Add/clarify SQL length limits (#16172) (#16228)

pingcap · Jan 22, 2024 · f63038e · f63038e
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diff --git a/dashboard/dashboard-slow-query.md b/dashboard/dashboard-slow-query.md
@@ -59,6 +59,10 @@ summary: 了解如何在 TiDB Dashboard 中查看慢查询。
 
 ### SQL
 
+>**注意：**
+>
+> 记录在 `Query` 中的查询的长度会受到 [`tidb_stmt_summary_max_sql_length`](/system-variables.md#tidb_stmt_summary_max_sql_length-从-v40-版本开始引入) 系统变量的限制。
+
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 ### 执行计划

diff --git a/information-schema/information-schema-slow-query.md b/information-schema/information-schema-slow-query.md
@@ -202,9 +202,9 @@ DESC SELECT COUNT(*) FROM CLUSTER_SLOW_QUERY WHERE user = 'u1';
 | id                         | estRows  | task      | access object            | operator info                                        |
 +----------------------------+----------+-----------+--------------------------+------------------------------------------------------+
 | StreamAgg_7                | 1.00     | root      |                          | funcs:count(1)->Column#75                            |
-| └─TableReader_13       | 10.00    | root      |                          | data:Selection_12                                    |
-|   └─Selection_12       | 10.00    | cop[tidb] |                          | eq(INFORMATION_SCHEMA.cluster_slow_query.user, "u1") |
-|     └─TableFullScan_11 | 10000.00 | cop[tidb] | table:CLUSTER_SLOW_QUERY | keep order:false, stats:pseudo                       |
+| └─TableReader_13           | 10.00    | root      |                          | data:Selection_12                                    |
+|   └─Selection_12           | 10.00    | cop[tidb] |                          | eq(INFORMATION_SCHEMA.cluster_slow_query.user, "u1") |
+|     └─TableFullScan_11     | 10000.00 | cop[tidb] | table:CLUSTER_SLOW_QUERY | keep order:false, stats:pseudo                       |
 +----------------------------+----------+-----------+--------------------------+------------------------------------------------------+
 4 rows in set (0.00 sec)
 ```

diff --git a/system-variables.md b/system-variables.md
@@ -4462,7 +4462,7 @@ Query OK, 0 rows affected, 1 warning (0.00 sec)
 - 类型：整数型
 - 默认值：`4096`
 - 范围：`[0, 2147483647]`
-- 这个变量控制 [statement summary tables](/statement-summary-tables.md) 显示的 SQL 字符串长度。
+- 这个变量用来控制 [Statement Summary Tables](/statement-summary-tables.md)、[`SLOW_QUERY`](/information-schema/information-schema-slow-query.md) 表和 [TiDB Dashboard](/dashboard/dashboard-intro.md) 中显示的 SQL 字符串长度。
 
 ### `tidb_stmt_summary_max_stmt_count` <span class="version-mark">从 v4.0 版本开始引入</span>