SHOW [GLOBAL|SESSION] BINDINGS

SHOW BINDINGS 语句用于显示创建过的 SQL 绑定的相关信息。BINDING 语句可以在 GLOBAL 或者 SESSION 作用域内显示执行计划绑定。在不指定作用域时,默认的作用域为 SESSION

语法图

ShowStmt:

ShowStmt

ShowTargetFilterable:

ShowTargetFilterable

GlobalScope:

GlobalScope

ShowLikeOrWhereOpt

ShowLikeOrWhereOpt

语法说明

SHOW [GLOBAL | SESSION] BINDINGS [ShowLikeOrWhereOpt];

该语句会输出 GLOBAL 或者 SESSION 作用域内的执行计划绑定,在不指定作用域时默认作用域为 SESSION。目前 SHOW BINDINGS 会输出 8 列,具体如下:

列名说明
original_sql参数化后的原始 SQL
bind_sql带 Hint 的绑定 SQL
default_db默认数据库名
status状态,包括 using(正在使用)、deleted(已删除)、 invalid(无效)、rejected(演进时被拒绝)和 pending verify(等待演进验证)
create_time创建时间
update_time更新时间
charset字符集
collation排序规则
source创建方式,包括 manual (由 create [global] binding 生成)、capture(由 tidb 自动创建生成)和 evolve (由 tidb 自动演进生成)

示例

CREATE TABLE t1 ( id INT NOT NULL PRIMARY KEY auto_increment, b INT NOT NULL, pad VARBINARY(255), INDEX(b) ); Query OK, 0 rows affected (0.07 sec) INSERT INTO t1 SELECT NULL, FLOOR(RAND()*1000), RANDOM_BYTES(255) FROM dual; Query OK, 1 row affected (0.01 sec) Records: 1 Duplicates: 0 Warnings: 0 INSERT INTO t1 SELECT NULL, FLOOR(RAND()*1000), RANDOM_BYTES(255) FROM t1 a JOIN t1 b JOIN t1 c LIMIT 100000; Query OK, 1 row affected (0.00 sec) Records: 1 Duplicates: 0 Warnings: 0 INSERT INTO t1 SELECT NULL, FLOOR(RAND()*1000), RANDOM_BYTES(255) FROM t1 a JOIN t1 b JOIN t1 c LIMIT 100000; Query OK, 8 rows affected (0.00 sec) Records: 8 Duplicates: 0 Warnings: 0 INSERT INTO t1 SELECT NULL, FLOOR(RAND()*1000), RANDOM_BYTES(255) FROM t1 a JOIN t1 b JOIN t1 c LIMIT 100000; Query OK, 1000 rows affected (0.04 sec) Records: 1000 Duplicates: 0 Warnings: 0 INSERT INTO t1 SELECT NULL, FLOOR(RAND()*1000), RANDOM_BYTES(255) FROM t1 a JOIN t1 b JOIN t1 c LIMIT 100000; Query OK, 100000 rows affected (1.74 sec) Records: 100000 Duplicates: 0 Warnings: 0 INSERT INTO t1 SELECT NULL, FLOOR(RAND()*1000), RANDOM_BYTES(255) FROM t1 a JOIN t1 b JOIN t1 c LIMIT 100000; Query OK, 100000 rows affected (2.15 sec) Records: 100000 Duplicates: 0 Warnings: 0 INSERT INTO t1 SELECT NULL, FLOOR(RAND()*1000), RANDOM_BYTES(255) FROM t1 a JOIN t1 b JOIN t1 c LIMIT 100000; Query OK, 100000 rows affected (2.64 sec) Records: 100000 Duplicates: 0 Warnings: 0 SELECT SLEEP(1); +----------+ | SLEEP(1) | +----------+ | 0 | +----------+ 1 row in set (1.00 sec) ANALYZE TABLE t1; Query OK, 0 rows affected (1.33 sec) EXPLAIN ANALYZE SELECT * FROM t1 WHERE b = 123; +-------------------------------+---------+---------+-----------+----------------------+---------------------------------------------------------------------------+-----------------------------------+----------------+------+ | id | estRows | actRows | task | access object | execution info | operator info | memory | disk | +-------------------------------+---------+---------+-----------+----------------------+---------------------------------------------------------------------------+-----------------------------------+----------------+------+ | IndexLookUp_10 | 583.00 | 297 | root | | time:10.545072ms, loops:2, rpc num: 1, rpc time:398.359µs, proc keys:297 | | 109.1484375 KB | N/A | | ├─IndexRangeScan_8(Build) | 583.00 | 297 | cop[tikv] | table:t1, index:b(b) | time:0s, loops:4 | range:[123,123], keep order:false | N/A | N/A | | └─TableRowIDScan_9(Probe) | 583.00 | 297 | cop[tikv] | table:t1 | time:12ms, loops:4 | keep order:false | N/A | N/A | +-------------------------------+---------+---------+-----------+----------------------+---------------------------------------------------------------------------+-----------------------------------+----------------+------+ 3 rows in set (0.02 sec) CREATE SESSION BINDING FOR SELECT * FROM t1 WHERE b = 123 USING SELECT * FROM t1 IGNORE INDEX (b) WHERE b = 123; Query OK, 0 rows affected (0.00 sec) EXPLAIN ANALYZE SELECT * FROM t1 WHERE b = 123; +-------------------------+-----------+---------+-----------+---------------+--------------------------------------------------------------------------------+--------------------+---------------+------+ | id | estRows | actRows | task | access object | execution info | operator info | memory | disk | +-------------------------+-----------+---------+-----------+---------------+--------------------------------------------------------------------------------+--------------------+---------------+------+ | TableReader_7 | 583.00 | 297 | root | | time:222.32506ms, loops:2, rpc num: 1, rpc time:222.078952ms, proc keys:301010 | data:Selection_6 | 88.6640625 KB | N/A | | └─Selection_6 | 583.00 | 297 | cop[tikv] | | time:224ms, loops:298 | eq(test.t1.b, 123) | N/A | N/A | | └─TableFullScan_5 | 301010.00 | 301010 | cop[tikv] | table:t1 | time:220ms, loops:298 | keep order:false | N/A | N/A | +-------------------------+-----------+---------+-----------+---------------+--------------------------------------------------------------------------------+--------------------+---------------+------+ 3 rows in set (0.22 sec) SHOW SESSION BINDINGS\G *************************** 1. row *************************** Original_sql: select * from t1 where b = ? Bind_sql: SELECT * FROM t1 IGNORE INDEX (b) WHERE b = 123 Default_db: test Status: using Create_time: 2020-05-22 14:38:03.456 Update_time: 2020-05-22 14:38:03.456 Charset: utf8mb4 Collation: utf8mb4_0900_ai_ci 1 row in set (0.00 sec)

MySQL 兼容性

SHOW [GLOBAL|SESSION] BINDINGS 语句是 TiDB 对 MySQL 语法的扩展。

另请参阅

文档内容是否有帮助?

下载 PDF文档反馈社区交流
产品
TiDB
TiDB Dedicated
TiDB Serverless
© 2024 PingCAP. All Rights Reserved.
Privacy Policy.