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This article mainly explains the "mysql innodb line lock example analysis", the article explains the content is simple and clear, easy to learn and understand, now please follow the editor's train of thought slowly in depth, together to study and learn "mysql innodb row lock example analysis"!

The real decision on whether to execute the row to be locked is not the row taken out, but the row that is scanned.

Whether the scan record is most indexed or not has something to do with the specific implementation plan.

So when analyzing the lock problem, don't forget to look at the implementation plan.

Session 1: since name is of type varchar, there is an implicit conversion, so all records are scanned and locked.

Root@sakila 10:33:04 > explain select * from tab_no_index where name=1 for update

+-- +

| | id | select_type | table | type | possible_keys | key | key_len | ref | rows | Extra |

+-- +

| | 1 | SIMPLE | tab_no_index | ALL | name | NULL | NULL | NULL | 6 | Using where |

+-- +

1 row in set (0.00 sec)

Root@sakila 10:34:30 > select * from tab_no_index where name=1 for update

+-+ +

| | id | name |

+-+ +

| | 1 | 1 |

+-+ +

1 row in set (0.00 sec)

Session 2: even if the updated record is different from the record selected by answer 1, the update lock cannot be applied because the record was scanned by the first session and locked.

Root@sakila 10:34:35 > select * from tab_no_index where name='4' for update

ERROR 1205 (HY000): Lock wait timeout exceeded; try restarting transaction

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