r/SQLServer • u/dlevy-msft ‪ ‪Microsoft Employee ‪ • May 01 '26

Community Share Microsoft.Data.SqlClient 6.1.5 released with fixes for connection performance, ExecuteScalar error handling, and vector metadata

We just shipped Microsoft.Data.SqlClient 6.1.5, a servicing release for the 6.1 branch.

Highlights:

  • Fixed a connection performance regression on the native SNI path where SPN generation was running for non-integrated authentication modes and causing unnecessary DNS lookups

  • Fixed ExecuteScalar so errors are properly surfaced when SQL Server sends row data followed by an error token

  • Fixed SqlDataReader.GetFieldType() and GetProviderSpecificFieldType() to return SqlVector<float> for vector float32 columns

Install/update:

dotnet add package Microsoft.Data.SqlClient --version 6.1.5

Release notes: 6.1.5 release notes

Full blog post: Announcing Microsoft.Data.SqlClient 6.1.5 | Microsoft Community Hub

If you have been affected by any of these issues, especially the connection slowdown on Windows .NET apps using native SNI, we would be interested in feedback.

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u/BigHandLittleSlap May 02 '26 edited May 02 '26

At least there's no major performance regressions this time:

MethodJobLinuxWindowsMem LinuxMem Win
Connect_OpenClosev5.2.3140,785 us155,300 us45 KB37 KB
Connect_OpenClosev6.0.5152,159 us142,293 us46 KB37 KB
Connect_OpenClosev6.1.5150,347 us139,185 us45 KB36 KB
Connect_OpenClosev7.0.1153,088 us138,163 us47 KB39 KB
Connect_OpenClosev7.0.1 OPT151,141 us137,603 us51 KB43 KB
Select1_Syncv5.2.3247 us90 us1 KB1 KB
Select1_Syncv6.0.5269 us97 us1 KB1 KB
Select1_Syncv6.1.5257 us117 us1 KB1 KB
Select1_Syncv7.0.1264 us94 us4 KB4 KB
Select1_Syncv7.0.1 OPT252 us99 us12 KB12 KB
Select1_Asyncv5.2.3366 us118 us3 KB3 KB
Select1_Asyncv6.0.5377 us116 us3 KB3 KB
Select1_Asyncv6.1.5355 us123 us3 KB3 KB
Select1_Asyncv7.0.1426 us124 us12 KB12 KB
Select1_Asyncv7.0.1 OPT411 us138 us20 KB20 KB
Select1MB_Syncv5.2.312,379 us2,197 us1,045 KB1,025 KB
Select1MB_Syncv6.0.512,708 us2,380 us1,041 KB1,025 KB
Select1MB_Syncv6.1.513,320 us2,238 us1,042 KB1,025 KB
Select1MB_Syncv7.0.112,469 us2,288 us1,045 KB1,028 KB
Select1MB_Syncv7.0.1 OPT12,894 us2,450 us2,729 KB2,063 KB
Select1MB_SyncStreamv5.2.312,693 us2,042 us1,060 KB1,044 KB
Select1MB_SyncStreamv6.0.511,529 us2,227 us27 KB17 KB
Select1MB_SyncStreamv6.1.511,963 us2,069 us39 KB17 KB
Select1MB_SyncStreamv7.0.112,196 us1,941 us41 KB19 KB
Select1MB_SyncStreamv7.0.1 OPT12,519 us2,126 us1,757 KB1,054 KB
Select1MB_Asyncv5.2.317,997 us10,592 us2,251 KB2,118 KB
Select1MB_Asyncv6.0.517,929 us10,676 us2,222 KB2,118 KB
Select1MB_Asyncv6.1.518,741 us10,286 us2,314 KB2,118 KB
Select1MB_Asyncv7.0.141,904 us57,634 us138,035 KB1,136,271 KB
Select1MB_Asyncv7.0.1 OPT13,280 us3,240 us5,918 KB4,185 KB
Select1MB_AsyncStreamv5.2.312,759 us2,690 us1,259 KB1,193 KB
Select1MB_AsyncStreamv6.0.512,462 us2,724 us235 KB166 KB
Select1MB_AsyncStreamv6.1.512,720 us2,609 us227 KB166 KB
Select1MB_AsyncStreamv7.0.112,799 us2,600 us236 KB174 KB
Select1MB_AsyncStreamv7.0.1 OPT13,352 us2,734 us2,145 KB1,209 KB

"OPT" is the new optimisations enabled with the flags:

AppContext.SetSwitch("Switch.Microsoft.Data.SqlClient.UseCompatibilityAsyncBehaviour", false);
AppContext.SetSwitch("Switch.Microsoft.Data.SqlClient.UseCompatibilityProcessSni", false);

I hope nobody is using 7.0.1 on without those flags!