From ea31a725c8ddb0abc2a1d9a1f65a5062c8174ae5 Mon Sep 17 00:00:00 2001 From: shichun-0415 Date: Tue, 27 Sep 2022 18:28:56 +0800 Subject: [PATCH 1/4] add 6 system variables introduced in 6.3 but have no user doc --- system-variables.md | 64 +++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 64 insertions(+) diff --git a/system-variables.md b/system-variables.md index a2068d9d2230c..098aa7ca36cff 100644 --- a/system-variables.md +++ b/system-variables.md @@ -909,6 +909,18 @@ MPP is a distributed computing framework provided by the TiFlash engine, which a - Range: `[0, 9223372036854775807]` - This variable is used to set the number of retries when the DDL operation fails. When the number of retries exceeds the parameter value, the wrong DDL operation is canceled. +### `tidb_ddl_flashback_concurrency` New in v6.3.0 + +> **Warning:** +> +> The feature controlled by this variable is not fully functional in the current version. It is **not recommended** that you change the default value. + +- Scope: GLOBAL +- Persists to cluster: Yes +- Default value: `64` +- Range: `[1, 256]` +- This variable controls the concurrency of `flashback cluster`. + ### tidb_ddl_reorg_batch_size - Scope: GLOBAL @@ -1211,6 +1223,28 @@ MPP is a distributed computing framework provided by the TiFlash engine, which a - This variable is used to set whether to enable the statistics `Fast Analyze` feature. - If the statistics `Fast Analyze` feature is enabled, TiDB randomly samples about 10,000 rows of data as statistics. When the data is distributed unevenly or the data size is small, the statistics accuracy is low. This might lead to a non-optimal execution plan, for example, selecting a wrong index. If the execution time of the regular `Analyze` statement is acceptable, it is recommended to disable the `Fast Analyze` feature. +### `tidb_enable_foreign_key` New in v6.3.0 + +> **Warning:** +> +> The feature controlled by this variable is not fully functional in the current version. It is **not recommended** that you change the default value. + +- Scope: GLOBAL +- Persists to cluster: Yes +- Default value: `OFF` +- This variable controls whether to enable the `FOREIGN KEY` feature. + +### `tidb_enable_general_plan_cache` New in v6.3.0 + +> **Warning:** +> +> The feature controlled by this variable is not fully functional in the current version. It is **not recommended** that you change the default value. + +- Scope: SESSION | GLOBAL +- Persists to cluster: Yes +- Default value: `OFF` +- This variable controls whether to enable the General Plan Cache feature. + ### tidb_enable_index_merge New in v4.0 > **Note:** @@ -1320,6 +1354,13 @@ MPP is a distributed computing framework provided by the TiFlash engine, which a * When you use `SELECT` to read a `noop` variable, TiDB returns the `"variable *variable_name* has no effect in TiDB"` warning. - To check whether a TiDB instance has set and read the `noop` variable, you can use the `SELECT * FROM INFORMATION_SCHEMA.CLIENT_ERRORS_SUMMARY_GLOBAL;` statement. +### `tidb_enable_null_aware_anti_join` New in v6.3.0 + +- Scope: SESSION ｜GLOBAL +- Persists to cluster: Yes +- Default value: `OFF` +- This variable controls whether TiDB applies Null Aware Hash Join when ANTI JOIN is generated by subqueries led by special set operators `NOT IN` and `!= ALL`. + ### tidb_enable_outer_join_reorder New in v6.1.0 - Scope: SESSION | GLOBAL @@ -1496,6 +1537,17 @@ Query OK, 0 rows affected (0.09 sec) +### `tidb_enable_tiflash_read_for_write_stmt` 从 v6.3.0 版本开始引入 + +> **Warning:** +> +> The feature controlled by this variable is not fully functional in the current version. It is **not recommended** that you change the default value. + +- Scope: SESSION | GLOBAL +- Persists to cluster: Yes +- Default value: `OFF` +- This variable controls whether read requests in SQL write statements are pushed down to TiFlash. + ### tidb_enable_top_sql New in v5.4.0 @@ -1814,6 +1866,18 @@ For a system upgraded to v5.0 from an earlier version, if you have not modified +### `tidb_general_plan_cache_size` New in v6.3.0 + +> **Warning:** +> +> The feature controlled by this variable is not fully functional in the current version. It is **not recommended** that you change the default value. + +- Scope: SESSION | GLOBAL +- Persists to cluster: Yes +- Default value: `100` +- Range: `[1, 100000]` +- This variable controls the maximum number of execution plans that can be cached using General Plan Cache. + ### tidb_guarantee_linearizability New in v5.0 - Scope: SESSION | GLOBAL From c1dd6b3d7a5f75c2e56c5c117dc45590474cf783 Mon Sep 17 00:00:00 2001 From: shichun-0415 Date: Tue, 27 Sep 2022 18:32:13 +0800 Subject: [PATCH 2/4] fix Chinese --- system-variables.md | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/system-variables.md b/system-variables.md index 098aa7ca36cff..48ed73a89879a 100644 --- a/system-variables.md +++ b/system-variables.md @@ -1537,7 +1537,7 @@ Query OK, 0 rows affected (0.09 sec) -### `tidb_enable_tiflash_read_for_write_stmt` 从 v6.3.0 版本开始引入 +### `tidb_enable_tiflash_read_for_write_stmt` New in v6.3.0 > **Warning:** > From d517965842d7f73f667336b1fe8dc904cbc56b9e Mon Sep 17 00:00:00 2001 From: shichun-0415 <89768198+shichun-0415@users.noreply.github.com> Date: Wed, 28 Sep 2022 16:28:01 +0800 Subject: [PATCH 3/4] Apply suggestions from code review Co-authored-by: Grace Cai --- system-variables.md | 12 ++++++------ 1 file changed, 6 insertions(+), 6 deletions(-) diff --git a/system-variables.md b/system-variables.md index 48ed73a89879a..bd9168edffccd 100644 --- a/system-variables.md +++ b/system-variables.md @@ -913,7 +913,7 @@ MPP is a distributed computing framework provided by the TiFlash engine, which a > **Warning:** > -> The feature controlled by this variable is not fully functional in the current version. It is **not recommended** that you change the default value. +> The feature controlled by this variable is not fully functional in the current TiDB version. Do not change the default value. - Scope: GLOBAL - Persists to cluster: Yes @@ -1227,7 +1227,7 @@ MPP is a distributed computing framework provided by the TiFlash engine, which a > **Warning:** > -> The feature controlled by this variable is not fully functional in the current version. It is **not recommended** that you change the default value. +> The feature controlled by this variable is not fully functional in the current TiDB version. Do not change the default value. - Scope: GLOBAL - Persists to cluster: Yes @@ -1238,7 +1238,7 @@ MPP is a distributed computing framework provided by the TiFlash engine, which a > **Warning:** > -> The feature controlled by this variable is not fully functional in the current version. It is **not recommended** that you change the default value. +> The feature controlled by this variable is not fully functional in the current TiDB version. Do not change the default value. - Scope: SESSION | GLOBAL - Persists to cluster: Yes @@ -1541,7 +1541,7 @@ Query OK, 0 rows affected (0.09 sec) > **Warning:** > -> The feature controlled by this variable is not fully functional in the current version. It is **not recommended** that you change the default value. +> The feature controlled by this variable is not fully functional in the current TiDB version. Do not change the default value. - Scope: SESSION | GLOBAL - Persists to cluster: Yes @@ -1870,13 +1870,13 @@ For a system upgraded to v5.0 from an earlier version, if you have not modified > **Warning:** > -> The feature controlled by this variable is not fully functional in the current version. It is **not recommended** that you change the default value. +> The feature controlled by this variable is not fully functional in the current TiDB version. Do not change the default value. - Scope: SESSION | GLOBAL - Persists to cluster: Yes - Default value: `100` - Range: `[1, 100000]` -- This variable controls the maximum number of execution plans that can be cached using General Plan Cache. +- This variable controls the maximum number of execution plans that can be cached by General Plan Cache. ### tidb_guarantee_linearizability New in v5.0 From 3ed7f7803e3719de9ef8b7d682189db95dd5f3db Mon Sep 17 00:00:00 2001 From: shichun-0415 <89768198+shichun-0415@users.noreply.github.com> Date: Wed, 28 Sep 2022 19:28:25 +0800 Subject: [PATCH 4/4] Apply suggestions from code review Co-authored-by: Grace Cai --- system-variables.md | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/system-variables.md b/system-variables.md index bd9168edffccd..3eb05a08f1ae0 100644 --- a/system-variables.md +++ b/system-variables.md @@ -1546,7 +1546,7 @@ Query OK, 0 rows affected (0.09 sec) - Scope: SESSION | GLOBAL - Persists to cluster: Yes - Default value: `OFF` -- This variable controls whether read requests in SQL write statements are pushed down to TiFlash. +- This variable controls whether read requests in SQL write statements can be pushed down to TiFlash. ### tidb_enable_top_sql New in v5.4.0