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revise expressions pushed down #8684

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merged 14 commits into from
Mar 24, 2022
Merged

revise expressions pushed down #8684

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c5f262e
revise
Yisaer Mar 16, 2022
96d2e65
address the comment
Yisaer Mar 17, 2022
b8941d4
editorial review
en-jin19 Mar 21, 2022
12e640e
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en-jin19 Mar 22, 2022
7e0bb3a
update descriptions
en-jin19 Mar 22, 2022
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Merge branch 'revise_push' of https://github.com/Yisaer/docs-cn into …
en-jin19 Mar 22, 2022
c8ad7af
add variable
Yisaer Mar 23, 2022
9b5b0a7
Merge branch 'revise_push' of https://github.com/Yisaer/docs-cn into …
Yisaer Mar 23, 2022
61e9001
Update functions-and-operators/expressions-pushed-down.md
Yisaer Mar 23, 2022
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Yisaer Mar 23, 2022
aa5f658
revise formats and descriptions
en-jin19 Mar 23, 2022
8191dee
add version info to the configuration
en-jin19 Mar 23, 2022
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en-jin19 Mar 24, 2022
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Update system-variables.md
TomShawn Mar 24, 2022
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address the comment 
Signed-off-by: yisaer <disxiaofei@163.com>
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@Yisaer
Yisaer committed Mar 17, 2022
commit 96d2e659eb7a16842627624f081314c659b95349
8 changes: 7 additions & 1 deletion functions-and-operators/expressions-pushed-down.md
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Expand Up @@ -18,7 +18,6 @@ aliases: ['/docs-cn/dev/functions-and-operators/expressions-pushed-down/','/docs
| [控制流运算](/functions-and-operators/control-flow-functions.md) | [`CASE`](https://dev.mysql.com/doc/refman/5.7/en/flow-control-functions.html#operator_case), [`IF()`](https://dev.mysql.com/doc/refman/5.7/en/flow-control-functions.html#function_if), [`IFNULL()`](https://dev.mysql.com/doc/refman/5.7/en/flow-control-functions.html#function_ifnull) |
| [JSON运算](/functions-and-operators/json-functions.md) | [JSON_TYPE(json_val)][json_type],<br/> [JSON_EXTRACT(json_doc, path[, path] ...)][json_extract],<br/> [JSON_OBJECT(key, val[, key, val] ...)][json_object],<br/> [JSON_ARRAY([val[, val] ...])][json_array],<br/> [JSON_MERGE(json_doc, json_doc[, json_doc] ...)][json_merge],<br/> [JSON_SET(json_doc, path, val[, path, val] ...)][json_set],<br/> [JSON_INSERT(json_doc, path, val[, path, val] ...)][json_insert],<br/> [JSON_REPLACE(json_doc, path, val[, path, val] ...)][json_replace],<br/> [JSON_REMOVE(json_doc, path[, path] ...)][json_remove] |
| [日期运算](/functions-and-operators/date-and-time-functions.md) | [`DATE_FORMAT()`](https://dev.mysql.com/doc/refman/5.7/en/date-and-time-functions.html#function_date-format) |
| [数据类型](/data-type-overview.md) | [BIT](/data-type-numeric.md#bit-类型), [ENUM](/data-type-string.md#enum-类型) |

## 禁止特定表达式下推

Expand Down Expand Up @@ -51,6 +50,13 @@ tidb> desc mysql.expr_pushdown_blacklist;
>
> `tidb` 是一种特殊的 store_type，其含义是 TiDB 内存表，比如：`PERFORMANCE_SCHEMA.events_statements_summary_by_digest`，属于系统表的一种，非特殊情况不用考虑这种存储引擎。

当数据列的计算过程由于下推而出现异常时，可通过黑名单功能禁止其下推来快速恢复业务。具体而言，你可以将数据列类型加入黑名单 `mysql.expr_pushdown_blacklist` 中，以禁止列下推, 目前仅支持 `ENUM` 和 `BIT`。

```sql
mysql> insert into mysql.expr_pushdown_blacklist values('bit', 'tikv','');
Query OK, 1 row affected (0.01 sec)
```

### 加入黑名单

执行以下步骤，可将一个或多个函数或运算符加入黑名单：
Expand Down