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update descriptions of expressions supported to be pushed down #8761

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Mar 25, 2022
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update descriptions of expressions supported to be pushed down #8761

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a4a2df9
update descriptions of expressions supported to be pushed down
en-jin19 Mar 24, 2022
d3084e3
delete the duplicated item
en-jin19 Mar 25, 2022
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6 changes: 3 additions & 3 deletions functions-and-operators/expressions-pushed-down.md
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Expand Up @@ -52,18 +52,18 @@ tidb> desc mysql.expr_pushdown_blacklist;

### 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：
执行以下步骤，可将一个或多[函数名、运算符名](#已支持下推的表达式列表)或数据类型（**仅限** [`ENUM` 类型](/data-type-string.md#enum-类型) 和 [`BIT` 类型](/data-type-numeric.md#bit-类型)）加入黑名单：

1. 向 `mysql.expr_pushdown_blacklist` 插入以下内容：

- 希望禁止下推的[函数名、运算符名](#已支持下推的表达式列表)或数据类型（**仅限** [`ENUM` 类型](/data-type-string.md#enum-类型) 和 [`BIT` 类型](/data-type-numeric.md#bit-类型)）
- 希望禁止下推的函数名、运算符名或数据类型
- 希望禁止下推的存储引擎

2. 执行 `admin reload expr_pushdown_blacklist;`。

### 移出黑名单

执行以下步骤，可将一个或多个函数及运算符移出黑名单：
执行以下步骤，可将一个或多个函数名、运算符名或数据类型移出黑名单：

1. 从 `mysql.expr_pushdown_blacklist` 表中删除对应的函数名、运算符名或数据类型。
2. 执行 `admin reload expr_pushdown_blacklist;`。
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6 changes: 6 additions & 0 deletions system-variables.md
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Expand Up @@ -1552,6 +1552,12 @@ set tidb_slow_log_threshold = 200;
- 范围：`[0, 9223372036854775807]`
- 这个变量用于限制 TiDB 同时向 TiKV 发送的请求的最大数量，0 表示没有限制。

### `tidb_sysdate_is_now`（从 v6.0.0 版本开始引入）
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- 作用域：SESSION | GLOBAL
- 默认值：`OFF`
- 这个变量用于控制 `SYSDATE` 函数能否替换为 `NOW` 函数，其效果与 MYSQL 中的 [`sysdate-is-now`](https://dev.mysql.com/doc/refman/8.0/en/server-options.html#option_mysqld_sysdate-is-now) 一致。

### `tidb_table_cache_lease`（从 v6.0.0 版本开始引入）

- 作用域：GLOBAL
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