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update some desc about auto-analyze #13540

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ti-chi-bot merged 5 commits into from
May 22, 2023
Merged

update some desc about auto-analyze #13540

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Update statistics.md
qiancai May 11, 2023
2c2028e
Update keywords.md
qiancai May 11, 2023
89f7a19
Update statistics.md
qiancai May 11, 2023
29bd493
Update statistics.md
qiancai May 22, 2023
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Merge remote-tracking branch 'upstream/master' into auto-analyze
qiancai May 22, 2023
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2 changes: 1 addition & 1 deletion keywords.md
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Expand Up @@ -671,6 +671,7 @@ The following list shows the keywords in TiDB. Reserved keywords are marked with
- THAN
- THEN (R)
- TIDB (R)
- TiDB_CURRENT_TSO (R)
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@qiancai qiancai May 11, 2023

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This change is from a comment in pingcap/docs-cn#13871 (comment).

- TIFLASH (R)
- TIKV_IMPORTER
- TIME
Expand All @@ -694,7 +695,6 @@ The following list shows the keywords in TiDB. Reserved keywords are marked with
- TTL_ENABLE
- TTL_JOB_INTERVAL
- TYPE
- TiDB_CURRENT_TSO (R)

<a id="U" class="letter" href="#U">U</a>

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20 changes: 19 additions & 1 deletion statistics.md
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Expand Up @@ -358,7 +358,19 @@ You can perform incremental collection using the following syntax.

### Automatic update

For the `INSERT`, `DELETE`, or `UPDATE` statements, TiDB automatically updates the number of rows and updated rows. TiDB persists this information regularly and the update cycle is 20 * `stats-lease`. The default value of `stats-lease` is `3s`. If you specify the value as `0`, it does not update automatically.
<CustomContent platform="tidb">

For the `INSERT`, `DELETE`, or `UPDATE` statements, TiDB automatically updates the number of rows and modified rows. TiDB persists this information regularly and the update cycle is 20 * [`stats-lease`](/tidb-configuration-file.md#stats-lease). The default value of `stats-lease` is `3s`. If you specify the value as `0`, TiDB stops updating statistics automatically.

</CustomContent>

<CustomContent platform="tidb-cloud">

For the `INSERT`, `DELETE`, or `UPDATE` statements, TiDB automatically updates the number of rows and modified rows. TiDB persists this information regularly and the update cycle is 20 * `stats-lease`. The default value of `stats-lease` is `3s`.

</CustomContent>

### Relevant system variables

Three system variables related to automatic update of statistics are as follows:

Expand All @@ -376,6 +388,12 @@ To avoid the situation that modifying a small amount of data on a small table fr
>
> Currently, the automatic update does not record the configuration items input at manual `ANALYZE`. Therefore, when you use the `WITH` syntax to control the collecting behavior of `ANALYZE`, you need to manually set scheduled tasks to collect statistics.

#### Disable automatic update

If you find that automatic update of statistics consumes excessive resources and affects online application operations, you can disable it using the [`tidb_enable_auto_analyze`](/system-variables.md#tidb_enable_auto_analyze-new-in-v610) system variable.

#### Terminate background `ANALYZE` tasks

Since TiDB v6.0, TiDB supports using the `KILL` statement to terminate an `ANALYZE` task running in the background. If you find that an `ANALYZE` task running in the background consumes a lot of resources and affects your application, you can terminate the `ANALYZE` task by taking the following steps:

1. Execute the following SQL statement:
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