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faq: update an outdated sentence (#16739) (#16750)
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ti-chi-bot authored Mar 13, 2024
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Expand Up @@ -229,9 +229,11 @@ You can combine the above two parameters with the DML of TiDB to use them. For e

## What's the trigger strategy for `auto analyze` in TiDB?

When the number of rows in a new table reaches 1000, and the ratio (the number of modified rows / the current total number of rows) is larger than `tidb_auto_analyze_ratio`, the [`ANALYZE`](/sql-statements/sql-statement-analyze-table.md) statement is automatically triggered. The default value of `tidb_auto_analyze_ratio` is `0.5`, indicating that this feature is enabled by default. To ensure safety, its minimum value is `0.3` when the feature is enabled, and it must be smaller than `pseudo-estimate-ratio` whose default value is `0.8`; otherwise pseudo statistics will be used for a period of time. It is recommended to set `tidb_auto_analyze_ratio` to `0.5`.
When the number of rows in a table or a single partition of a partitioned table reaches 1000, and the ratio (the number of modified rows / the current total number of rows) of the table or partition is larger than [`tidb_auto_analyze_ratio`](/system-variables.md#tidb_auto_analyze_ratio), the [`ANALYZE`](/sql-statements/sql-statement-analyze-table.md) statement is automatically triggered.

To disable `auto analyze`, use the system variable `tidb_enable_auto_analyze`.
The default value of the `tidb_auto_analyze_ratio` system variable is `0.5`, indicating that this feature is enabled by default. It is not recommended to set the value of `tidb_auto_analyze_ratio` to be larger than or equal to [`pseudo-estimate-ratio`](/tidb-configuration-file.md#pseudo-estimate-ratio) (the default value is `0.8`), otherwise the optimizer might use pseudo statistics. TiDB v5.3.0 introduces the [`tidb_enable_pseudo_for_outdated_stats`](/system-variables.md#tidb_enable_pseudo_for_outdated_stats-new-in-v530) variable, and when you set it to `OFF`, pseudo statistics are not used even if the statistics are outdated.

To disable `auto analyze`, use the system variable [`tidb_enable_auto_analyze`](/system-variables.md#tidb_enable_auto_analyze-new-in-v610).

## Can I use optimizer hints to override the optimizer behavior?

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