tiflash: correct the default value of task_scheduler_active_set_soft_limit (#21137) #21145
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Summary of Changes
Hello @ti-chi-bot, I'm Gemini Code Assist1! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!
I've reviewed this automated cherry-pick PR. Its primary purpose is to update the documentation to include the release notes for TiDB 7.4.0 and correct the documented default value for the task_scheduler_active_set_soft_limit configuration parameter in TiFlash, ensuring the documentation reflects the actual behavior in the 7.4.0 release.
Highlights
- Documentation Update: Adds the complete release notes for TiDB 7.4.0, detailing new features, compatibility changes, improvements, and bug fixes for this version.
- TiFlash Configuration: Updates the TiFlash configuration documentation (
tiflash/tiflash-configuration.md) to include detailed descriptions of various parameters. - Parameter Default Value Correction: Specifically documents the change in the default value of the
task_scheduler_active_set_soft_limitconfiguration parameter in TiFlash fromvcpu * 0.25tovcpu * 2for v7.4.0.
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Code Review
This pull request introduces the release notes for TiDB 7.4.0 and updates the TiFlash configuration documentation, notably correcting the default value for task_scheduler_active_set_soft_limit. The most critical issue is a merge conflict in tiflash/tiflash-configuration.md that needs immediate attention. The new release notes file (releases/release-7.4.0.md) is comprehensive but has several areas for improvement regarding clarity, grammar, formatting, and adherence to the style guide. Specific suggestions are provided for these.
| @@ -39,6 +39,7 @@ This section introduces the configuration parameters of TiFlash. | |||
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| ### Configure the `tiflash.toml` file | |||
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This file contains a Git merge conflict marker <<<<<<< HEAD. This must be resolved before the pull request can be merged. Please remove the conflict markers and ensure the correct version of the content is retained.
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| * TiFlash supports the pipeline execution model (GA) [#6518](https://github.com/pingcap/tiflash/issues/6518) @[SeaRise](https://github.com/SeaRise) | ||
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| Starting from v7.2.0, TiFlash introduces a pipeline execution model. This model centrally manages all thread resources and schedules task execution uniformly, maximizing the utilization of thread resources while avoiding resource overuse. In v7.4.0, TiFlash improves the statistics of thread resource usage, and the pipeline execution model becomes a GA feature and is enabled by default. Since this feature is mutually dependent with the TiFlash resource control feature, TiDB v7.4.0 removes the variable `tidb_enable_tiflash_pipeline_model` used to control whether to enable the pipeline execution model in previous versions. Instead, you can enable or disable the pipeline execution model and the TiFlash resource control feature by configuring the TiFlash parameter `tidb_enable_resource_control`. |
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The TiFlash parameter mentioned here, tidb_enable_resource_control, seems incorrect. Based on the tiflash-configuration.md file, the TiFlash configuration parameter for resource control is enable_resource_control (likely under profiles.default). Please verify and use the correct TiFlash parameter name to avoid confusion.1
Style Guide References
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| ## Improvements | ||
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| + TiDB |
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The + prefix for section titles like + TiDB, + TiKV, etc., is not standard Markdown for headings. These should be proper headings (e.g., ### TiDB) to maintain correct document structure and hierarchy.1
Style Guide References
| + TiDB | |
| ### TiDB |
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| * Memory control for the statistics cache is generally available (GA) [#45367](https://github.com/pingcap/tidb/issues/45367) @[hawkingrei](https://github.com/hawkingrei) | ||
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| TiDB instances can cache table statistics to accelerate execution plan generation and improve SQL performance. Starting from v6.1.0, TiDB introduces the system variable [`tidb_stats_cache_mem_quota`](https://github.com/system-variables.md#tidb_stats_cache_mem_quota-new-in-v610). By configuring this system variable, you can set a memory usage limit for the statistics cache. When the cache reaches its limit, TiDB automatically evicts inactive cache entries, helping control instance memory usage and improve stability. |
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The link https://github.com/system-variables.md#tidb_stats_cache_mem_quota-new-in-v610 appears to be incorrect as it points to GitHub directly for a documentation page. It should likely be a relative link within the docs, such as /system-variables.md#tidb_stats_cache_mem_quota-new-in-v610.1
Style Guide References
| TiDB instances can cache table statistics to accelerate execution plan generation and improve SQL performance. Starting from v6.1.0, TiDB introduces the system variable [`tidb_stats_cache_mem_quota`](https://github.com/system-variables.md#tidb_stats_cache_mem_quota-new-in-v610). By configuring this system variable, you can set a memory usage limit for the statistics cache. When the cache reaches its limit, TiDB automatically evicts inactive cache entries, helping control instance memory usage and improve stability. | |
| TiDB instances can cache table statistics to accelerate execution plan generation and improve SQL performance. Starting from v6.1.0, TiDB introduces the system variable [`tidb_stats_cache_mem_quota`](/system-variables.md#tidb_stats_cache_mem_quota-new-in-v610). By configuring this system variable, you can set a memory usage limit for the statistics cache. When the cache reaches its limit, TiDB automatically evicts inactive cache entries, helping control instance memory usage and improve stability. |
Footnotes
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| * TiDB supports partition type management [#42728](https://github.com/pingcap/tidb/issues/42728) @[mjonss](https://github.com/mjonss) | ||
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| Before v7.4.0, partition types of partitioned tables in TiDB cannot be modified. Starting from v7.4.0, TiDB supports modifying partitioned tables to non-partitioned tables or non-partitioned tables to partitioned tables, and supports changing partition types. Hence, now you can flexibly adjust the partition type and number for a partitioned table. For example, you can use the `ALTER TABLE t PARTITION BY ...` statement to modify the partition type. |
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Consider rephrasing "Hence, now you can" to "Hence, you can now" for better flow.1
Style Guide References
| Before v7.4.0, partition types of partitioned tables in TiDB cannot be modified. Starting from v7.4.0, TiDB supports modifying partitioned tables to non-partitioned tables or non-partitioned tables to partitioned tables, and supports changing partition types. Hence, now you can flexibly adjust the partition type and number for a partitioned table. For example, you can use the `ALTER TABLE t PARTITION BY ...` statement to modify the partition type. | |
| Before v7.4.0, partition types of partitioned tables in TiDB cannot be modified. Starting from v7.4.0, TiDB supports modifying partitioned tables to non-partitioned tables or non-partitioned tables to partitioned tables, and supports changing partition types. Hence, you can now flexibly adjust the partition type and number for a partitioned table. For example, you can use the `ALTER TABLE t PARTITION BY ...` statement to modify the partition type. |
Footnotes
| | TiFlash | [`profiles.default.enable_resource_control`](/tiflash/tiflash-configuration.md) | Newly added | Controls whether to enable the TiFlash resource control feature. | | ||
| | TiFlash | [`storage.format_version`](/tiflash/tiflash-configuration.md) | Modified | Change the default value from `4` to `5`. The new format can reduce the number of physical files by merging smaller files. | | ||
| | TiFlash | [`task_scheduler_active_set_soft_limit`](/tiflash/tiflash-configuration.md#task_scheduler_active_set_soft_limit-new-in-v640) | Modified | Change the default value from `vcpu * 0.25` to `vcpu * 2`. | | ||
| | Dumpling | [`--csv-line-terminator`](/dumpling-overview.md#option-list-of-dumpling) | Newly added | Specifies the desired terminator of CSV files . This option supports `"\r\n"` and `"\n"`. The default value is `"\r\n"`, which is consistent with the earlier versions. | |
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There is an extra space before the period at the end of "CSV files .".1
Style Guide References
| | Dumpling | [`--csv-line-terminator`](/dumpling-overview.md#option-list-of-dumpling) | Newly added | Specifies the desired terminator of CSV files . This option supports `"\r\n"` and `"\n"`. The default value is `"\r\n"`, which is consistent with the earlier versions. | | |
| | Dumpling | [`--csv-line-terminator`](/dumpling-overview.md#option-list-of-dumpling) | Newly added | Specifies the desired terminator of CSV files. This option supports `"\r\n"` and `"\n"`. The default value is `"\r\n"`, which is consistent with the earlier versions. | |
Footnotes
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| ## Deprecated and removed features | ||
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| + [Mydumper](https://docs-archive.pingcap.com/tidb/v4.0/mydumper-overview) will be deprecated in v7.5.0 and most of its features have been replaced by [Dumpling](/dumpling-overview.md). It is strongly recommended that you use Dumpling instead of mydumper. |
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The capitalization of "Mydumper" is inconsistent. The link text is "Mydumper", while the subsequent mention is "mydumper". Please ensure consistent capitalization.1
Style Guide References
| + [Mydumper](https://docs-archive.pingcap.com/tidb/v4.0/mydumper-overview) will be deprecated in v7.5.0 and most of its features have been replaced by [Dumpling](/dumpling-overview.md). It is strongly recommended that you use Dumpling instead of mydumper. | |
| + [Mydumper](https://docs-archive.pingcap.com/tidb/v4.0/mydumper-overview) will be deprecated in v7.5.0 and most of its features have been replaced by [Dumpling](/dumpling-overview.md). It is strongly recommended that you use Dumpling instead of Mydumper. |
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| ### Scalability | ||
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| * Support selecting the TiDB nodes to parallelly execute the backend `ADD INDEX` or `IMPORT INTO` tasks of the Distributed eXecution Framework (DXF) (experimental) [#46453](https://github.com/pingcap/tidb/pull/46453) @[ywqzzy](https://github.com/ywqzzy) |
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The word "parallelly" is a bit uncommon. Consider using "in parallel" for better readability.1
Style Guide References
| * Support selecting the TiDB nodes to parallelly execute the backend `ADD INDEX` or `IMPORT INTO` tasks of the Distributed eXecution Framework (DXF) (experimental) [#46453](https://github.com/pingcap/tidb/pull/46453) @[ywqzzy](https://github.com/ywqzzy) | |
| * Support selecting the TiDB nodes to execute the backend `ADD INDEX` or `IMPORT INTO` tasks of the Distributed eXecution Framework (DXF) in parallel (experimental) [#46453](https://github.com/pingcap/tidb/pull/46453) @[ywqzzy](https://github.com/ywqzzy) |
Footnotes
| </tr> | ||
| <tr> | ||
| <td>DB Operations and Observability</td> | ||
| <td>Specify<a href="https://docs-archive.pingcap.com/tidb/v7.4/system-variables#tidb_service_scope-new-in-v740" target="_blank"> the respective TiDB nodes</a> to execute the <code>IMPORT INTO</code> and <code>ADD INDEX</code> SQL statements (experimental)</td> |
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A space is missing between "Specify" and the link markup <a>. Adding a space improves readability.1
Style Guide References
| <td>Specify<a href="https://docs-archive.pingcap.com/tidb/v7.4/system-variables#tidb_service_scope-new-in-v740" target="_blank"> the respective TiDB nodes</a> to execute the <code>IMPORT INTO</code> and <code>ADD INDEX</code> SQL statements (experimental)</td> | |
| <td>Specify <a href="https://docs-archive.pingcap.com/tidb/v7.4/system-variables#tidb_service_scope-new-in-v740" target="_blank"> the respective TiDB nodes</a> to execute the <code>IMPORT INTO</code> and <code>ADD INDEX</code> SQL statements (experimental)</td> |
Footnotes
| ##### `task_scheduler_active_set_soft_limit` <span class="version-mark">New in v6.4.0</span> | ||
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| - This item is used for the MinTSO scheduler. It specifies the maximum number of queries that can run simultaneously in a TiFlash instance. For more information, see [TiFlash MinTSO Scheduler](/tiflash/tiflash-mintso-scheduler.md). | ||
| - Default value: Before v7.4.0, the default value is `vcpu * 0.25`, which means a quarter of the number of vCPUs. Starting from v7.4.0, the default value is `vcpu * 2`, which means twice the number of vCPUs. |
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The description of the default value change for task_scheduler_active_set_soft_limit is clear and accurately reflects the change mentioned in the PR title. Ensure that vcpu is consistently understood as virtual CPU count in this context.1
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Footnotes
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This is an automated cherry-pick of #21137
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By default, CHOOSE MASTER ONLY so your changes will be applied to the next TiDB major or minor releases. If your PR involves a product feature behavior change or a compatibility change, CHOOSE THE AFFECTED RELEASE BRANCH(ES) AND MASTER.
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What is the related PR or file link(s)?
task_scheduler_active_set_soft_limitdocs-cn#20474Do your changes match any of the following descriptions?