*: upgrade tidb_auto_analyze_partition_batch_size default value (#19817…

…) (#20337)

releases/release-8.2.0.md

@@ -177,6 +177,7 @@ Quick access: [Quick start](https://docs.pingcap.com/tidb/v8.2/quick-start-with-
 |--------|------------------------------|------|
 | [`tidb_analyze_distsql_scan_concurrency`](/system-variables.md#tidb_analyze_distsql_scan_concurrency-new-in-v760) | Modified  |  Changes the minimum value from `1` to `0`. When you set it to `0`, TiDB adaptively adjusts the concurrency of the `scan` operation when executing the `ANALYZE` operation based on the cluster size.|
 | [`tidb_analyze_skip_column_types`](/system-variables.md#tidb_analyze_skip_column_types-new-in-v720) | Modified  | Starting from v8.2.0, TiDB does not collect columns of `MEDIUMTEXT` and `LONGTEXT` types by default to avoid potential OOM risks.|
+| [`tidb_auto_analyze_partition_batch_size`](/system-variables.md#tidb_auto_analyze_partition_batch_size-new-in-v640) | Modified | Changes the default value from `128` to `8192` to reduce the impact of automatic statistics collection on the performance of TiDB clusters. Changes the value range from `[1, 1024]` to `[1, 8192]`. |
 | [`tidb_enable_historical_stats`](/system-variables.md#tidb_enable_historical_stats) | Modified   |  Changes the default value from `ON` to `OFF`, which turns off historical statistics to avoid potential stability issues.|
 | [`tidb_executor_concurrency`](/system-variables.md#tidb_executor_concurrency-new-in-v50) | Modified | Adds support for setting the concurrency of the `sort` operator. |
 | [`tidb_sysproc_scan_concurrency`](/system-variables.md#tidb_sysproc_scan_concurrency-new-in-v650) | Modified    | Changes the minimum value from `1` to `0`. When you set it to `0`, TiDB adaptively adjusts the concurrency of `scan` operations performed when executing internal SQL statements based on the cluster size.|

system-variables.md

@@ -1229,8 +1229,8 @@ mysql> SELECT job_info FROM mysql.analyze_jobs ORDER BY end_time DESC LIMIT 1;
 - Scope: GLOBAL
 - Persists to cluster: Yes
 - Applies to hint [SET_VAR](/optimizer-hints.md#set_varvar_namevar_value): No
-- Default value: `128`. Before v7.6.0, the default value is `1`.
-- Range: `[1, 1024]`
+- Default value: `8192`. Before v7.6.0, the default value is `1`. For versions from v7.6.0 to v8.1.x, the default value is `128`. Starting from v8.2.0, the default value changes to `8192`.
+- Range: `[1, 8192]`. Before v8.2.0, the value range is `[1, 1024]`.
 - This variable specifies the number of partitions that TiDB [automatically analyzes](/statistics.md#automatic-update) when analyzing a partitioned table (which means automatically collecting statistics on a partitioned table).
 - If the value of this variable is smaller than the number of partitions, TiDB automatically analyzes all partitions of the partitioned table in multiple batches. If the value of this variable is greater than or equal to the number of partitions, TiDB analyzes all partitions of the partitioned table at the same time.
 - If the number of partitions of a partitioned table is far greater than this variable value and the auto-analyze takes a long time, you can increase the value of this variable to reduce the time consumption.