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time-and-fate authored Aug 15, 2024
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30 changes: 15 additions & 15 deletions sql-plan-management.md
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Original file line number Diff line number Diff line change
Expand Up @@ -223,27 +223,27 @@ CREATE BINDING FOR SELECT * FROM t WHERE a > 1 USING SELECT * FROM t use index(i
#### 根据历史执行计划创建绑定

如需将 SQL 语句的执行计划固定为之前使用过的执行计划，可以使用 `plan_digest` 为该 SQL 语句绑定一个历史的执行计划。相比于使用 SQL 创建绑定的方式，此方式更加简便。
如需将 SQL 语句的执行计划固定为之前使用过的执行计划，可以使用 Plan Digest 为该 SQL 语句绑定一个历史的执行计划。相比于使用 SQL 创建绑定的方式，此方式更加简便，并且支持一次为多个语句绑定执行计划。详细说明和更多示例参见 [`CREATE [GLOBAL|SESSION] BINDING`](/sql-statements/sql-statement-create-binding.md)。

以下为根据历史执行计划创建绑定的注意事项：

- 该功能是根据历史的执行计划生成 hint 而实现的绑定，历史的执行计划来源是 [Statement Summary Tables](/statement-summary-tables.md)，因此在使用此功能之前需开启系统变量 [`tidb_enable_stmt_summary`](/system-variables.md#tidb_enable_stmt_summary-从-v304-版本开始引入)。
- 对于包含子查询的查询、访问 TiFlash 的查询、3 张表或更多表进行 Join 的查询，自动生成的 hint 不够完备，可能导致无法完全固定住计划，对于这类情况在创建时会产生告警。
- 原执行计划对应 SQL 语句中的 hint 也会被应用在创建的绑定中，如执行 `SELECT /*+ max_execution_time(1000) */ * FROM t` 后，使用其 `plan_digest` 创建的绑定中会带上 `max_execution_time(1000)`。
- 原执行计划对应 SQL 语句中的 hint 也会被应用在创建的绑定中，如执行 `SELECT /*+ max_execution_time(1000) */ * FROM t` 后，使用其 Plan Digest 创建的绑定中会带上 `max_execution_time(1000)`。

使用方式:
使用方式：

```sql
CREATE [GLOBAL | SESSION] BINDING FROM HISTORY USING PLAN DIGEST 'plan_digest';
CREATE [GLOBAL | SESSION] BINDING FROM HISTORY USING PLAN DIGEST StringLiteralOrUserVariableList;
```

该语句使用 `plan_digest` 为 SQL 语句绑定执行计划，在不指定作用域时默认作用域为 SESSION。所创建绑定的适用 SQL、优先级、作用域、生效条件等与[根据 SQL 创建绑定](#根据-sql-创建绑定)相同。
该语句使用 Plan Digest 为 SQL 语句绑定执行计划，在不指定作用域时默认作用域为 SESSION。所创建绑定的适用 SQL、优先级、作用域、生效条件等与[根据 SQL 创建绑定](#根据-sql-创建绑定)相同。

使用此绑定方式时，你需要先从 `statements_summary` 中找到需要绑定的执行计划对应的 `plan_digest`，再通过 `plan_digest` 创建绑定。具体步骤如下：
使用此绑定方式时，你需要先从 `statements_summary` 中找到需要绑定的执行计划对应的 Plan Digest，再通过 Plan Digest 创建绑定。具体步骤如下：

1. 从 `Statement Summary Tables` 的记录中查找执行计划对应的 `plan_digest`。
1. 从 `Statement Summary Tables` 的记录中查找执行计划对应的 Plan Digest。

例如:
例如：

```sql
CREATE TABLE t(id INT PRIMARY KEY , a INT, KEY(a));
Expand All @@ -266,9 +266,9 @@ CREATE [GLOBAL | SESSION] BINDING FROM HISTORY USING PLAN DIGEST 'plan_digest';
BINARY_PLAN: 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
```

可以看到执行计划对应的 `plan_digest` 为 `4e3159169cc63c14b139a4e7d72eae1759875c9a9581f94bb2079aae961189cb`。
可以看到执行计划对应的 Plan Digest 为 `4e3159169cc63c14b139a4e7d72eae1759875c9a9581f94bb2079aae961189cb`。

2. 使用 `plan_digest` 创建绑定。
2. 使用 Plan Digest 创建绑定。

```sql
CREATE BINDING FROM HISTORY USING PLAN DIGEST '4e3159169cc63c14b139a4e7d72eae1759875c9a9581f94bb2079aae961189cb';
Expand Down Expand Up @@ -309,7 +309,7 @@ SELECT @@LAST_PLAN_FROM_BINDING;

### 删除绑定

你可以根据 SQL 语句或者 `sql_digest` 删除绑定。
你可以根据 SQL 语句或者 SQL Digest 删除绑定。

#### 根据 SQL 语句删除绑定

Expand All @@ -335,15 +335,15 @@ explain SELECT * FROM t1,t2 WHERE t1.id = t2.id;

在这里 SESSION 作用域内被删除掉的绑定会屏蔽 GLOBAL 作用域内相应的绑定，优化器不会为 `SELECT` 语句添加 `sm_join(t1, t2)` hint，`explain` 给出的执行计划中最上层节点并不被 hint 固定为 MergeJoin，而是由优化器经过代价估算后自主进行选择。

#### 根据 `sql_digest` 删除绑定
#### 根据 SQL Digest 删除绑定

除了可以根据 SQL 语句删除对应的绑定以外，也可以根据 `sql_digest` 删除绑定：
你既可以根据 SQL 语句删除对应的绑定，也可以根据 SQL Digest 删除绑定。详细说明和更多示例参见 [`DROP [GLOBAL|SESSION] BINDING`](/sql-statements/sql-statement-drop-binding.md)。

```sql
DROP [GLOBAL | SESSION] BINDING FOR SQL DIGEST 'sql_digest';
DROP [GLOBAL | SESSION] BINDING FOR SQL DIGEST StringLiteralOrUserVariableList;
```

该语句用于在 GLOBAL 或者 SESSION 作用域内删除 `sql_digest` 对应的的执行计划绑定，在不指定作用域时默认作用域为 SESSION。你可以通过[查看绑定](#查看绑定)语句获取 `sql_digest`。
该语句用于在 GLOBAL 或者 SESSION 作用域内删除 SQL Digest 对应的的执行计划绑定，在不指定作用域时默认作用域为 SESSION。你可以通过[查看绑定](#查看绑定)语句获取 SQL Digest。

> **注意：**
>
Expand Down
180 changes: 160 additions & 20 deletions sql-statements/sql-statement-create-binding.md
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Original file line number Diff line number Diff line change
Expand Up @@ -17,21 +17,30 @@ aliases: ['/docs-cn/dev/sql-statements/sql-statement-create-binding/']
```ebnf+diagram
CreateBindingStmt ::=
'CREATE' GlobalScope 'BINDING' ( 'FOR' BindableStmt 'USING' BindableStmt
| 'FROM' 'HISTORY' 'USING' 'PLAN' 'DIGEST' PlanDigest )
| 'FROM' 'HISTORY' 'USING' 'PLAN' 'DIGEST' StringLiteralOrUserVariableList )
GlobalScope ::=
( 'GLOBAL' | 'SESSION' )?
BindableStmt ::=
( SelectStmt | UpdateStmt | InsertIntoStmt | ReplaceIntoStmt | DeleteStmt )
```
****
StringLiteralOrUserVariableList ::=
( StringLitOrUserVariable | StringLiteralOrUserVariableList ',' StringLitOrUserVariable )
StringLiteralOrUserVariable ::=
( stringLiteral | UserVariable )
```

## 示例

你可以根据 SQL 或历史执行计划创建绑定。

根据历史执行计划创建绑定时，你需要指定相应的 Plan Digest：

- 既可以通过字符串字面量来指定，也可以通过字符串类型的用户变量来指定。
- 可以通过指定多个 Plan Digest 来同时为多个语句创建绑定。此时你可以指定多个字符串，同时每个字符串也可以包含多个 digest，注意字符串之间和 digest 之间均需使用逗号隔开。

下面的示例演示如何根据 SQL 创建绑定。

{{< copyable "sql" >}}
Expand Down Expand Up @@ -139,34 +148,165 @@ EXPLAIN ANALYZE SELECT * FROM t1 WHERE b = 123;
下面的示例演示如何根据历史执行计划创建绑定。

```sql
mysql> CREATE TABLE t(id INT PRIMARY KEY , a INT, KEY(a));
Query OK, 0 rows affected (0.06 sec)
USE test;
CREATE TABLE t1(a INT, b INT, c INT, INDEX ia(a));
CREATE TABLE t2(a INT, b INT, c INT, INDEX ia(a));
INSERT INTO t1 SELECT * FROM t2 WHERE a = 1;
SELECT @@LAST_PLAN_FROM_BINDING;
UPDATE /*+ INL_JOIN(t2) */ t1, t2 SET t1.a = 1 WHERE t1.b = t2.a;
SELECT @@LAST_PLAN_FROM_BINDING;
DELETE /*+ HASH_JOIN(t1) */ t1 FROM t1 JOIN t2 WHERE t1.b = t2.a;
SELECT @@LAST_PLAN_FROM_BINDING;
SELECT * FROM t1 WHERE t1.a IN (SELECT a FROM t2);
SELECT @@LAST_PLAN_FROM_BINDING;
```

方法一：

```sql
SELECT query_sample_text, stmt_type, table_names, plan_digest FROM information_schema.statements_summary_history WHERE table_names LIKE '%test.t1%' AND stmt_type != 'CreateTable';
CREATE GLOBAL BINDING FROM HISTORY USING PLAN DIGEST 'e72819cf99932f63a548156dbf433adda60e10337e89dcaa8638b4caf16f64d8,c291edc36b2482738d3389d335f37efc76290be2930330fe5034c5f4c42eeb36,8dc146249484f4a6ab219bfe9effa6b7a18aeed3764d49b610da61ac347ab914,73b2dec866595688ea416675f88ccb3456eb8e7443a79cd816695b688e07ac6b';
```

方法二：

```sql
SELECT @digests:=GROUP_CONCAT(plan_digest) FROM information_schema.statements_summary_history WHERE table_names LIKE '%test.t1%' AND stmt_type != 'CreateTable';
CREATE GLOBAL BINDING FROM HISTORY USING PLAN DIGEST @digests;
```

```sql
SHOW GLOBAL BINDINGS;
INSERT INTO t1 SELECT * FROM t2 WHERE a = 1;
SELECT @@LAST_PLAN_FROM_BINDING;
UPDATE t1, t2 SET t1.a = 1 WHERE t1.b = t2.a;
SELECT @@LAST_PLAN_FROM_BINDING;
DELETE t1 FROM t1 JOIN t2 WHERE t1.b = t2.a;
SELECT @@LAST_PLAN_FROM_BINDING;
SELECT * FROM t1 WHERE t1.a IN (SELECT a FROM t2);
SELECT @@LAST_PLAN_FROM_BINDING;
```

```sql
> CREATE TABLE t1(a INT, b INT, c INT, INDEX ia(a));
Query OK, 0 rows affected (0.048 sec)

mysql> SELECT /*+ IGNORE_INDEX(t, a) */ * FROM t WHERE a = 1;
Empty set (0.01 sec)
> CREATE TABLE t2(a INT, b INT, c INT, INDEX ia(a));
Query OK, 0 rows affected (0.035 sec)

mysql> SELECT plan_digest FROM INFORMATION_SCHEMA.STATEMENTS_SUMMARY WHERE QUERY_SAMPLE_TEXT = 'SELECT /*+ IGNORE_INDEX(t, a) */ * FROM t WHERE a = 1';
+------------------------------------------------------------------+
| plan_digest |
+------------------------------------------------------------------+
| 4e3159169cc63c14b139a4e7d72eae1759875c9a9581f94bb2079aae961189cb |
+------------------------------------------------------------------+
1 row in set (0.01 sec)
> INSERT INTO t1 SELECT * FROM t2 WHERE a = 1;
Query OK, 0 rows affected (0.002 sec)
Records: 0 Duplicates: 0 Warnings: 0

mysql> CREATE BINDING FROM HISTORY USING PLAN DIGEST '4e3159169cc63c14b139a4e7d72eae1759875c9a9581f94bb2079aae961189cb';
Query OK, 0 rows affected (0.02 sec)
> SELECT @@LAST_PLAN_FROM_BINDING;
+--------------------------+
| @@LAST_PLAN_FROM_BINDING |
+--------------------------+
| 0 |
+--------------------------+
1 row in set (0.001 sec)

mysql> SELECT * FROM t WHERE a = 1;
Empty set (0.01 sec)
> UPDATE /*+ INL_JOIN(t2) */ t1, t2 SET t1.a = 1 WHERE t1.b = t2.a;
Query OK, 0 rows affected (0.005 sec)
Rows matched: 0 Changed: 0 Warnings: 0

mysql> SELECT @@LAST_PLAN_FROM_BINDING;
> SELECT @@LAST_PLAN_FROM_BINDING;
+--------------------------+
| @@LAST_PLAN_FROM_BINDING |
+--------------------------+
| 0 |
+--------------------------+
1 row in set (0.000 sec)

> DELETE /*+ HASH_JOIN(t1) */ t1 FROM t1 JOIN t2 WHERE t1.b = t2.a;
Query OK, 0 rows affected (0.003 sec)

> SELECT @@LAST_PLAN_FROM_BINDING;
+--------------------------+
| @@LAST_PLAN_FROM_BINDING |
+--------------------------+
| 0 |
+--------------------------+
1 row in set (0.000 sec)

> SELECT * FROM t1 WHERE t1.a IN (SELECT a FROM t2);
Empty set (0.002 sec)

> SELECT @@LAST_PLAN_FROM_BINDING;
+--------------------------+
| @@LAST_PLAN_FROM_BINDING |
+--------------------------+
| 0 |
+--------------------------+
1 row in set (0.001 sec)

> SELECT @digests:=GROUP_CONCAT(plan_digest) FROM information_schema.statements_summary_history WHERE table_names LIKE '%test.t1%' AND stmt_type != 'CreateTable';
+---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| @digests:=GROUP_CONCAT(plan_digest) |
+---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| 73b2dec866595688ea416675f88ccb3456eb8e7443a79cd816695b688e07ac6b,8dc146249484f4a6ab219bfe9effa6b7a18aeed3764d49b610da61ac347ab914,c291edc36b2482738d3389d335f37efc76290be2930330fe5034c5f4c42eeb36,e72819cf99932f63a548156dbf433adda60e10337e89dcaa8638b4caf16f64d8 |
+---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
1 row in set (0.001 sec)

> CREATE GLOBAL BINDING FROM HISTORY USING PLAN DIGEST @digests;
Query OK, 0 rows affected (0.060 sec)

> SHOW GLOBAL BINDINGS;
+----------------------------------------------------------------------------------------------+----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+------------+---------+-------------------------+-------------------------+---------+-----------------+---------+------------------------------------------------------------------+------------------------------------------------------------------+
| Original_sql | Bind_sql | Default_db | Status | Create_time | Update_time | Charset | Collation | Source | Sql_digest | Plan_digest |
+----------------------------------------------------------------------------------------------+----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+------------+---------+-------------------------+-------------------------+---------+-----------------+---------+------------------------------------------------------------------+------------------------------------------------------------------+
| insert into `test` . `t1` select * from `test` . `t2` where `a` = ? | INSERT INTO `test`.`t1` SELECT /*+ use_index(@`sel_1` `test`.`t2` `ia`) no_order_index(@`sel_1` `test`.`t2` `ia`)*/ * FROM `test`.`t2` WHERE `a` = 1 | test | enabled | 2024-08-11 05:27:19.669 | 2024-08-11 05:27:19.669 | utf8 | utf8_general_ci | history | bd23e6af17e7b77b25383e50e258f0dece18583d19772f08caacb2021945a300 | e72819cf99932f63a548156dbf433adda60e10337e89dcaa8638b4caf16f64d8 |
| update ( `test` . `t1` ) join `test` . `t2` set `t1` . `a` = ? where `t1` . `b` = `t2` . `a` | UPDATE /*+ inl_join(`test`.`t2`) use_index(@`upd_1` `test`.`t1` ) use_index(@`upd_1` `test`.`t2` `ia`) no_order_index(@`upd_1` `test`.`t2` `ia`)*/ (`test`.`t1`) JOIN `test`.`t2` SET `t1`.`a`=1 WHERE `t1`.`b` = `t2`.`a` | test | enabled | 2024-08-11 05:27:19.667 | 2024-08-11 05:27:19.667 | utf8 | utf8_general_ci | history | 987e91af17eb40e36fecfc0634cce0b6a736de02bb009091810f932804fc02e9 | c291edc36b2482738d3389d335f37efc76290be2930330fe5034c5f4c42eeb36 |
| delete `test` . `t1` from `test` . `t1` join `test` . `t2` where `t1` . `b` = `t2` . `a` | DELETE /*+ hash_join_build(`test`.`t2`) use_index(@`del_1` `test`.`t1` ) use_index(@`del_1` `test`.`t2` )*/ `test`.`t1` FROM `test`.`t1` JOIN `test`.`t2` WHERE `t1`.`b` = `t2`.`a` | test | enabled | 2024-08-11 05:27:19.664 | 2024-08-11 05:27:19.664 | utf8 | utf8_general_ci | history | 70ef3d442d95c51020a76c7c86a3ab674258606d4dd24bbd16ac6f69d87a4316 | 8dc146249484f4a6ab219bfe9effa6b7a18aeed3764d49b610da61ac347ab914 |
| select * from `test` . `t1` where `t1` . `a` in ( select `a` from `test` . `t2` ) | SELECT /*+ use_index(@`sel_1` `test`.`t1` ) stream_agg(@`sel_2`) use_index(@`sel_2` `test`.`t2` `ia`) order_index(@`sel_2` `test`.`t2` `ia`) agg_to_cop(@`sel_2`)*/ * FROM `test`.`t1` WHERE `t1`.`a` IN (SELECT `a` FROM `test`.`t2`) | test | enabled | 2024-08-11 05:27:19.649 | 2024-08-11 05:27:19.649 | utf8 | utf8_general_ci | history | b58508a5e29d7889adf98cad50343d7a575fd32ad55dbdaa88e14ecde54f3d93 | 73b2dec866595688ea416675f88ccb3456eb8e7443a79cd816695b688e07ac6b |
+----------------------------------------------------------------------------------------------+----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+------------+---------+-------------------------+-------------------------+---------+-----------------+---------+------------------------------------------------------------------+------------------------------------------------------------------+
4 rows in set (0.001 sec)

> INSERT INTO t1 SELECT * FROM t2 WHERE a = 1;
Query OK, 0 rows affected (0.002 sec)
Records: 0 Duplicates: 0 Warnings: 0

> SELECT @@LAST_PLAN_FROM_BINDING;
+--------------------------+
| @@LAST_PLAN_FROM_BINDING |
+--------------------------+
| 1 |
+--------------------------+
1 row in set (0.01 sec)
1 row in set (0.000 sec)

> UPDATE t1, t2 SET t1.a = 1 WHERE t1.b = t2.a;
Query OK, 0 rows affected (0.002 sec)
Rows matched: 0 Changed: 0 Warnings: 0

> SELECT @@LAST_PLAN_FROM_BINDING;
+--------------------------+
| @@LAST_PLAN_FROM_BINDING |
+--------------------------+
| 1 |
+--------------------------+
1 row in set (0.000 sec)

> DELETE t1 FROM t1 JOIN t2 WHERE t1.b = t2.a;
Query OK, 0 rows affected (0.002 sec)

> SELECT @@LAST_PLAN_FROM_BINDING;
+--------------------------+
| @@LAST_PLAN_FROM_BINDING |
+--------------------------+
| 1 |
+--------------------------+
1 row in set (0.000 sec)

> SELECT * FROM t1 WHERE t1.a IN (SELECT a FROM t2);
Empty set (0.002 sec)

> SELECT @@LAST_PLAN_FROM_BINDING;
+--------------------------+
| @@LAST_PLAN_FROM_BINDING |
+--------------------------+
| 1 |
+--------------------------+
1 row in set (0.002 sec)
```

## MySQL 兼容性
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