Some further research shows this to always be on UPDATE IGNORE queries.
Query (7f4a5c3dc190): UPDATE IGNORE `table500_innodb_default_int` t1, `table500_innodb_compressed` t2 SET t1.`c15` = '07:20:45.059079' WHERE t1.`c13` <= '2009-08-24 14:34:27.013239' Query (7fe6fc0b6200): UPDATE IGNORE `table100_innodb_compressed_int_autoinc` t1, `table100_innodb_dynamic_int` t2 SET t1.`c11` = 0 WHERE t1.`c5` <> 154368 Query (7f6c5c19e230): UPDATE IGNORE `table500_innodb_dynamic_int` t1, `table500_innodb_default` t2 SET t1.`c4` = '2005-11-14' WHERE t1.`c13` <= NULL Query (7fc0d40574c0): UPDATE LOW_PRIORITY IGNORE `table500_innodb_dynamic_int_autoinc` t1, `table500_innodb_compressed_key_pk_parts_2_int_autoinc` t2 SET t1.`c7` = NULL WHERE t1.`c9` = '2005-02-21 12:55:37.061458' Query (7f6c5c19e230): UPDATE IGNORE `table500_innodb_dynamic_int` t1, `table500_innodb_default` t2 SET t1.`c4` = '2005-11-14' WHERE t1.`c13` <= NULL Query (7fc0d40574c0): UPDATE LOW_PRIORITY IGNORE `table500_innodb_dynamic_int_autoinc` t1, `table500_innodb_compressed_key_pk_parts_2_int_autoinc` t2 SET t1.`c7` = NULL WHERE t1.`c9` = '2005-02-21 12:55:37.061458' Query (7f38fc004c10): UPDATE IGNORE `table100_innodb_default_key_pk_parts_2_int_autoinc` t1, `table500_innodb_compressed_int` t2 SET t1.`c16` = -4449792 WHERE t1.`c2` >= 'v' Query (7f4a5c3dc190): UPDATE IGNORE `table500_innodb_default_int` t1, `table500_innodb_compressed` t2 SET t1.`c15` = '07:20:45.059079' WHERE t1.`c13` <= '2009-08-24 14:34:27.013239' Query (7fc0d40574c0): UPDATE LOW_PRIORITY IGNORE `table500_innodb_dynamic_int_autoinc` t1, `table500_innodb_compressed_key_pk_parts_2_int_autoinc` t2 SET t1.`c7` = NULL WHERE t1.`c9` = '2005-02-21 12:55:37.061458'
Some further research shows this to always be on UPDATE IGNORE queries.
Query (7f4a5c3dc190): UPDATE IGNORE `table500_ innodb_ default_ int` t1, `table500_ innodb_ compressed` t2 SET t1.`c15` = '07:20:45.059079' WHERE t1.`c13` <= '2009-08-24 14:34:27.013239' innodb_ compressed_ int_autoinc` t1, `table100_ innodb_ dynamic_ int` t2 SET t1.`c11` = 0 WHERE t1.`c5` <> 154368 innodb_ dynamic_ int` t1, `table500_ innodb_ default` t2 SET t1.`c4` = '2005-11-14' WHERE t1.`c13` <= NULL innodb_ dynamic_ int_autoinc` t1, `table500_ innodb_ compressed_ key_pk_ parts_2_ int_autoinc` t2 SET t1.`c7` = NULL WHERE t1.`c9` = '2005-02-21 12:55:37.061458' innodb_ dynamic_ int` t1, `table500_ innodb_ default` t2 SET t1.`c4` = '2005-11-14' WHERE t1.`c13` <= NULL innodb_ dynamic_ int_autoinc` t1, `table500_ innodb_ compressed_ key_pk_ parts_2_ int_autoinc` t2 SET t1.`c7` = NULL WHERE t1.`c9` = '2005-02-21 12:55:37.061458' innodb_ default_ key_pk_ parts_2_ int_autoinc` t1, `table500_ innodb_ compressed_ int` t2 SET t1.`c16` = -4449792 WHERE t1.`c2` >= 'v' innodb_ default_ int` t1, `table500_ innodb_ compressed` t2 SET t1.`c15` = '07:20:45.059079' WHERE t1.`c13` <= '2009-08-24 14:34:27.013239' innodb_ dynamic_ int_autoinc` t1, `table500_ innodb_ compressed_ key_pk_ parts_2_ int_autoinc` t2 SET t1.`c7` = NULL WHERE t1.`c9` = '2005-02-21 12:55:37.061458'
Query (7fe6fc0b6200): UPDATE IGNORE `table100_
Query (7f6c5c19e230): UPDATE IGNORE `table500_
Query (7fc0d40574c0): UPDATE LOW_PRIORITY IGNORE `table500_
Query (7f6c5c19e230): UPDATE IGNORE `table500_
Query (7fc0d40574c0): UPDATE LOW_PRIORITY IGNORE `table500_
Query (7f38fc004c10): UPDATE IGNORE `table100_
Query (7f4a5c3dc190): UPDATE IGNORE `table500_
Query (7fc0d40574c0): UPDATE LOW_PRIORITY IGNORE `table500_