Improve async string perf and fix reading chars with initial offset. #3377

Wraith2 · 2025-05-26T20:26:25Z

Description

For performance related changes see background information in #3274 (comment) and the preceeding conversation. Reading a string in async mode was being slower than expected so I investigated. I will annotate each change with an explanation.

Issues

fixes #3331
fixes #3274

Testing

Tests have been added which cover both issues that are being fixed.

…decrease memcopy and gc time spent

…arameter

src/Microsoft.Data.SqlClient/netcore/src/Microsoft/Data/SqlClient/TdsParser.cs

Wraith2 · 2025-05-26T20:50:34Z

/cc @Tornhoof, @AlexanderKot this should fix your issues.

@dotnet/sqlclientdevteam can I get a CI kick? I'd really really like to get this in to preview 2 because it fixes all the known issues with async continue.

cheenamalhotra · 2025-05-27T00:05:21Z

/azp run

azure-pipelines · 2025-05-27T00:05:45Z

Azure Pipelines successfully started running 2 pipeline(s).

codecov · 2025-05-27T01:19:54Z

Codecov Report

Attention: Patch coverage is 0% with 12 lines in your changes missing coverage. Please review.

Project coverage is 59.71%. Comparing base (b8948f2) to head (e8df89e).
Report is 15 commits behind head on main.

Files with missing lines	Patch %	Lines
...nt/netfx/src/Microsoft/Data/SqlClient/TdsParser.cs	0.00%	6 Missing ⚠️
.../netcore/src/Microsoft/Data/SqlClient/TdsParser.cs	0.00%	5 Missing ⚠️
...c/Microsoft/Data/SqlClient/TdsParserStateObject.cs	0.00%	1 Missing ⚠️

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HEAD has 1 upload less than BASE

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addons 1 0

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3377      +/-   ##
==========================================
- Coverage   67.04%   59.71%   -7.33%     
==========================================
  Files         300      293       -7     
  Lines       65376    65308      -68     
==========================================
- Hits        43831    39000    -4831     
- Misses      21545    26308    +4763

Flag	Coverage Δ
addons	`?`
netcore	`63.02% <0.00%> (-9.17%)`	⬇️
netfx	`61.03% <0.00%> (-4.15%)`	⬇️

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Copilot

Pull Request Overview

This PR targets performance improvements in asynchronous string processing and corrects an issue with reading characters using an initial offset.

Added a new sequential character reading test ("CanGetCharsSequentially") to verify correct behavior.
Introduced helper methods in tests to use pooled buffers, ensuring buffers are resized appropriately.
Updated buffer management logic in TdsParser (both netfx and netcore) to use the correct offset and to improve buffer reallocation efficiency.

Reviewed Changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 3 comments.

File	Description
src/Microsoft.Data.SqlClient/tests/ManualTests/SQL/DataReaderTest/DataReaderTest.cs	Adds a new test and helper method for sequential character reading using pooled buffers.
src/Microsoft.Data.SqlClient/src/Microsoft/Data/SqlClient/TdsParserStateObject.cs	Introduces a GetPacketSize() method and a property to calculate the current packet index.
src/Microsoft.Data.SqlClient/netfx/src/Microsoft/Data/SqlClient/TdsParser.cs	Adjusts buffer sizing logic and offset handling to improve performance and correctness.
src/Microsoft.Data.SqlClient/netcore/src/Microsoft/Data/SqlClient/TdsParser.cs	Mirrors changes in netfx for improved buffer management and offset accumulation.

src/Microsoft.Data.SqlClient/tests/ManualTests/SQL/DataReaderTest/DataReaderTest.cs

src/Microsoft.Data.SqlClient/netfx/src/Microsoft/Data/SqlClient/TdsParser.cs

src/Microsoft.Data.SqlClient/netcore/src/Microsoft/Data/SqlClient/TdsParser.cs

src/Microsoft.Data.SqlClient/src/Microsoft/Data/SqlClient/TdsParserStateObject.cs

cheenamalhotra · 2025-05-28T05:28:53Z

/azp run

azure-pipelines · 2025-05-28T05:29:18Z

Azure Pipelines successfully started running 2 pipeline(s).

src/Microsoft.Data.SqlClient/netcore/src/Microsoft/Data/SqlClient/TdsParser.cs

benrr101

I can't say I know much about the internals here, so I appreciate the callouts on what changes are being made. However, I'm not understanding what the _longlen changes are really doing. Please take a look at my comments and I'll approve if you can explain it without code changes :)

src/Microsoft.Data.SqlClient/netcore/src/Microsoft/Data/SqlClient/TdsParser.cs

paulmedynski · 2025-06-02T12:44:25Z

/azp run

azure-pipelines · 2025-06-02T12:44:49Z

Azure Pipelines successfully started running 2 pipeline(s).

mdaigle · 2025-06-03T22:14:42Z

@benrr101 this one needs an updated review from you

benrr101

Thanks for making the changes!

…offset. (#3377)" This reverts commit 05df554.

* Revert 1af7327 * Revert "Fix TryReadPlpBytes throws ArgumentException (#3470) (#3474)" This reverts commit 0a55896. * Revert 44762d9 * Revert "Improve async string perf and fix reading chars with initial offset. (#3377)" This reverts commit 05df554. * Revert "Refine handling of moving between replay and continue states (#3337)" This reverts commit 265f522. * Revert "Fix SqlCached buffer async read with continue edge case. (#3329)" This reverts commit c3857b1. * Revert "Add `async` snapshot continue capability for multipacket fields (#3161)" This reverts commit 33364e7. * Revert "Add partial packet detection and fixup (#2714)" This reverts commit 8d5e4f2. * Remove methods previously moved to common file. * Supply byte buffer to vector read. * Minor compilation fixes that were missed in the reverts. * Remove partial packet context switch helpers. * Remove accidental duplication of SqlDataReader * Revert len change * Undo buff rental in netfx to simplify 6.0 diff. * Fix missed rented buff code. --------- Co-authored-by: Cheena Malhotra <[email protected]>

Wraith2 added 5 commits May 26, 2025 20:43

refine handling of moving between replay and continue states

412b873

for plp reads increase the buffer size in relatively small chunks to …

32d8b9e

…decrease memcopy and gc time spent

change TryReadPlpUnicodeChars to check plp length field not max len p…

e1964c9

…arameter

sync netfx and netcore

9638d61

add test covering dotnet#3331 and fix

8a8ffaa

Wraith2 requested a review from a team as a code owner May 26, 2025 20:26

Wraith2 commented May 26, 2025

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re-remove CurrentPacketIndex, fix test name error

68c4322

Wraith2 commented May 26, 2025

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Wraith2 commented May 26, 2025

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Wraith2 commented May 26, 2025

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cheenamalhotra added this to the 6.1-preview2 milestone May 27, 2025

cheenamalhotra requested a review from Copilot May 27, 2025 05:39

Copilot AI reviewed May 27, 2025

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cheenamalhotra reviewed May 27, 2025

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src/Microsoft.Data.SqlClient/src/Microsoft/Data/SqlClient/TdsParserStateObject.cs Outdated Show resolved Hide resolved

cheenamalhotra requested a review from a team May 27, 2025 17:23

paulmedynski previously approved these changes May 29, 2025

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mdaigle self-assigned this May 29, 2025

mdaigle requested changes May 29, 2025

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benrr101 requested changes May 29, 2025

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review feedback

e8df89e

Wraith2 dismissed paulmedynski’s stale review via e8df89e May 30, 2025 22:24

paulmedynski approved these changes Jun 2, 2025

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mdaigle approved these changes Jun 3, 2025

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benrr101 approved these changes Jun 4, 2025

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mdaigle merged commit 05df554 into dotnet:main Jun 4, 2025
237 checks passed

Wraith2 deleted the fix-3274 branch June 5, 2025 23:18

samsharma2700 added a commit that referenced this pull request Aug 5, 2025

Revert "Improve async string perf and fix reading chars with initial …

c39dc6f

…offset. (#3377)" This reverts commit 05df554.

mdaigle added a commit that referenced this pull request Aug 6, 2025

Revert "Improve async string perf and fix reading chars with initial …

2c83dc9

…offset. (#3377)" This reverts commit 05df554.

Improve async string perf and fix reading chars with initial offset. #3377

Improve async string perf and fix reading chars with initial offset. #3377

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Wraith2 commented May 26, 2025

Description

Issues

Testing

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Pull Request Overview

Reviewed Changes

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cheenamalhotra commented May 28, 2025

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Wraith2 commented May 26, 2025 •

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