| title | summary | aliases | |
|---|---|---|---|
SHOW [GLOBAL|SESSION] BINDINGS |
Use of SHOW BINDINGS binding in TiDB database. |
|
The SHOW BINDINGS statement is used to display information about created SQL bindings. A BINDING can be on either a GLOBAL or SESSION basis. The default is SESSION.
ShowBindingsStmt ::=
"SHOW" ("GLOBAL" | "SESSION")? "BINDINGS" ShowLikeOrWhere?
ShowLikeOrWhere ::=
"LIKE" SimpleExpr
| "WHERE" Expression
This statement outputs the execution plan bindings at the GLOBAL or SESSION level. The default scope is SESSION. Currently SHOW BINDINGS outputs eight columns, as shown below:
| Column Name | Description |
|---|---|
| original_sql | Original SQL statement after parameterization |
| bind_sql | Bound SQL statement with hints |
| default_db | Default database |
| status | Status including 'Using', 'Deleted', 'Invalid', 'Rejected', and 'Pending verification' |
| create_time | Created time |
| update_time | Updated time |
| charset | Character set |
| collation | Sorting rule |
| source | The way in which a binding is created, including manual (created by the create [global] binding SQL statement), capture (captured automatically by TiDB), and evolve (evolved automatically by TiDB) |
mysql> 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)
mysql> 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
mysql> 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
mysql> 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
mysql> 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
mysql> 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
mysql> 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
mysql> 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
mysql> SELECT SLEEP(1);
+----------+
| SLEEP(1) |
+----------+
| 0 |
+----------+
1 row in set (1.00 sec)
mysql> ANALYZE TABLE t1;
Query OK, 0 rows affected (1.33 sec)
mysql> 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)
mysql> 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)
mysql> 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)
mysql> 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)This statement is a TiDB extension to MySQL syntax.