Recently I am handing a SQL issue, I have two transaction, the transaction A first got the Next-Key Locks, and the transaction B tried to get the same lock, so it was waiting, then the transaction A tried to get Insert Intention Locks, so the deadlock happened. But I am confuse that why would this happens?

Here is my table structure:

CREATE TABLE `changeset` (

  `id` int(10) unsigned NOT NULL AUTO_INCREMENT',    

  `userId` int(10) NOT NULL COMMENT,    

  `documentId` varchar(20) NOT NULL,    

  `memberId` bigint(13) NOT NULL,    

  `createTime` bigint(13) NOT NULL,    

  `version` bigint(13) NOT NULL COMMENT,    

  `changesets` mediumtext,    

  PRIMARY KEY (`id`),    

  UNIQUE KEY `uniq_documentId_version` (`documentId`,`version`) USING BTREE    

) ENGINE=InnoDB AUTO_INCREMENT=85771623 DEFAULT CHARSET=utf8

And here is my deadlock log:

(1) TRANSACTION:

TRANSACTION 22640, ACTIVE 66 sec starting index read

mysql tables in use 1, locked 1

LOCK WAIT 2 lock struct(s), heap size 1136, 1 row lock(s)

MySQL thread id 209, OS thread handle 123145559986176, query id 6204
localhost root Sending data

select * from changeset where documentId = '7oO5C_v' and version >=
13 for update

(1) WAITING FOR THIS LOCK TO BE GRANTED:

RECORD LOCKS space id 107 page no 15 n bits 704 index
uniq_documentId_version of table test.changeset trx id 22640
lock_mode X waiting

Record lock, heap no 2 PHYSICAL RECORD: n_fields 3; compact format;
info bits 0

0: len 7; hex 3976735431644a; asc 9vsT1dJ;;

1: len 8; hex 8000000000000000; asc ;;

2: len 4; hex 051cbef7; asc ;;

(2) TRANSACTION:

TRANSACTION 22639, ACTIVE 95 sec inserting

mysql tables in use 1, locked 1

6 lock struct(s), heap size 1136, 4 row lock(s), undo log entries 1

MySQL thread id 212, OS thread handle 123145561657344, query id 6210
localhost root update insert into changeset values (0, 9, '7oO5C_v',
814, 1, 13, 'x')

(2) HOLDS THE LOCK(S):

RECORD LOCKS space id 107 page no 15 n bits 704 index
uniq_documentId_version of table test.changeset trx id 22639
lock_mode X

Record lock, heap no 2 PHYSICAL RECORD: n_fields 3; compact format;
info bits 0

0: len 7; hex 3976735431644a; asc 9vsT1dJ;;

1: len 8; hex 8000000000000000; asc ;;

2: len 4; hex 051cbef7; asc ;;

(2) WAITING FOR THIS LOCK TO BE GRANTED:

RECORD LOCKS space id 107 page no 15 n bits 704 index
uniq_documentId_version of table test.changeset trx id 22639
lock_mode X locks gap before rec insert intention waiting

Record lock, heap no 2 PHYSICAL RECORD: n_fields 3; compact format;
info bits 0

0: len 7; hex 3976735431644a; asc 9vsT1dJ;;

1: len 8; hex 8000000000000000; asc ;;

2: len 4; hex 051cbef7; asc ;;

WE ROLL BACK TRANSACTION (1)

Have you used "(nolock) " in your selects?

Select * From Table with (nolock)