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Change the default value of feedback-probability #4331

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Sep 8, 2020
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Change the default value of feedback-probability #4331

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统计信息：修正 `feedback-probability` 的默认值说明
winoros Aug 25, 2020
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Update statistics.md
TomShawn Aug 26, 2020
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Merge branch 'master' into feedback-default
TomShawn Sep 2, 2020
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Update statistics.md
winoros Sep 8, 2020
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Apply suggestions from code review
TomShawn Sep 8, 2020
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Merge branch 'master' into feedback-default
ti-srebot Sep 8, 2020
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6 changes: 5 additions & 1 deletion statistics.md
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Expand Up @@ -126,7 +126,11 @@ ANALYZE INCREMENTAL TABLE TableName PARTITION PartitionNameList INDEX [IndexName

当某个表 `tbl` 的修改行数与总行数的比值大于 `tidb_auto_analyze_ratio`，并且当前时间在 `tidb_auto_analyze_start_time` 和 `tidb_auto_analyze_end_time` 之间时，TiDB 会在后台执行 `ANALYZE TABLE tbl` 语句自动更新这个表的统计信息。

在查询语句执行时，TiDB 会以 `feedback-probability` 的概率收集反馈信息，并将其用于更新直方图和 Count-Min Sketch。`feedback-probability` 可通过配置文件修改，其默认值是 `0.0`。
在查询语句执行时，TiDB 会以 `feedback-probability` 的概率收集反馈信息，并将其用于更新直方图和 Count-Min Sketch。可通过配置文件修改 `feedback-probability`，其默认值是 `0.05`。设置成 `0.0` 可以关闭这个功能。

> **注意：**
>
> 在配置文件中如果将 `feedback-probability` 设置为 `0` 会导致设置失败并报错。需要设置成 `0.0` 才可以关闭 `feedback-probability`。

### 控制 ANALYZE 并发度

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