: innodb.truncate_crash
            		 
            mysqltest: At line 20: query 'SELECT * FROM t1' failed: 1932: Table 'test.t1' doesn't exist in engine

            If it's not an indication of the reported problem, then could you please paste the output which does indicate it?

            elenst Elena Stepanova added a comment - The test fails for me like this: innodb.truncate_crash 'innodb' w4 [ 52 fail ] Test ended at 2018-09-07 23:06:13   CURRENT_TEST: innodb.truncate_crash mysqltest: At line 20: query 'SELECT * FROM t1' failed: 1932: Table 'test.t1' doesn't exist in engine If it's not an indication of the reported problem, then could you please paste the output which does indicate it?
            marko Marko Mäkelä added a comment -

            I made a wrong diagnosis. log_write_up_to() appears to behave as it should. The actual problem is in MDEV-13564: ha_innobase::truncate() will invoke innobase_rename_table(), which will commit the transaction prematurely. Because of this, the original table would be persistently renamed to a temporary name before the new empty table has been created.

            marko Marko Mäkelä added a comment - I made a wrong diagnosis. log_write_up_to() appears to behave as it should. The actual problem is in MDEV-13564 : ha_innobase::truncate() will invoke innobase_rename_table() , which will commit the transaction prematurely. Because of this, the original table would be persistently renamed to a temporary name before the new empty table has been created.
            marko Marko Mäkelä added a comment -

            It turned out that there were multiple InnoDB transaction commits inside ha_innobase::truncate() before the completion of ha_innobase::create(). Also the crash recovery had to be revised a bit, because the new empty file has to be deleted before the old non-empty table can be renamed back to the old file.

            marko Marko Mäkelä added a comment - It turned out that there were multiple InnoDB transaction commits inside ha_innobase::truncate() before the completion of ha_innobase::create() . Also the crash recovery had to be revised a bit, because the new empty file has to be deleted before the old non-empty table can be renamed back to the old file.

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              marko Marko Mäkelä
              marko Marko Mäkelä
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