update async commit related documentations by sticnarf · Pull Request #5607 · pingcap/docs-cn

sticnarf · 2021-02-25T05:42:25Z

What is changed, added or deleted? (Required)

TiDB 5.0 GA will not contain configurations related to async commit or 1PC. So they are removed.

And we also introduce a weaker consistency model for transactions. Add documentations about it.

Which TiDB version(s) do your changes apply to? (Required)

Do your changes match any of the following descriptions?

Delete files
Change aliases
Need modification after applied to another branch
Might cause conflicts after applied to another branch

TomShawn · 2021-02-25T07:01:39Z

@sticnarf Please involve a technical review.

sticnarf · 2021-02-25T07:10:49Z

@youjiali1995 Could you help review the doc, especially the part of starting transactions with causal consistency?

Signed-off-by: Yilin Chen <sticnarf@gmail.com>

youjiali1995

rest LGTM

youjiali1995 · 2021-02-25T07:25:13Z

 + TiKV 的负载阈值，如果超过此阈值，会收集更多的 batch 封包，来减轻 TiKV 的压力。仅在 `tikv-client.max-batch-size` 值大于 0 时有效，不推荐修改该值。
 + 默认值：200

-## tikv-client.async-commit <span class="version-mark">从 v5.0.0-rc 版本开始引入</span>


Why remove them?

The PM does not want to expose these advanced parameters to the user. pingcap/tidb#22945 removes these parameters from the example.

youjiali1995 · 2021-02-25T07:35:19Z


-![BeginTransactionStmt](/media/sqlgram/BeginTransactionStmt.png)
+```ebnf+diagram
+BeginTransactionStmt


Seems the format isn't unified. All other places are

BeginTransactionStmt := 'BEGIN' ( 'PESSIMISTIC' | 'OPTIMISTIC' )? | 'START' 'TRANSACTION' ...

The EBNF in other places does not have multiple indentations. Now I put the second closure in one line like others...

youjiali1995 · 2021-02-25T08:02:26Z

+           ( 'READ' ( 'WRITE' | 'ONLY' ( 'WITH' 'TIMESTAMP' 'BOUND' TimestampBound )? )
+           | 'WITH' 'CONSISTENT' 'SNAPSHOT'
+           | 'WITH' 'CAUSAL' 'CONSISTENCY' 'ONLY' )?


I prefer to add indents here.

Signed-off-by: Yilin Chen <sticnarf@gmail.com>

youjiali1995

/LGTM

ti-srebot · 2021-02-25T09:16:48Z

@youjiali1995, Thanks for your review. The bot only counts LGTMs from Reviewers and higher roles, but you're still welcome to leave your comments. See the corresponding SIG page for more information. Related SIG: docs(slack).

ti-srebot · 2021-02-27T09:17:10Z

@TomShawn, @youjiali1995, PTAL.

Co-authored-by: Grace Cai <qqzczy@126.com> Co-authored-by: TomShawn <41534398+TomShawn@users.noreply.github.com>

Signed-off-by: Yilin Chen <sticnarf@gmail.com>

qiancai · 2021-03-23T09:28:19Z


 - 作用域：SESSION | GLOBAL
- 默认值：对于新创建的集群，v5.0.0-rc 版本默认值为 OFF，自 v5.0.0 GA 版本起默认值为 ON。对于升级到 v5.0.0 GA 版本的集群，如果升级前是 v5.0.0-rc 版本，升级不改变该变量的值；如果升级前是 v4.0 及之前版本，升级后默认值为 OFF。
+- 默认值：对于新创建的集群，v5.0 RC 版本默认值为 OFF，自 v5.0 GA 版本起默认值为 ON。对于升级到 v5.0 GA 版本的集群，如果升级前是 v5.0 RC 版本，升级不改变该变量的值；如果升级前是 v4.0 及之前版本，升级后默认值为 OFF。


Suggested change

- 默认值：对于新创建的集群，v5.0 RC 版本默认值为 OFF，自 v5.0 GA 版本起默认值为 ON。对于升级到 v5.0 GA 版本的集群，如果升级前是 v5.0 RC 版本，升级不改变该变量的值；如果升级前是 v4.0 及之前版本，升级后默认值为 OFF。

- 默认值：对于新创建的集群，默认值为 ON。对于升级版本的集群，如果升级前是 v5.0 RC 及之后版本，升级不改变该变量的值；如果升级前是 v4.0 及之前版本，升级后默认值为 OFF。

Signed-off-by: Yilin Chen <sticnarf@gmail.com>

qiancai · 2021-03-23T09:38:02Z


+> **注意：**
+>
+> 启用 TiDB Binlog 后，开启该选项无法获得性能提升。如果可能，建议使用 [TiCDC](/ticdc/ticdc-overview.md) 替代。


Suggested change

> 启用 TiDB Binlog 后，开启该选项无法获得性能提升。如果可能，建议使用 [TiCDC](/ticdc/ticdc-overview.md) 替代。

> 启用 TiDB Binlog 后，开启该选项无法获得性能提升。要获得性能提升，建议使用 [TiCDC](/ticdc/ticdc-overview.md) 替代 TiDB Binlog。

Signed-off-by: Yilin Chen <sticnarf@gmail.com>

TomShawn · 2021-03-23T09:48:27Z

 ### `tidb_enable_async_commit` <span class="version-mark">从 v5.0.0-rc 版本开始引入</span>

-> **警告：**
->
-> 当前该功能为实验特性，不建议在生产环境中使用。目前存在已知问题有：
+- 作用域：SESSION | GLOBAL
+- 默认值：对于新创建的集群，默认值为 ON。对于升级版本的集群，如果升级前是 v5.0 RC 及之后版本，升级不改变该变量的值；如果升级前是 v4.0 及之前版本，升级后默认值为 OFF。
+- 该变量控制是否启用 Async Commit 特性，使事务两阶段提交的第二阶段于后台异步进行。开启本特性能降低事务提交的延迟。
+
+> **注意：**
 >
-> + 暂时与 [TiCDC](/ticdc/ticdc-overview.md) 不兼容，可能导致 TiCDC 运行不正常。
-> + 暂时与 [Compaction Filter](/tikv-configuration-file.md#enable-compaction-filter-从-v500-rc-版本开始引入) 不兼容，共同使用时有小概率发生写丢失。
-> + 本特性与 TiDB Binlog 不兼容，开启 TiDB Binlog 时本配置将不生效。
+> 启用 TiDB Binlog 后，开启该选项无法获得性能提升。要获得性能提升，建议使用 [TiCDC](/ticdc/ticdc-overview.md) 替代 TiDB Binlog。
+
+### `enable-one-pc` <span class="version-mark">从 v5.0.0-rc 版本开始引入</span>

 - 作用域：SESSION | GLOBAL
- 默认值：OFF
- 该变量控制是否启用 Async Commit 特性，使事务两阶段提交的第二阶段于后台异步进行。开启本特性能降低事务提交的延迟。
+- 默认值：对于新创建的集群，默认值为 ON。对于升级版本的集群，如果升级前是 v5.0 RC 及之后版本，升级不改变该变量的值；如果升级前是 v4.0 及之前版本，升级后默认值为 OFF。
+- 指定是否在只涉及一个 Region 的事务上启用一阶段提交特性。比起传统两阶段提交，一阶段提交能大幅降低事务提交延迟并提升吞吐。

-> **警告：**
+> **注意：**
 >
-> 开启本特性时，默认不保证事务的外部一致性。具体请参考 [`tidb_guarantee_external_consistency`](#tidb_guarantee_external_consistency-从-v500-rc-版本开始引入) 系统变量。
+> 启用 TiDB Binlog 后，开启该选项无法获得性能提升。要获得性能提升，建议使用 [TiCDC](/ticdc/ticdc-overview.md) 替代 TiDB Binlog。


这一部分的变量有涉及因果一致性的内容吗？是否需要在这里提到因果一致性，或是在因果一致性的内容里提到 async commit? 二者是否有关系呢？

Signed-off-by: Yilin Chen <sticnarf@gmail.com>

Co-authored-by: TomShawn <41534398+TomShawn@users.noreply.github.com>

TomShawn · 2021-03-24T03:38:06Z

/lgtm

TomShawn · 2021-03-24T03:40:11Z

/remove-status require-change
/label require-LGT1

TomShawn · 2021-03-24T03:40:24Z

/merge

ti-chi-bot · 2021-03-24T03:40:26Z

This pull request has been accepted and is ready to merge.

Details

Commit hash: c0cc15b

Signed-off-by: ti-srebot <ti-srebot@pingcap.com>

ti-srebot · 2021-03-24T03:42:11Z

cherry pick to release-5.0 in PR #5812

TomShawn · 2021-03-24T03:54:00Z

release-5.0: 【对于新创建的集群，5.0 RC 默认值为 OFF】

TomShawn · 2021-03-25T08:28:26Z

/remove-translation doing
/translation done

sticnarf force-pushed the async-commit-5.0-ga branch 6 times, most recently from 6e460f4 to 2ca4f59 Compare February 25, 2021 06:14

TomShawn reviewed Feb 25, 2021

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Comment thread sql-statements/sql-statement-start-transaction.md

TomShawn self-assigned this Feb 25, 2021

TomShawn added needs-cherry-pick-5.0 size/medium Changes of a medium size. status/PTAL This PR is ready for reviewing. translation/doing This PR’s assignee is translating this PR. labels Feb 25, 2021

sticnarf force-pushed the async-commit-5.0-ga branch 2 times, most recently from 548e38c to 89cbb3c Compare February 25, 2021 07:09

update async commit related documentations

2c91e50

Signed-off-by: Yilin Chen <sticnarf@gmail.com>

sticnarf force-pushed the async-commit-5.0-ga branch from 89cbb3c to 2c91e50 Compare February 25, 2021 07:12

TomShawn requested a review from youjiali1995 February 25, 2021 07:17

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sticnarf mentioned this pull request Feb 25, 2021

config: remove async commit configs from example pingcap/tidb#22945

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reformat EBNF

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Signed-off-by: Yilin Chen <sticnarf@gmail.com>

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Merge branch 'master' into async-commit-5.0-ga

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sticnarf and others added 2 commits March 23, 2021 17:13

Apply suggestions from code review

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Co-authored-by: Grace Cai <qqzczy@126.com> Co-authored-by: TomShawn <41534398+TomShawn@users.noreply.github.com>

update binlog related doc

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Signed-off-by: Yilin Chen <sticnarf@gmail.com>

qiancai reviewed Mar 23, 2021

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remove version-specific description

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improve wording

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sticnarf added 2 commits March 23, 2021 18:02

some fixes

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fix broken link

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Update transaction-overview.md

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ti-chi-bot merged commit 97b43be into pingcap:master Mar 24, 2021

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cherry pick pingcap#5607 to release-5.0

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update async commit related documentations (#5607) #5812

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update async commit related documentations (#5607) (#5812)

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update async commit related documentation pingcap/docs#5114

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update async commit related documentation (#5114) pingcap/docs#5131

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	- 默认值：对于新创建的集群，v5.0 RC 版本默认值为 OFF，自 v5.0 GA 版本起默认值为 ON。对于升级到 v5.0 GA 版本的集群，如果升级前是 v5.0 RC 版本，升级不改变该变量的值；如果升级前是 v4.0 及之前版本，升级后默认值为 OFF。
	- 默认值：对于新创建的集群，默认值为 ON。对于升级版本的集群，如果升级前是 v5.0 RC 及之后版本，升级不改变该变量的值；如果升级前是 v4.0 及之前版本，升级后默认值为 OFF。

	> 启用 TiDB Binlog 后，开启该选项无法获得性能提升。如果可能，建议使用 [TiCDC](/ticdc/ticdc-overview.md) 替代。
	> 启用 TiDB Binlog 后，开启该选项无法获得性能提升。要获得性能提升，建议使用 [TiCDC](/ticdc/ticdc-overview.md) 替代 TiDB Binlog。

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sticnarf commented Feb 25, 2021

What is changed, added or deleted? (Required)

Which TiDB version(s) do your changes apply to? (Required)

Do your changes match any of the following descriptions?

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