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*: Provide staleReadProcessor to process stale read #32699

Merged
merged 21 commits into from
Mar 8, 2022
Merged

*: Provide staleReadProcessor to process stale read #32699

merged 21 commits into from
Mar 8, 2022

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lcwangchao
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What problem does this PR solve?

Issue Number: close #32697

What is changed and how it works?

This is one of the PRs to refactor stale read. The full draft is here: #32325

This modifications of the PR includes:

  • Introduce a new package staleread to provide stale read related functions.
  • Introduce a new interface staleread.Processor to provide methods processing and fetching stale read context.
  • Move some of the stale read processing codes to staleread.staleReadProcessor which implements staleread.Processor to simplify Preprocessor .

For the PRs in the future, we'll do more things refactoring stale read, including:

  • Move more stale read codes (prepare/execute/begin) to processor.
  • Separate the processor the some sub classes for different scenes (Prepare, CreateView, InitTxnContext ...).
  • Provide StaleReadTxnContextProvider and set it to TxnManager in processor

Check List

Tests

  • Unit test
  • Integration test
  • Manual test (add detailed scripts or steps below)
  • No code

Side effects

  • Performance regression: Consumes more CPU
  • Performance regression: Consumes more Memory
  • Breaking backward compatibility

Documentation

  • Affects user behaviors
  • Contains syntax changes
  • Contains variable changes
  • Contains experimental features
  • Changes MySQL compatibility

Release note

None

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ti-chi-bot commented Mar 1, 2022 •
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[REVIEW NOTIFICATION]

This pull request has been approved by:

  • Yisaer
  • xhebox

To complete the pull request process, please ask the reviewers in the list to review by filling /cc @reviewer in the comment.
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 release-note-none Denotes a PR that doesn't merit a release note. size/XL Denotes a PR that changes 500-999 lines, ignoring generated files. labels Mar 1, 2022
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/run-unit-test
/run-mysql-test

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sre-bot commented Mar 1, 2022 •
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Code Coverage Details: https://codecov.io/github/pingcap/tidb/commit/c350f1eee8aee91a0c86c1e549f574e96073138d

@lcwangchao
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/run-mysql-test

@ti-chi-bot ti-chi-bot added size/XXL Denotes a PR that changes 1000+ lines, ignoring generated files. and removed size/XL Denotes a PR that changes 500-999 lines, ignoring generated files. labels Mar 2, 2022
@lcwangchao
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/run-mysql-test

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/run-unit-test

@lcwangchao lcwangchao requested review from Yisaer, xhebox and JmPotato March 2, 2022 08:09
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/run-unit-test
/run-mysql-test

JmPotato
JmPotato reviewed Mar 3, 2022
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planner/core/preprocess.go
@@ -184,6 +188,8 @@ type preprocessor struct {
tableAliasInJoin []map[string]interface{}
withName map[string]interface{}

staleReadProcessor staleread.Processor
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Though I'm OK to make this change, does this mean that we may have more and more xxxProcessor fields in the future? Do we have any idea on how to simplify this part?

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Having a staleReadProcessor here is to decouple the stale read code from preprocessor and expect to reuse it. It is only a choice for stale read and I think for other scenes the design will not be limited to 'xxxProcessor'.

For stale read, in the future, there is still only one processor to process stale read. However, we can have multiple subclasses inherits staleread.Processor and we can use one of them according to the exact scenario

planner/core/preprocess.go Show resolved Hide resolved
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/run-unit-test

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/run-unit-test
/run-mysql-test

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/run-unit-test

xhebox
xhebox reviewed Mar 4, 2022
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LGTM overall

sessiontxn/staleread/processor.go Show resolved Hide resolved
@ti-chi-bot ti-chi-bot added the status/LGT1 Indicates that a PR has LGTM 1. label Mar 4, 2022
Yisaer
Yisaer reviewed Mar 7, 2022
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rest lgtm

sessiontxn/staleread/processor.go
Comment on lines +139 to +140
// OnSelectTable will be called when process table in select statement
func (p *staleReadProcessor) OnSelectTable(tn *ast.TableName) error {
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Why the comment for explaining the code logic removed?

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I'll complete it later

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done

sessiontxn/staleread/main_test.go Outdated Show resolved Hide resolved
@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 Mar 8, 2022
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/merge

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

Commit hash: 371a42b

@ti-chi-bot ti-chi-bot added the status/can-merge Indicates a PR has been approved by a committer. label Mar 8, 2022
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/run-mysql-test

@ti-chi-bot ti-chi-bot removed the status/can-merge Indicates a PR has been approved by a committer. label Mar 8, 2022
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/run-mysql-test

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/merge

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

Commit hash: c350f1e

@ti-chi-bot ti-chi-bot added the status/can-merge Indicates a PR has been approved by a committer. label Mar 8, 2022
@ti-chi-bot ti-chi-bot merged commit f79d2a5 into pingcap:master Mar 8, 2022
@lcwangchao lcwangchao mentioned this pull request Apr 19, 2022
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@lcwangchao lcwangchao deleted the stalereadprocessor branch July 5, 2022 03:42
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@JmPotato JmPotato JmPotato left review comments

@Yisaer Yisaer Yisaer approved these changes

@xhebox xhebox xhebox approved these changes

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Provide staleReadProcessor to process stale read
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@lcwangchao @ti-chi-bot @sre-bot @JmPotato @xhebox @Yisaer