executor: some minor refine for hash join v2 build

[windtalker]

What problem does this PR solve?

Issue Number: ref #53127

Problem Summary:

What changed and how does it work?

1. During hash join v2 build, it will pre-allocate maxRowTableSegmentSize(which is 1024) rows for a new rowTableSegment
   

   tidb/pkg/executor/join/join_row_table.go

   Lines 87 to 95 in 634ac69

   	func newRowTableSegment() *rowTableSegment {
   	return &rowTableSegment{
   	// TODO: @XuHuaiyu if joinKeyIsInlined, the cap of rawData can be calculated
   	rawData: make([]byte, 0),
   	hashValues: make([]uint64, 0, maxRowTableSegmentSize),
   	rowStartOffset: make([]uint64, 0, maxRowTableSegmentSize),
   	validJoinKeyPos: make([]int, 0, maxRowTableSegmentSize),
   	}
   	}

   
   For small queries, it is a waste to pre allocate so many memories and may hurt the performance in high concurrency scenarios.
   In this pr, when constructing a new rowTableSegment, it will use chunk_row_number/partition_number * 1.2 as the row size hint for the first rowTableSegment, but still use maxRowTableSegmentSize as the row size hint for the following rowTableSegment.

2. Add maxRowTableSegmentByteSize to control the max memory size of a rowTableSegment.

3. Since rowTableSegment saves rowStartOffset directly, there is no need to save row offset in builder.startPosInRawData, so remove startPosInRawData in rowTableBuilder

4. rename crrntSizeOfRowTable to rowNumberInCurrentRowTableSeg

Check List

Tests

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

  • I checked and no code files have been changed.

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

Please refer to Release Notes Language Style Guide to write a quality release note.

None

[tiprow]

Hi @windtalker. Thanks for your PR.

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[xzhangxian1008]

/assign

[codecov]

Codecov Report

Attention: Patch coverage is 0% with 28 lines in your changes missing coverage. Please review.

Project coverage is 55.0895%. Comparing base (a48a4a2) to head (2ef007d).

Additional details and impacted files

@@                Coverage Diff                @@
##             master     #54429         +/-   ##
=================================================
- Coverage   72.6973%   55.0895%   -17.6078%     
=================================================
  Files          1551       1672        +121     
  Lines        437184     609272     +172088     
=================================================
+ Hits         317821     335645      +17824     
- Misses        99756     250669     +150913     
- Partials      19607      22958       +3351     

Flag	Coverage Δ
integration	19.9170% <0.0000%> (?)

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Components	Coverage Δ
dumpling	52.9656% <ø> (ø)
parser	∅ <ø> (∅)
br	52.4834% <ø> (+6.6429%)	⬆️

[xzhangxian1008]

LGTM

[ti-chi-bot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: XuHuaiyu, xzhangxian1008

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[ti-chi-bot]

[LGTM Timeline notifier]

Timeline:

• 2024-07-05 03:03:10.663133375 +0000 UTC m=+1552717.148622205: ☑️ agreed by xzhangxian1008.
• 2024-07-08 06:37:39.268194276 +0000 UTC m=+253156.503428389: ☑️ agreed by XuHuaiyu.

[hawkingrei]

/retest