TIDB_TRX
TIDB_TRX
表提供关于当前在 TiDB 节点上执行的事务的信息。
USE INFORMATION_SCHEMA;
DESC TIDB_TRX;
输出结果如下:
+-------------------------+-----------------------------------------------------------------+------+------+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+-------------------------+-----------------------------------------------------------------+------+------+---------+-------+
| ID | bigint(21) unsigned | NO | PRI | NULL | |
| START_TIME | timestamp(6) | YES | | NULL | |
| CURRENT_SQL_DIGEST | varchar(64) | YES | | NULL | |
| CURRENT_SQL_DIGEST_TEXT | text | YES | | NULL | |
| STATE | enum('Idle','Running','LockWaiting','Committing','RollingBack') | YES | | NULL | |
| WAITING_START_TIME | timestamp(6) | YES | | NULL | |
| MEM_BUFFER_KEYS | bigint(64) | YES | | NULL | |
| MEM_BUFFER_BYTES | bigint(64) | YES | | NULL | |
| SESSION_ID | bigint(21) unsigned | YES | | NULL | |
| USER | varchar(16) | YES | | NULL | |
| DB | varchar(64) | YES | | NULL | |
| ALL_SQL_DIGESTS | text | YES | | NULL | |
| RELATED_TABLE_IDS | text | YES | | NULL | |
+-------------------------+-----------------------------------------------------------------+------+------+---------+-------+
TIDB_TRX
表中每个字段的含义如下:
ID
:事务 ID,即事务的start_ts
(开始时间戳)。START_TIME
:事务的开始时间,即对应事务的start_ts
的物理时间。CURRENT_SQL_DIGEST
:事务当前正在执行的 SQL 语句的 digest。CURRENT_SQL_DIGEST_TEXT
:事务当前执行的 SQL 语句的规范化形式,即不带参数和格式的 SQL 语句。它对应CURRENT_SQL_DIGEST
。STATE
:事务的当前状态。可能的取值包括:Idle
:事务处于空闲状态,即等待用户输入查询。Running
:事务正在执行查询。LockWaiting
:事务正在等待获取悲观锁。注意,事务在开始悲观锁操作时,无论是否被其他事务阻塞,都会进入此状态。Committing
:事务正在提交中。RollingBack
:事务正在回滚。
WAITING_START_TIME
:当STATE
为LockWaiting
时,此列显示等待开始的时间。MEM_BUFFER_KEYS
:当前事务写入内存缓冲区的键数量。MEM_BUFFER_BYTES
:当前事务写入内存缓冲区的键值对总字节数。SESSION_ID
:所属会话的 ID。USER
:执行事务的用户名称。DB
:事务执行时的当前默认数据库名称。ALL_SQL_DIGESTS
:事务已执行的语句的 digest 列表。以 JSON 格式的字符串数组显示。每个事务最多记录前 50 条语句。可以使用TIDB_DECODE_SQL_DIGESTS
函数,将此列中的信息转换为对应的规范化 SQL 语句列表。RELATED_TABLE_IDS
:事务访问的表、视图及其他对象的 ID 列表。
Example
查看 TIDB_TRX
表:
SELECT * FROM INFORMATION_SCHEMA.TIDB_TRX\G
输出结果如下:
*************************** 1. row ***************************
ID: 426789913200689153
START_TIME: 2021-08-04 10:51:54.883000
CURRENT_SQL_DIGEST: NULL
CURRENT_SQL_DIGEST_TEXT: NULL
STATE: Idle
WAITING_START_TIME: NULL
MEM_BUFFER_KEYS: 1
MEM_BUFFER_BYTES: 29
SESSION_ID: 7
USER: root
DB: test
ALL_SQL_DIGESTS: ["e6f07d43b5c21db0fbb9a31feac2dc599787763393dd5acbfad80e247eb02ad5","04fa858fa491c62d194faec2ab427261cc7998b3f1ccf8f6844febca504cb5e9","b83710fa8ab7df8504920e8569e48654f621cf828afbe7527fd003b79f48da9e"]
*************************** 2. row ***************************
ID: 426789921471332353
START_TIME: 2021-08-04 10:52:26.433000
CURRENT_SQL_DIGEST: 38b03afa5debbdf0326a014dbe5012a62c51957f1982b3093e748460f8b00821
CURRENT_SQL_DIGEST_TEXT: update `t` set `v` = `v` + ? where `id` = ?
STATE: LockWaiting
WAITING_START_TIME: 2021-08-04 10:52:35.106568
MEM_BUFFER_KEYS: 0
MEM_BUFFER_BYTES: 0
SESSION_ID: 9
USER: root
DB: test
ALL_SQL_DIGESTS: ["e6f07d43b5c21db0fbb9a31feac2dc599787763393dd5acbfad80e247eb02ad5","38b03afa5debbdf0326a014dbe5012a62c51957f1982b3093e748460f8b00821"]
2 rows in set (0.01 sec)
从此示例的查询结果可以看出:当前节点有两个正在进行的事务。一个事务处于空闲状态(STATE
为 Idle
,CURRENT_SQL_DIGEST
为 NULL
),该事务已执行了 3 条语句(ALL_SQL_DIGESTS
列表中有三条记录,分别是已执行的三条 SQL 语句的 digest)。另一个事务正在执行语句并等待锁(STATE
为 LockWaiting
,WAITING_START_TIME
显示等待锁的开始时间)。该事务已执行 2 条语句,当前正在执行的语句为 "update `t` set `v` = `v` + ? where `id` = ?"
。
SELECT id, all_sql_digests, tidb_decode_sql_digests(all_sql_digests) AS all_sqls FROM INFORMATION_SCHEMA.TIDB_TRX\G
输出结果如下:
*************************** 1. row ***************************
id: 426789913200689153
all_sql_digests: ["e6f07d43b5c21db0fbb9a31feac2dc599787763393dd5acbfad80e247eb02ad5","04fa858fa491c62d194faec2ab427261cc7998b3f1ccf8f6844febca504cb5e9","b83710fa8ab7df8504920e8569e48654f621cf828afbe7527fd003b79f48da9e"]
all_sqls: ["begin","insert into `t` values ( ... )","update `t` set `v` = `v` + ?"]
*************************** 2. row ***************************
id: 426789921471332353
all_sql_digests: ["e6f07d43b5c21db0fbb9a31feac2dc599787763393dd5acbfad80e247eb02ad5","38b03afa5debbdf0326a014dbe5012a62c51957f1982b3093e748460f8b00821"]
all_sqls: ["begin","update `t` set `v` = `v` + ? where `id` = ?"]
此查询调用了 TIDB_DECODE_SQL_DIGESTS
函数,将 TIDB_TRX
表中 ALL_SQL_DIGESTS
列的 SQL digest 数组转换为规范化 SQL 语句数组,通过系统内部查询帮助你直观获取事务历史执行的语句信息。然而,注意上述查询会扫描整个 TIDB_TRX
表,并对每一行调用 TIDB_DECODE_SQL_DIGESTS
函数,调用此函数的开销较大。因此,如果集群中存在大量并发事务,建议避免使用此类查询。
CLUSTER_TIDB_TRX
TIDB_TRX
表仅提供单个 TiDB 节点上正在执行的事务信息。如果你想查看整个集群中所有 TiDB 节点上正在执行的事务信息,需要查询 CLUSTER_TIDB_TRX
表。与 TIDB_TRX
表的查询结果相比,CLUSTER_TIDB_TRX
表的查询结果多了一个 INSTANCE
字段。INSTANCE
字段显示集群中每个节点的 IP 地址和端口,用于区分事务所在的 TiDB 节点。
USE INFORMATION_SCHEMA;
DESC CLUSTER_TIDB_TRX;
输出结果如下:
+-------------------------+-----------------------------------------------------------------+------+------+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+-------------------------+-----------------------------------------------------------------+------+------+---------+-------+
| INSTANCE | varchar(64) | YES | | NULL | |
| ID | bigint(21) unsigned | NO | PRI | NULL | |
| START_TIME | timestamp(6) | YES | | NULL | |
| CURRENT_SQL_DIGEST | varchar(64) | YES | | NULL | |
| CURRENT_SQL_DIGEST_TEXT | text | YES | | NULL | |
| STATE | enum('Idle','Running','LockWaiting','Committing','RollingBack') | YES | | NULL | |
| WAITING_START_TIME | timestamp(6) | YES | | NULL | |
| MEM_BUFFER_KEYS | bigint(64) | YES | | NULL | |
| MEM_BUFFER_BYTES | bigint(64) | YES | | NULL | |
| SESSION_ID | bigint(21) unsigned | YES | | NULL | |
| USER | varchar(16) | YES | | NULL | |
| DB | varchar(64) | YES | | NULL | |
| ALL_SQL_DIGESTS | text | YES | | NULL | |
| RELATED_TABLE_IDS | text | YES | | NULL | |
+-------------------------+-----------------------------------------------------------------+------+------+---------+-------+
14 rows in set (0.00 sec)