system-variables: update from generated source

releases/release-5.3.0.md

@@ -32,8 +32,8 @@ In v5.3, the key new features or improvements are as follows:
 | :---------- | :----------- | :----------- |
 | [`tidb_enable_noop_functions`](/system-variables.md#tidb_enable_noop_functions-new-in-v40) | Modified |  Temporary tables are now supported by TiDB so `CREATE TEMPORARY TABLE` and `DROP TEMPORARY TABLE` no longer require enabling `tidb_enable_noop_functions`. |
 | [`tidb_enable_pseudo_for_outdated_stats`](/system-variables.md#tidb_enable_pseudo_for_outdated_stats-new-in-v530) | Newly added | Controls the behavior of the optimizer when the statistics on a table expire. The default value is `ON`. When the number of modified rows in the table is greater than 80% of the total rows (This ratio can be adjusted by the configuration [`pseudo-estimate-ratio`](/tidb-configuration-file.md#pseudo-estimate-ratio)), the optimizer considers that the statistics other than the total number of rows are no longer reliable and use pseudo statistics instead. When you set the value as `OFF`, even if the statistics expire, the optimizer still uses them. |
-|[`tidb_enable_tso_follower_proxy`](/system-variables.md#tidb_enable_tso_follower_proxy-new-in-v53) | Newly added  | Determines whether to enable or disable the TSO Follower Proxy feature. The default value is `OFF`, which means the TSO Follower Proxy feature is disabled. At this time, TiDB only gets TSO from PD leader. When this feature is enabled, TiDB evenly sends the requests to all PD nodes when acquiring TSO. The PD follower then forwards the TSO requests to reduce the CPU pressure of PD leader. |
-|[`tidb_tso_client_batch_max_wait_time`](/system-variables.md#tidb_tso_client_batch_max_wait_time-new-in-v53) | Newly added |  Sets the maximum waiting time for a batch saving operation when TiDB requests TSO from PD. The default value is `0`, which means no additional waiting. |
+|[`tidb_enable_tso_follower_proxy`](/system-variables.md#tidb_enable_tso_follower_proxy-new-in-v530) | Newly added  | Determines whether to enable or disable the TSO Follower Proxy feature. The default value is `OFF`, which means the TSO Follower Proxy feature is disabled. At this time, TiDB only gets TSO from PD leader. When this feature is enabled, TiDB evenly sends the requests to all PD nodes when acquiring TSO. The PD follower then forwards the TSO requests to reduce the CPU pressure of PD leader. |
+|[`tidb_tso_client_batch_max_wait_time`](/system-variables.md#tidb_tso_client_batch_max_wait_time-new-in-v530) | Newly added |  Sets the maximum waiting time for a batch saving operation when TiDB requests TSO from PD. The default value is `0`, which means no additional waiting. |
 | [`tidb_tmp_table_max_size`](/system-variables.md#tidb_tmp_table_max_size-new-in-v530) | Newly added  | Limits the maximum size of a single [temporary table](/temporary-tables.md). If the temporary table exceeds this size, an error will occur. |
 
 ### Configuration file parameters
@@ -134,19 +134,19 @@ In v5.3, the key new features or improvements are as follows:
 
     TiDB optimizes its timestamp processing flow and reduces the timestamp processing load of PD by enabling PD Follower Proxy and modifying the batch waiting time required when the PD client requests TSO in batches. This helps improve the overall scalability of the system.
 
-    - Support enabling or disabling PD Follower Proxy through the system variable [`tidb_enable_tso_follower_proxy`](/system-variables.md#tidb_enable_tso_follower_proxy-new-in-v53). Suppose that the TSO requests load of PD is too high. In this case, enabling PD follower proxy can batch forward the TSO requests collected during the request cycle on followers to the leader nodes. This solution can effectively reduce the number of direct interactions between clients and leaders, reduce the pressure of the load on leaders, and improve the overall performance of TiDB. 
+    - Support enabling or disabling PD Follower Proxy through the system variable [`tidb_enable_tso_follower_proxy`](/system-variables.md#tidb_enable_tso_follower_proxy-new-in-v530). Suppose that the TSO requests load of PD is too high. In this case, enabling PD follower proxy can batch forward the TSO requests collected during the request cycle on followers to the leader nodes. This solution can effectively reduce the number of direct interactions between clients and leaders, reduce the pressure of the load on leaders, and improve the overall performance of TiDB. 
 
     > **Note:**
     >
     > When the number of clients is small and the PD leader CPU load is not full, it is NOT recommended to enable PD Follower Proxy.
 
-    - Support using the system variable [`tidb_tso_client_batch_max_wait_time`](/system-variables.md#tidb_tso_client_batch_max_wait_time-new-in-v53) to set the maximum waiting time needed for the PD client to batch request TSO. The unit of this time is milliseconds. In case that PD has a high TSO requests load, you can reduce the load and improve the throughput by increasing the waiting time to get a larger batch size.
+    - Support using the system variable [`tidb_tso_client_batch_max_wait_time`](/system-variables.md#tidb_tso_client_batch_max_wait_time-new-in-v530) to set the maximum waiting time needed for the PD client to batch request TSO. The unit of this time is milliseconds. In case that PD has a high TSO requests load, you can reduce the load and improve the throughput by increasing the waiting time to get a larger batch size.
 
     > **Note:**
     >
     > When the TSO request load is not high, it is NOT recommended to modify this variable value.
 
-    [User document](/system-variables.md#tidb_tso_client_batch_max_wait_time-new-in-v53), [#3149](https://github.com/tikv/pd/issues/3149)
+    [User document](/system-variables.md#tidb_tso_client_batch_max_wait_time-new-in-v530), [#3149](https://github.com/tikv/pd/issues/3149)
 
 ### Stability
 

system-variables.md

@@ -294,10 +294,10 @@ This variable is an alias for `last_insert_id`.
 >
 > Unlike in MySQL, the `max_execution_time` system variable currently works on all kinds of statements in TiDB, not only restricted to the `SELECT` statement. The precision of the timeout value is roughly 100ms. This means the statement might not be terminated in accurate milliseconds as you specify.
 
-### placement_checks
+### placement_checks <span class="version-mark">New in v5.3.0</span>
 
 - Scope: SESSION | GLOBAL
-- Default value: ON
+- Default value: `ON`
 - This variable controls whether DDL statements validate [Placement Rules in SQL](/placement-rules-in-sql.md).
 - It is intended to be used by logical dump/restore tools to ensure that tables can always be created even if placement rules are violated. This is similar to how mysqldump writes `SET FOREIGN_KEY_CHECKS=0;` to the start of every dump file.
 
@@ -411,6 +411,7 @@ This variable is an alias for `last_insert_id`.
 ### tidb_allow_function_for_expression_index <span class="version-mark">New in v5.2.0</span>
 
 - Scope: NONE
+- Default value: `lower, md5, reverse, upper, vitess_hash`
 - This variable is used to show the functions that are allowed to be used for creating expression indexes.
 
 ### tidb_allow_mpp <span class="version-mark">New in v5.0</span>
@@ -845,14 +846,14 @@ Query OK, 0 rows affected (0.09 sec)
 - Default value: `ON`
 - This variable is used to dynamically control whether the telemetry collection in TiDB is enabled. By setting the value to `OFF`, the telemetry collection is disabled. If the [`enable-telemetry`](/tidb-configuration-file.md#enable-telemetry-new-in-v402) TiDB configuration item is set to `false` on all TiDB instances, the telemetry collection is always disabled and this system variable will not take effect. See [Telemetry](/telemetry.md) for details.
 
-### tidb_enable_tso_follower_proxy <span class="version-mark">New in v5.3</span>
+### tidb_enable_tso_follower_proxy <span class="version-mark">New in v5.3.0</span>
 
 - Scope: GLOBAL
 - Default value: `OFF`
 - This variable is used to enable the TSO Follower Proxy feature. When the value is `OFF`, TiDB only gets TSO from the PD leader. After this feature is enabled, TiDB gets TSO by evenly sending requests to all PD nodes and forwarding TSO requests through PD followers. This helps reduce the CPU pressure of PD leader.
 - Scenarios for enabling TSO Follower Proxy:
     * Due to the high pressure of TSO requests, the CPU of the PD leader reaches a bottleneck, which causes high latency of TSO RPC requests.
-    * The TiDB cluster has many TiDB instances, and increasing the value of [`tidb_tso_client_batch_max_wait_time`](#tidb_tso_client_batch_max_wait_time-new-in-v53) cannot alleviate the high latency issue of TSO RPC requests.
+    * The TiDB cluster has many TiDB instances, and increasing the value of [`tidb_tso_client_batch_max_wait_time`](#tidb_tso_client_batch_max_wait_time-new-in-v530) cannot alleviate the high latency issue of TSO RPC requests.
 
 > **Note:**
 >
@@ -1130,10 +1131,11 @@ For a system upgraded to v5.0 from an earlier version, if you have not modified
 - Default value: `tikv,tiflash,tidb`
 - This variable is used to set the storage engine list that TiDB can use when reading data.
 
-### tidb_log_file_max_days <span class="version-mark">New in v5.3</span>
+### tidb_log_file_max_days <span class="version-mark">New in v5.3.0</span>
 
 - Scope: SESSION
 - Default value: `0`
+- Range: `[0, 2147483647]`
 - This variable is used to adjust the maximum days of logger on the current TiDB instance. Its value defaults to the value of the [`max-days`](/tidb-configuration-file.md#max-days) configuration in the configuration file. Changing the variable value only affects the current TiDB instance. After TiDB is restarted, the variable value is reset and the configuration value is not affected.
 
 ### tidb_low_resolution_tso
@@ -1553,7 +1555,7 @@ SET tidb_slow_log_threshold = 200;
 - Unit: Bytes
 - This variable is used to set the maximum size of a single [temporary table](/temporary-tables.md). Any temporary table with a size larger than this variable value causes error.
 
-### tidb_tso_client_batch_max_wait_time <span class="version-mark">New in v5.3</span>
+### tidb_tso_client_batch_max_wait_time <span class="version-mark">New in v5.3.0</span>
 
 - Scope: GLOBAL
 - Default value: `0`
@@ -1626,7 +1628,7 @@ SET tidb_slow_log_threshold = 200;
 ### timestamp
 
 - Scope: SESSION
-- Default value: ""
+- Default value: `0`
 - A non-empty value of this variable indicates the UNIX epoch that is used as the timestamp for `CURRENT_TIMESTAMP()`, `NOW()`, and other functions. This variable might be used in data restore or replication.
 
 ### transaction_isolation
@@ -1652,22 +1654,22 @@ This variable is an alias for `transaction_isolation`.
 - Default value: (string)
 - This variable returns additional details about the TiDB version. For example, 'TiDB Server (Apache License 2.0) Community Edition, MySQL 5.7 compatible'.
 
-### version_compile_os
+### version_compile_machine
 
 - Scope: NONE
 - Default value: (string)
-- This variable returns the name of the OS on which TiDB is running.
+- This variable returns the name of the CPU architecture on which TiDB is running.
 
-### version_compile_machine
+### version_compile_os
 
 - Scope: NONE
 - Default value: (string)
-- This variable returns the name of the CPU architecture on which TiDB is running.
+- This variable returns the name of the OS on which TiDB is running.
 
 ### wait_timeout
 
 - Scope: SESSION | GLOBAL
-- Default value: `0`
+- Default value: `28800`
 - Range: `[0, 31536000]`
 - Unit: Seconds
 - This variable controls the idle timeout of user sessions. A zero-value means unlimited.