本文是一个说明文档，主要是为MySQL和Innodb做了两个比较简单的输出功能用于便于大家学习这两种锁，其实这个方法也是我学习的时候用到的：
- MySQL 层 MDL LOCK
- Innodb 层ROW LOCK
但是由于能力有限肯定有考虑不周的地方，请指出。
参数名字gaopeng用于快速查找自己加入的参数标志。
仅用于学习测试。
一、新加入的参数和保留的参数
mysql> show variables like '%gaopeng%';
+--------------------------------+-------+
| Variable_name | Value |
+--------------------------------+-------+
| gaopeng_mdl_detail | OFF |
| innodb_gaopeng_row_lock_detail | ON |
+--------------------------------+-------+- gaopeng_mdl_detail:默认OFF，可以设置ON 用于打印MDL LOCK获取、等待、升级、降级、释放日志到errlog(GOBAL)，并且可以在show engine中获取
- innodb_gaopeng_row_lock_detail:默认OFF，可以设置为ON，用于打印innodb ROW LOCK获取日志、等待日志、隐含锁转换日志等到errlog，并且可以在show engine中获取详细锁链表信息(注意
没有行的详细信息需要开启innodb_show_verbose_locks) 到errlog(GLOBAL)。但是没有做表级印象锁输出。 - 保留原有参数
innodb_show_verbose_locks:默认为0，设置为1，可以在show engine中获取锁定的行详细信息。
二、测试概要
- MySQL MDL LOCK
也就是如果要MDL LOCK测试设置如下:
set global gaopeng_mdl_detail=1;
重新登陆后每次获取MDL LOCK信息会得到日志，下面是一个select语句获取MDL LOCK和释放的日志：
2018-09-01T20:32:07.090351+08:00 11 [Note] [Call Acquire_lock] THIS MDL LOCK acquire [OK]:
2018-09-01T20:32:07.090503+08:00 11 [Note](>MDL PRINT) |Thread id is 11|Current_state: Opening tables|
2018-09-01T20:32:07.090542+08:00 11 [Note](->MDL PRINT) DB_name is:test
2018-09-01T20:32:07.090571+08:00 11 [Note](-->MDL PRINT) OBJ_name is:kkkpk
2018-09-01T20:32:07.090595+08:00 11 [Note](--->MDL PRINT) Namespace is:TABLE
2018-09-01T20:32:07.090608+08:00 11 [Note](---->MDL PRINT) Fast path is:(Y)
2018-09-01T20:32:07.090621+08:00 11 [Note](----->MDL PRINT) Mdl type is:MDL_SHARED_READ(SR)
2018-09-01T20:32:07.090635+08:00 11 [Note](------->MDL PRINT) Mdl status is:EMPTY
2018-09-01T20:32:07.091077+08:00 11 [Note] [Call release_lock] this MDL LOCK will [RELEASE]:
2018-09-01T20:32:07.091168+08:00 11 [Note](>MDL PRINT) |Thread id is 11|Current_state: closing tables|
2018-09-01T20:32:07.091197+08:00 11 [Note](->MDL PRINT) DB_name is:test
2018-09-01T20:32:07.091210+08:00 11 [Note](-->MDL PRINT) OBJ_name is:kkkpk
2018-09-01T20:32:07.091241+08:00 11 [Note](--->MDL PRINT) Namespace is:TABLE
2018-09-01T20:32:07.091254+08:00 11 [Note](---->MDL PRINT) Fast path is:(Y)
2018-09-01T20:32:07.091267+08:00 11 [Note](----->MDL PRINT) Mdl type is:MDL_SHARED_READ(SR)
2018-09-01T20:32:07.091280+08:00 11 [Note](------->MDL PRINT) Mdl status is:EMPTY - Innodb ROW LOCK
如果需要INNODB ROW LOCK加锁测试可以设置如下:
set global innodb_gaopeng_row_lock_detail=1;
set innodb_show_verbose_locks=1;
重新登陆，下面是一个insert唯一性检查锁定的日志：
2018-09-01T20:26:08.809304+08:00 10 [Note] InnoDB: This TRX help other TRX convert impl lock to expl lock!!!insert often use impl lock!!!!
2018-09-01T20:26:08.809422+08:00 10 [Note] InnoDB: Other TRX:
2018-09-01T20:26:08.809477+08:00 10 [Note] InnoDB: TRX ID:(1294) table:test/kkkpk index:PRIMARY space_id: 28 page_id:3 heap_no:2 row lock mode:LOCK_X|LOCK_NOT_GAP|
PHYSICAL RECORD: n_fields 3; compact format; info bits 0
0: len 4; hex 80000001; asc ;;
1: len 6; hex 00000000050e; asc ;;
2: len 7; hex ae0000001e0110; asc ;;
2018-09-01T20:26:08.809824+08:00 10 [Note] InnoDB: This TRX:
2018-09-01T20:26:08.809851+08:00 10 [Note] InnoDB: TRX ID:(1295) table:test/kkkpk index:PRIMARY space_id: 28 page_id:3 heap_no:2 row lock mode:LOCK_S|LOCK_NOT_GAP|
PHYSICAL RECORD: n_fields 3; compact format; info bits 0
0: len 4; hex 80000001; asc ;;
1: len 6; hex 00000000050e; asc ;;
2: len 7; hex ae0000001e0110; asc ;;
2018-09-01T20:26:08.810401+08:00 10 [Note] InnoDB: Trx(1295) is blocked!!!!!show engine 也会得到如下记录：
---TRANSACTION 1295, ACTIVE 101 sec inserting
mysql tables in use 1, locked 1
LOCK WAIT 2 lock struct(s), heap size 1136, 1 row lock(s)
MySQL thread id 10, OS thread handle 139670301562624, query id 55 localhost root update
insert into kkkpk values(1)
------- TRX HAS BEEN WAITING 101 SEC FOR THIS LOCK TO BE GRANTED:
RECORD LOCKS space id 28 page no 3 n bits 72 index PRIMARY of table `test`.`kkkpk` trx id 1295 lock mode S(LOCK_S) locks rec but not gap(LOCK_REC_NOT_GAP) waiting(LOCK_WAIT)
Record lock, heap no 2 PHYSICAL RECORD: n_fields 3; compact format; info bits 0
0: len 4; hex 80000001; asc ;;
1: len 6; hex 00000000050e; asc ;;
2: len 7; hex ae0000001e0110; asc ;;
------------------
TABLE LOCK table `test`.`kkkpk` trx id 1295 lock mode IX
RECORD LOCKS space id 28 page no 3 n bits 72 index PRIMARY of table `test`.`kkkpk` trx id 1295 lock mode S(LOCK_S) locks rec but not gap(LOCK_REC_NOT_GAP) waiting(LOCK_WAIT)
Record lock, heap no 2 PHYSICAL RECORD: n_fields 3; compact format; info bits 0
0: len 4; hex 80000001; asc ;;
1: len 6; hex 00000000050e; asc ;;
2: len 7; hex ae0000001e0110; asc ;;
---TRANSACTION 1294, ACTIVE 132 sec
2 lock struct(s), heap size 1136, 1 row lock(s), undo log entries 1
MySQL thread id 9, OS thread handle 139670301828864, query id 56 localhost root starting
show engine innodb status
TABLE LOCK table `test`.`kkkpk` trx id 1294 lock mode IX
RECORD LOCKS space id 28 page no 3 n bits 72 index PRIMARY of table `test`.`kkkpk` trx id 1294 lock_mode X(LOCK_X) locks rec but not gap(LOCK_REC_NOT_GAP)
Record lock, heap no 2 PHYSICAL RECORD: n_fields 3; compact format; info bits 0
0: len 4; hex 80000001; asc ;;
1: len 6; hex 00000000050e; asc ;;
2: len 7; hex ae0000001e0110; asc ;;可以看到等待即输出一致事物1295 处于等待状态，锁模式一致。
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