zz 通过INFORMATION_SCHEMA.INNODB_TRX、INNODB_LOCKS、INNODB_LOCK_WAITS 三个表获取事务与锁的信息

zz from http://imysql.com/2015/03/25/mysql-faq-how-to-fetch-latest-trxid.shtml
#先查询 INNODB_TRX 表，看看都有哪些事务

mysql> SELECT * FROM INFORMATION_SCHEMA.INNODB_TRX\G
*************************** 1. row ***************************
trx_id: 17778 -- 当前事务ID
trx_state: LOCK WAIT -- 处于锁等待状态，也就是等待其他会话释放锁资源
trx_started: 2015-03-04 10:40:26
trx_requested_lock_id: 17778:82:3:6 -- 欲请求的锁
trx_wait_started: 2015-03-04 10:40:26
trx_weight: 2 -- 大意是该锁影响了2行记录
trx_mysql_thread_id: 657 -- processlist中的线程ID
trx_query: update trx_fee set fee=rand()*1000 where id= 4
trx_operation_state: starting index read
trx_tables_in_use: 1
trx_tables_locked: 1
trx_lock_structs: 2
trx_lock_memory_bytes: 360
trx_rows_locked: 1
trx_rows_modified: 0
trx_concurrency_tickets: 0
trx_isolation_level: REPEATABLE READ
trx_unique_checks: 1
trx_foreign_key_checks: 1
trx_last_foreign_key_error: NULL
trx_adaptive_hash_latched: 0
trx_adaptive_hash_timeout: 10000
trx_is_read_only: 0
trx_autocommit_non_locking: 0
*************************** 2. row ***************************
trx_id: 17773
trx_state: RUNNING
trx_started: 2015-03-04 10:40:23
trx_requested_lock_id: NULL
trx_wait_started: NULL
trx_weight: 10
trx_mysql_thread_id: 656
trx_query: NULL
trx_operation_state: NULL
trx_tables_in_use: 0
trx_tables_locked: 0
trx_lock_structs: 2
trx_lock_memory_bytes: 360
trx_rows_locked: 9
trx_rows_modified: 8
trx_concurrency_tickets: 0
trx_isolation_level: REPEATABLE READ
trx_unique_checks: 1
trx_foreign_key_checks: 1
trx_last_foreign_key_error: NULL
trx_adaptive_hash_latched: 0
trx_adaptive_hash_timeout: 10000
trx_is_read_only: 0
trx_autocommit_non_locking: 0

#再看 INNODB_LOCKS 表，看看都有什么锁

mysql> select * from information_schema.INNODB_LOCKS\G
*************************** 1. row ***************************
lock_id: 17778:82:3:6 --当前锁ID
lock_trx_id: 17778 --该锁对应的事务ID
lock_mode: X -- 锁类型，排它锁X
lock_type: RECORD --锁范围，记录锁：record lock，其他锁范围：间隙锁：gap lock，或者next-key lock（记录锁+间隙锁）
lock_table: `test`.`trx_fee`
lock_index: PRIMARY --加载在哪个索引上的锁
lock_space: 82
lock_page: 3
lock_rec: 6
lock_data: 4
*************************** 2. row ***************************
lock_id: 17773:82:3:6
lock_trx_id: 17773
lock_mode: X
lock_type: RECORD
lock_table: `test`.`trx_fee`
lock_index: PRIMARY
lock_space: 82
lock_page: 3
lock_rec: 6
lock_data: 4

#最后看 INNODB_LOCK_WAITS 表，看看当前都有哪些锁等待

mysql> select * from information_schema.INNODB_LOCK_WAITS\G
*************************** 1. row ***************************
requesting_trx_id: 17778 --请求锁的事务ID（等待方）
requested_lock_id: 17778:82:3:6 -- 请求锁ID
blocking_trx_id: 17773 -- 阻塞该锁的事务ID（当前持有方，待释放）
blocking_lock_id: 17773:82:3:6 -- 持有的锁ID

关于INFORMATION_SCHEMA中和InnoDB有关的表用途描述，可以查看手册：21.29 INFORMATION_SCHEMA Tables for InnoDB