Transaction isolation level gap lock deadlock

1. Transaction isolation level

1. serialize （SERIALIZABLE）
2. Repeatable （REPEATABLE READ）
3. Submit to read （READ COMMITTED）
4. Uncommitted read （READ UNCOMMITTED）

The four isolation levels correspond to addition, deletion, modification and query

2.gap Lock analysis ：

Uncommitted read （READ UNCOMMITTED）: Add, delete, change and check without locking .
Submit to read （READ COMMITTED）： Increase the time to lock the index a certain distance （ If the index is 12, Lock an index in 12 A distance up and down ）, Release the lock when the transaction is committed .
Repeatable （REPEATABLE READ）： Lock the index for a distance when adding, deleting or modifying data （insert Above , If the index is 12, Then lock the distance between the indexes of the previous row and the next row , If there is no previous line or next line , Then lock a distance ）
serialize （SERIALIZABLE）： Add, delete, change and check will be locked , Transactions can only be committed one by one , The obtained transaction locks the table directly

3.gap Deadlock

Two transaction colleagues obtained an interval lock , And simultaneously operate the interval

111    delete from ts_column_log_test wherecol_id=10;

222   delete from ts_column_log_test where col_id=11;

111   INSERT INTO ts_column_log_test (col_id,start_time, end_time, data_time, status) VALUES (10, NULL, NULL, '20111209','running');

222  INSERT INTO ts_column_log_test (col_id, start_time, end_time,data_time, status) VALUES (11, NULL, NULL, '20111209', 'running');

This is the time , You may get an error message ERROR 1213 (40001): Deadlock found when trying toget lock; try restarting transaction.

The reason is that the first two statements have been obtained [2,20) Recorded in this interval S lock , Then, the two transactions are performed on col_id=10 This location request X lock , Then a deadlock occurs , No one can ask X lock , Because they both hold S lock .