VTTablet: Transmit raw MySQL packets for Fields and Rows over wire with grpc buffer

[harshit-gangal]

Description

In this PR, VTTablet sends raw MySQL packets to VTGate avoiding two conversion

1. MySQL to sqltypes.Result
2. sqltypes.Result to Proto

In this approach, the raw packets received from the MySQL is prefixed with the proto header and using mem.BufferSlice are send as-is over GRPC transport layer avoiding the double cost of conversions.

VTGate on the receiving side will convert the raw packets to sqltypes.Result, earlier the conversion was from proto to sqltypes.Result.

Related Issue(s)

• [wip] Raw MySQL packets #15522
• Closes Use Raw MySQL packets when passing results back from VTTablet to VTGate #17080
• Resolves VTTablet allocation reduction #17172

Checklist

• Tests were added or are not required
• Did the new or modified tests pass consistently locally and on CI?
• Documentation was added or is not required

[vitess-bot]

Review Checklist

Hello reviewers! 👋 Please follow this checklist when reviewing this Pull Request.

General

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Tests

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Backward compatibility

• Protobuf changes should be wire-compatible.
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• vtctl command output order should be stable and awk-able.

[vitess-bot]

Hello! 👋

This Pull Request is now handled by arewefastyet. The current HEAD and future commits will be benchmarked.

You can find the performance comparison on the arewefastyet website.

[codecov]

Codecov Report

Attention: Patch coverage is 39.29471% with 241 lines in your changes missing coverage. Please review.

Project coverage is 67.34%. Comparing base (216fd70) to head (98f53c1).

Files with missing lines	Patch %	Lines
go/mysql/query.go	23.64%	113 Missing ⚠️
go/mysql/conn.go	12.50%	77 Missing ⚠️
go/mysql/result.go	60.27%	29 Missing ⚠️
go/vt/vttablet/grpctabletconn/conn.go	41.17%	10 Missing ⚠️
go/vt/servenv/grpc_codec.go	78.26%	5 Missing ⚠️
go/vt/vttablet/grpcqueryservice/server.go	16.66%	5 Missing ⚠️
go/vt/vttablet/tabletserver/query_executor.go	90.00%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #17135      +/-   ##
==========================================
- Coverage   67.39%   67.34%   -0.06%     
==========================================
  Files        1570     1571       +1     
  Lines      252917   253250     +333     
==========================================
+ Hits       170446   170541      +95     
- Misses      82471    82709     +238     

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