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Add docs for sysvar cache #6464

Merged
merged 3 commits into from
Jun 17, 2021
Merged

Add docs for sysvar cache #6464

merged 3 commits into from
Jun 17, 2021

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Liuxiaozhen12
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What is changed, added or deleted? (Required)

This is the docs for pingcap/tidb#24359 which has not merged yet. It more accurately reflects the future-state of sysvars.

There is another PR for GA releases which describes how it previously worked better: #5562

It needs a "followup" to insert the version the change is effective from.

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  • master (the latest development version)
  • v5.1 (TiDB 5.1 versions)
  • v5.0 (TiDB 5.0 versions)
  • v4.0 (TiDB 4.0 versions)
  • v3.1 (TiDB 3.1 versions)
  • v3.0 (TiDB 3.0 versions)
  • v2.1 (TiDB 2.1 versions)

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Do your changes match any of the following descriptions?

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

@ti-chi-bot ti-chi-bot requested a review from TomShawn June 17, 2021 03:36
@ti-chi-bot ti-chi-bot added missing-translation-status This PR does not have translation status info. size/XS Denotes a PR that changes 0-9 lines, ignoring generated files. labels Jun 17, 2021
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/label requires-followup
/label v5.1
/translation from-docs
/label requires-version-specific-changes

@ti-chi-bot ti-chi-bot added translation/from-docs This PR is translated from a PR in pingcap/docs. requires-followup This PR requires a follow-up task after being merged. v5.1 This PR/issue applies to TiDB v5.1. requires-version-specific-changes After cherry-picked, the cherry-picked PR requires further changes. and removed missing-translation-status This PR does not have translation status info. labels Jun 17, 2021
@Liuxiaozhen12 Liuxiaozhen12 mentioned this pull request Jun 17, 2021
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@Liuxiaozhen12 Liuxiaozhen12 requested a review from morgo June 17, 2021 05:12
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morgo commented Jun 17, 2021

/cc @xhebox

I can't read it :-)

@ti-chi-bot ti-chi-bot requested a review from xhebox June 17, 2021 05:14
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Rest LGTM

system-variables.md Outdated
@@ -25,8 +25,8 @@ SET GLOBAL tidb_distsql_scan_concurrency = 10;

> **注意：**
>
> - 在 TiDB 中，`GLOBAL` 变量的设置即使重启后也仍然有效。每隔 2 秒，其他 TiDB server 会获取到对变量设置的更改。详情见 [TiDB #14531](https://github.com/pingcap/tidb/issues/14531)。
> - 此外，由于应用和连接器通常需要读 MySQL 变量，为了兼容这一需求，在 TiDB 中，部分 MySQL 5.7 的变量既可读取也可设置。例如，尽管 JDBC 连接器不依赖于查询缓存 (query cache) 的行为，但仍然可以读取和设置查询缓存。
> - 当语句发出后，`SET GLOBAL` 会在 TiDB 服务器上立即执行。之后，通知会发送到所有 TiDB 服务器上以刷新其系统变量缓存，该操作会在后台立即开始。由于某些 TiDB 服务器可能会错过通知，系统变量缓存每 30 秒会自动刷新一次。这有助于确保所有服务器都以相同的配置运行。
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当语句发出后，SET GLOBAL 会在 TiDB 服务器上立即执行。之后，通知会发送到所有 TiDB 服务器上以刷新其系统变量缓存

意思对了, 但是不太自然, 也许类似

SET GLOBAL 语句在执行它的 TiDB 服务器上会立刻起效. 之后会通知所有TiDB 服务器...

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请问第一句改成这样可以如何？Thx！

在 TiDB 服务器上执行 SET GLOBAL 语句后，该更改会立即生效。之后会通知所有 TiDB 服务器刷新其系统变量缓存……

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LGTM

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@xhebox: Thanks for your review. The bot only counts approvals from reviewers and higher roles in list, but you're still welcome to leave your comments.

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LGTM

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@Liuxiaozhen12 Liuxiaozhen12 removed the request for review from morgo June 17, 2021 07:43
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LGTM

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[REVIEW NOTIFICATION]

This pull request has been approved by:

  • TomShawn

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After your PR has acquired the required number of LGTMs, you can assign this pull request to the committer in the list by filling /assign @committer in the comment to help you merge this pull request.

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@ti-chi-bot ti-chi-bot added the status/LGT1 Indicates that a PR has LGTM 1. label Jun 17, 2021
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/remove-status LGT1
/status LGT2

@ti-chi-bot ti-chi-bot added status/LGT2 Indicates that a PR has LGTM 2. and removed status/LGT1 Indicates that a PR has LGTM 1. labels Jun 17, 2021
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/merge

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

Commit hash: e689949

@ti-chi-bot ti-chi-bot added the status/can-merge Indicates a PR has been approved by a committer. label Jun 17, 2021
@ti-chi-bot ti-chi-bot merged commit 3499735 into pingcap:master Jun 17, 2021
@Liuxiaozhen12 Liuxiaozhen12 deleted the Liuxiaozhen-patch-2 branch June 24, 2021 06:01
@TomShawn TomShawn added requires-followup This PR requires a follow-up task after being merged. and removed requires-followup This PR requires a follow-up task after being merged. labels Jul 2, 2021
3AceShowHand pushed a commit to 3AceShowHand/docs-cn that referenced this pull request Jul 27, 2021
@Liuxiaozhen12 @3AceShowHand
Add docs for sysvar cache (pingcap#6464)
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