PERF: Optimize pooled connection return while preserving transaction safety by sumitmsft · Pull Request #820 · microsoft/mssql-python

Sumit Sarabhai (sumitmsft) · 2026-09-25T16:30:21Z

AB#48076

Summary

This PR now replaces the earlier revert with a targeted pooling optimization. It retains the transaction, failure-discard, pool-capacity and native handle-lifetime protections from #777.

Skip pool sanitation only when a prior successful rollback/autocommit restoration established clean state and no subsequent statement allocation or uncertain operation invalidated it. A new login or deferred reset alone never establishes clean state.
Retained statement aliases, raw-handle exposure and unknown connection attributes remain conservative. Valid scalar login timeouts such as timeout=30 do not permanently disable the fast path.
Move close-time transaction handling into native code and consolidate required sanitation into one autocommit probe, metadata invalidation and GIL-release scope. Never turn autocommit on after a failed rollback.
Preserve cleanup gates, discard/capacity recovery, pool-generation and shutdown protections. Extend the existing explicit-transaction integration cases and add deterministic native failure/call-count coverage.

Scope and limitations

Used or uncertain connections still execute full transaction sanitation. This does not assume autocommit=True means there cannot be an explicit SQL transaction, and it does not remove safety synchronization to improve timings. End-to-end performance improvements and live SQL behavior remain subject to validation; no blanket regression-elimination claim is made.

Validation

Windows x64 Release extension and native test executable built successfully.
43 deterministic native sanitation cases passed; CTest passed.
24 targeted Python tests passed using the freshly built extension.
Positive-timeout coverage verifies that timeout 30 reaches physical login and that 100 subsequent unused pooled leases issue no sanitation calls.
Three expanded live-SQL integration cases collected successfully but were not executed locally. Normal cross-platform PR validation and performance evaluation are pending.

This reverts commit 2a86fc1 while preserving subsequent result-metadata changes. Restores the prior pooling behavior; the pooled-transaction correctness issue fixed by #777 will need a replacement fix. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

github-actions · 2026-09-25T16:30:38Z

PR Performance Report

✅ No regression detected

No consistent slowdowns detected across all 2 environments.

0 IMPROVEMENTS 0 SLOWDOWNS 2/2 ENVIRONMENTS

Coverage: 2 of 2 environments completed. Advisory result; does not block merging.

Performance diagnostics

Phase times are inclusive diagnostics and must not be added together. They identify where measured time changed, not why it changed.

Unix / SQL Server 2022

SELECT queries: ddbc::SQLBindColums +0.016 ms; ddbc::SQLExecDirect_wrap +0.003 ms; py::execute::cpp_call +0.002 ms. Call changes: ddbc::AppendDiagRecords::SQLGetDiagRec_call (added, removed, or intermittent).
Fetch-all queries: ddbc::SQLBindColums +0.004 ms; ddbc::FetchBatchData::cache_column_metadata +0.002 ms; ddbc::SQLNumResultCols_wrap +0.000 ms. Call changes: ddbc::AppendDiagRecords::SQLGetDiagRec_call (added, removed, or intermittent).
Row-by-row fetching: ddbc::SQLDescribeCol::driver_call +0.000 ms. Call changes: ddbc::AppendDiagRecords::SQLGetDiagRec_call (added, removed, or intermittent).
Batched row fetching: py::fetchmany::cpp_call +1.134 ms; ddbc::FetchMany_wrap +1.042 ms; ddbc::FetchBatchData +1.032 ms. Call changes: ddbc::AppendDiagRecords::SQLGetDiagRec_call (added, removed, or intermittent).
Row fetching in batches of 100: ddbc::SQLDescribeCol::driver_call +0.000 ms. Call changes: ddbc::AppendDiagRecords::SQLGetDiagRec_call (added, removed, or intermittent).
Row fetching in batches of 10,000: py::fetchmany::cpp_call +8.623 ms; ddbc::FetchMany_wrap +8.319 ms; ddbc::FetchBatchData::construct_rows +6.603 ms. Call changes: ddbc::AppendDiagRecords::SQLGetDiagRec_call (added, removed, or intermittent).
Joined aggregation queries: ddbc::FetchBatchData::cache_column_metadata +0.000 ms; py::execute::param_prep +0.000 ms; ddbc::SQLNumResultCols_wrap +0.000 ms. Call changes: ddbc::AppendDiagRecords::SQLGetDiagRec_call (added, removed, or intermittent).
Large joined-result fetching: ddbc::FetchBatchData::SQLFetchScroll_call +0.770 ms; py::execute::cpp_call +0.439 ms; ddbc::SQLExecDirect_wrap +0.430 ms. Call changes: ddbc::AppendDiagRecords::SQLGetDiagRec_call (added, removed, or intermittent).
1.2-million-row fetching: py::fetchall::cpp_call +3.544 ms; py::fetchall::row_wrap +1.796 ms; ddbc::FetchBatchData::SQLFetchScroll_call +1.366 ms. Call changes: ddbc::AppendDiagRecords::SQLGetDiagRec_call (added, removed, or intermittent).
Common table expression queries: ddbc::SQLDescribeCol::driver_call +0.000 ms; ddbc::SQLRowCount_wrap +0.000 ms; ddbc::SQLNumResultCols_wrap +0.000 ms. Call changes: ddbc::AppendDiagRecords::SQLGetDiagRec_call (added, removed, or intermittent).
256 KiB VARCHAR(MAX) / fetchall(): ddbc::FetchLobColumnData +0.048 ms; ddbc::SQLGetData_wrap +0.048 ms; ddbc::SQLNumResultCols_wrap +0.000 ms. Call changes: ddbc::AppendDiagRecords::SQLGetDiagRec_call (added, removed, or intermittent).
10,000 scalar values / fetchval() (debug disabled): ddbc::SQLDescribeCol::driver_call +0.000 ms. Call changes: ddbc::AppendDiagRecords::SQLGetDiagRec_call (added, removed, or intermittent).

Unix / SQL Server 2025

SELECT queries: ddbc::SQLBindColums +0.016 ms; py::execute::diag_records +0.001 ms; py::fetchall::row_wrap +0.000 ms. Call changes: ddbc::AppendDiagRecords::SQLGetDiagRec_call (added, removed, or intermittent).
Fetch-all queries: ddbc::SQLBindColums +0.005 ms; ddbc::FetchBatchData::cache_column_metadata +0.002 ms; ddbc::SQLNumResultCols_wrap +0.000 ms. Call changes: ddbc::AppendDiagRecords::SQLGetDiagRec_call (added, removed, or intermittent).
Row-by-row fetching: ddbc::SQLNumResultCols_wrap +0.005 ms; ddbc::SQLGetData_wrap +0.002 ms; ddbc::SQLDescribeCol::driver_call +0.000 ms. Call changes: ddbc::AppendDiagRecords::SQLGetDiagRec_call (added, removed, or intermittent).
Batched row fetching: py::fetchmany::cpp_call +2.077 ms; ddbc::FetchMany_wrap +1.371 ms; ddbc::FetchBatchData +1.262 ms. Call changes: ddbc::AppendDiagRecords::SQLGetDiagRec_call (added, removed, or intermittent).
Row fetching in batches of 100: py::fetchmany::cpp_call +9.171 ms; ddbc::FetchMany_wrap +8.892 ms; ddbc::FetchBatchData +8.439 ms. Call changes: ddbc::AppendDiagRecords::SQLGetDiagRec_call (added, removed, or intermittent).
Row fetching in batches of 10,000: ddbc::SQLBindColums +10.513 ms; py::fetchmany::cpp_call +5.395 ms; ddbc::FetchMany_wrap +5.099 ms. Call changes: ddbc::AppendDiagRecords::SQLGetDiagRec_call (added, removed, or intermittent).
Joined aggregation queries: py::execute::diag_records +0.000 ms; ddbc::SQLNumResultCols_wrap +0.000 ms; ddbc::SQLRowCount_wrap +0.000 ms. Call changes: ddbc::AppendDiagRecords::SQLGetDiagRec_call (added, removed, or intermittent).
Large joined-result fetching: ddbc::SQLBindColums +0.001 ms; ddbc::SQLRowCount_wrap +0.000 ms. Call changes: ddbc::AppendDiagRecords::SQLGetDiagRec_call (added, removed, or intermittent).

4 additional diagnostic rows are available in the raw ADO artifacts.

All database tasks and timings

Unix / SQL Server 2022

Database task	Before	After	Paired change	Result
Connection opening	10.231 ms	10.230 ms	+0.7%	no signal
SELECT queries	1.071 ms	1.006 ms	-7.5%	no signal
Row insertion	34.678 ms	34.413 ms	-1.7%	no signal
Executemany inserts	154.256 ms	157.395 ms	-0.6%	no signal
Fetch-all queries	120.322 ms	119.077 ms	+0.2%	no signal
Row-by-row fetching	14.475 ms	14.339 ms	-1.0%	no signal
Batched row fetching	116.042 ms	117.648 ms	+1.4%	no signal
Transaction commit and rollback	113.764 ms	115.136 ms	+1.2%	no signal
Arrow row fetching	93.735 ms	93.259 ms	+0.3%	no signal
100,000-row insertion	453.246 ms	440.312 ms	-3.3%	no signal
Row fetching in batches of 100	120.694 ms	119.523 ms	-0.2%	no signal
Row fetching in batches of 10,000	119.728 ms	130.632 ms	+1.0%	no signal
Repeated positional queries	33.777 ms	33.494 ms	-0.6%	no signal
Repeated named-parameter queries	36.070 ms	35.994 ms	-1.5%	no signal
Legacy 100,000-row insertion	353.743 ms	345.190 ms	-2.8%	no signal
Insertion with explicit input sizes	486.263 ms	488.204 ms	+0.2%	no signal
Joined aggregation queries	174.376 ms	173.459 ms	-0.1%	no signal
Large joined-result fetching	177.737 ms	176.059 ms	-1.7%	no signal
1.2-million-row fetching	3447.371 ms	3447.887 ms	-0.1%	no signal
Common table expression queries	5.403 ms	5.210 ms	-2.5%	no signal
256 KiB VARCHAR(MAX) / fetchall()	1.316 ms	1.285 ms	-7.4%	no signal
10,000 scalar values / fetchval() (debug disabled)	107.647 ms	105.982 ms	-1.9%	no signal

Unix / SQL Server 2025

Database task	Before	After	Paired change	Result
Connection opening	98.024 ms	98.880 ms	-0.4%	no signal
SELECT queries	1.050 ms	1.015 ms	-6.0%	no signal
Row insertion	33.569 ms	33.021 ms	-2.9%	no signal
Executemany inserts	154.042 ms	151.630 ms	-3.3%	no signal
Fetch-all queries	121.870 ms	120.986 ms	-0.2%	no signal
Row-by-row fetching	14.291 ms	14.259 ms	-1.3%	no signal
Batched row fetching	115.999 ms	117.795 ms	+2.0%	no signal
Transaction commit and rollback	109.758 ms	109.570 ms	+1.0%	no signal
Arrow row fetching	93.114 ms	94.272 ms	+1.2%	no signal
100,000-row insertion	460.981 ms	432.854 ms	-5.2%	no signal
Row fetching in batches of 100	119.963 ms	134.316 ms	+2.8%	no signal
Row fetching in batches of 10,000	133.269 ms	139.825 ms	+4.8%	no signal
Repeated positional queries	31.791 ms	31.680 ms	+0.1%	no signal
Repeated named-parameter queries	35.018 ms	34.721 ms	+0.2%	no signal
Legacy 100,000-row insertion	351.381 ms	353.008 ms	+0.1%	no signal
Insertion with explicit input sizes	476.560 ms	475.315 ms	-0.7%	no signal
Joined aggregation queries	167.753 ms	161.614 ms	-3.7%	no signal
Large joined-result fetching	191.645 ms	181.342 ms	-5.8%	no signal
1.2-million-row fetching	3570.568 ms	3602.229 ms	+0.0%	no signal
Common table expression queries	5.199 ms	5.054 ms	-4.0%	no signal
256 KiB VARCHAR(MAX) / fetchall()	1.482 ms	1.356 ms	-8.1%	no signal
10,000 scalar values / fetchval() (debug disabled)	105.939 ms	105.367 ms	-0.4%	no signal

Build and measurement details

ADO build 185781

PR head: 6fa455ea0ed38f8c497fa84aae788b3c289b3a70
Base: 185bc651fd2626aa4058de1be7658e52aad4c413
Measured merge: bdfadfba3be1de7bbdfd67252571ff4d2accf443

Unix / SQL Server 2022: Python 3.12.3, x86_64, SQL 16.0.4305.5; 5 paired comparisons and 1 warmup.
Unix / SQL Server 2025: Python 3.12.3, x86_64, SQL 17.0.5035.5; 5 paired comparisons and 1 warmup.

A consistent change requires more than 20% median paired movement, at least 1 ms between the median runtimes, and at least 80% of pairs exceeding the relative threshold in the same direction. A slowdown without enough pair agreement is reported as inconsistent.

The displayed change is the median of paired before-and-after ratios. It is not recalculated from the two displayed median runtimes.

Both revisions use profiling-enabled builds on the same agent and database, with alternating order and discarded warmups. Results are diagnostic and do not represent production-wheel latency.

Raw samples and logs are attached to the ADO run as profiler-* artifacts.

Copilot

Copilot review overview

🟡 Changes recommended

Unresolved critical cleanup, destructor, handle-lifecycle, and disconnect-synchronization issues block approval.

Get a fresh assessment by requesting another Copilot review.

Review effort: Lite
Findings: 4 · 1

Open (5)

Native connection handle remains attached after cleanup failure · New
Connection destructor can terminate on disconnect failure · New
Concurrent statement allocation races with connection disconnect · New
SQLFreeHandle failure incorrectly clears live handle · New
Returned connection can enter a replacement pool generation · New

What changed in this PR

Reverts PR #777 to restore prior pooled-connection behavior while retaining result-metadata invalidation.

Changes:

Removes pooled transaction sanitization and related regression tests.
Restores previous native connection, handle cleanup, and pool-return behavior.
Removes the reverted changelog entry.

File	Summary
`tests/test_009_pooling.py`	Removes pooling and native lifecycle regression tests.
`tests/test_006_exceptions.py`	Removes close-failure tests.
`mssql_python/pybind/ddbc_bindings.h`	Removes cleanup-state APIs.
`mssql_python/pybind/ddbc_bindings.cpp`	Restores earlier handle-management behavior.
`mssql_python/pybind/connection/connection.h`	Removes pool-sanitation interfaces.
`mssql_python/pybind/connection/connection.cpp`	Restores prior disconnect and pool-return behavior.
`mssql_python/pybind/connection/connection_pool.h`	Removes discard/origin-pool APIs.
`mssql_python/pybind/connection/connection_pool.cpp`	Restores key-based pool returns.
`mssql_python/connection.py`	Restores the previous close flow.
`CHANGELOG.md`	Removes the reverted fix entry.

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github-actions · 2026-09-25T16:38:04Z

📊 Code Coverage Report

🔥 Diff Coverage 80%	🎯 Overall Coverage 84%	📈 Total Lines Covered: `9552` out of `11239` 📁 Project: `mssql-python`

Diff Coverage

Diff: main...HEAD, staged and unstaged changes

mssql_python/connection.py (100%)
mssql_python/pybind/connection/connection.cpp (80.9%): Missing lines 291,310,331,354-355,375-376,482-486,490-491,658,711-712,723,775-780,804-805,952,1009,1011-1012
mssql_python/pybind/ddbc_bindings.cpp (80.0%): Missing lines 1593-1595,1678

Summary

Total: 178 lines
Missing: 34 lines
Coverage: 80%

mssql_python/pybind/connection/connection.cpp

Lines 287-295

  287 
  288 void Connection::commit() {
  289     PERF_TIMER("Connection::commit");
  290     _poolClean = false;
! 291     _poolSessionReset = false;
  292     if (!_dbcHandle) {
  293         ThrowStdException("Connection handle not allocated");
  294     }
  295     updateLastUsed();

Lines 306-314

  306 
  307 void Connection::rollback() {
  308     PERF_TIMER("Connection::rollback");
  309     _poolClean = false;
! 310     _poolSessionReset = false;
  311     if (!_dbcHandle) {
  312         ThrowStdException("Connection handle not allocated");
  313     }
  314     updateLastUsed();

Lines 327-335

  327     PERF_TIMER("Connection::setAutocommit");
  328     if (!enable) {
  329         _poolClean = false;
  330         _poolSessionReset = false;
! 331     }
  332     if (!_dbcHandle) {
  333         ThrowStdException("Connection handle not allocated");
  334     }
  335     clearResultMetadata();

Lines 350-359

  350         py::gil_scoped_release release;
  351         ret = SQLSetConnectAttr_ptr(_dbcHandle->get(), SQL_ATTR_AUTOCOMMIT,
  352                                     reinterpret_cast<SQLPOINTER>(static_cast<SQLULEN>(value)), 0);
  353     }
! 354     if (!SQL_SUCCEEDED(ret)) {
! 355         _poolClean = false;
  356         checkError(ret);
  357     }
  358     if (value == SQL_AUTOCOMMIT_ON) {
  359         LOG("Autocommit enabled");

Lines 371-380

  371     SQLINTEGER value;
  372     SQLINTEGER string_length;
  373     SQLRETURN ret = SQLGetConnectAttr_ptr(_dbcHandle->get(), SQL_ATTR_AUTOCOMMIT, &value,
  374                                           sizeof(value), &string_length);
! 375     if (!SQL_SUCCEEDED(ret)) {
! 376         _poolClean = false;
  377         checkError(ret);
  378     }
  379     return value == SQL_AUTOCOMMIT_ON;
  380 }

Lines 478-495

  478     }
  479 
  480     if (py::isinstance<py::int_>(value)) {
  481         // Get the integer value
! 482         int64_t longValue;
! 483         try {
! 484             longValue = value.cast<int64_t>();
! 485         } catch (const py::cast_error&) {
! 486             _poolProofDisabled = true;
  487             throw;
  488         } catch (const py::error_already_set&) {
  489             _poolProofDisabled = true;
! 490             throw;
! 491         }
  492         if (scalarLoginTimeout &&
  493             (longValue < 0 ||
  494              static_cast<uint64_t>(longValue) > std::numeric_limits<SQLUINTEGER>::max())) {
  495             _poolProofDisabled = true;

Lines 654-662

  654 bool Connection::reset() {
  655     if (!_dbcHandle) {
  656         ThrowStdException("Connection handle not allocated");
  657     }
! 658     if (_cleanupState->childFreeFailed) {
  659         _poolClean = false;
  660         _poolSessionReset = false;
  661         LOG("Cannot reuse connection after a statement handle failed to free");
  662         return false;

Lines 707-716

  707         LOG("Failed to reset transaction isolation level (ret=%d). Marking as dead.", ret);
  708         return false;
  709     }
  710 
! 711     // A retained child can finish cleanup while either attribute call releases the GIL.
! 712     if (_cleanupState->childFreeFailed) {
  713         _poolClean = false;
  714         _poolSessionReset = false;
  715         LOG("Cannot reuse connection after a statement handle failed to free");
  716         return false;

Lines 719-727

  719     return true;
  720 }
  721 
  722 void Connection::prepareForPool() {
! 723     PERF_TIMER("Connection::prepareForPool");
  724     if (!_dbcHandle) {
  725         ThrowStdException("Connection handle not allocated");
  726     }
  727     if (_cleanupState->childFreeFailed) {

Lines 771-784

  771                                             reinterpretU16stringAsSqlWChar(rollbackQuery), SQL_NTS);
  772                     if (!SQL_SUCCEEDED(ret)) {
  773                         ErrorInfo error = SQLReadError(SQL_HANDLE_STMT, statement, ret);
  774                         statementError = error.sqlState.length() == 5
! 775                             ? "SQLSTATE:" + error.sqlState + ":" + error.ddbcErrorMsg
! 776                             : error.ddbcErrorMsg;
! 777                     }
! 778                     SQLRETURN freeRet = SQLFreeHandle_ptr(SQL_HANDLE_STMT, statement);
! 779                     if (SQL_SUCCEEDED(ret) && !SQL_SUCCEEDED(freeRet)) {
! 780                         ErrorInfo error = SQLReadError(SQL_HANDLE_STMT, statement, freeRet);
  781                         statementError = error.sqlState.length() == 5
  782                             ? "SQLSTATE:" + error.sqlState + ":" + error.ddbcErrorMsg
  783                             : error.ddbcErrorMsg;
  784                         ret = freeRet;

Lines 800-809

  800     }
  801     if (!statementError.empty()) {
  802         ThrowStdException(statementError);
  803     }
! 804     checkError(ret);
! 805     // A weak_ptr expires before its destructor finishes. Read the count before
  806     // the failure latch so a completed destructor cannot hide a failed native free.
  807     const bool noChildren = _cleanupState->childStatementCount == 0;
  808     if (_cleanupState->childFreeFailed) {
  809         ThrowStdException("Cannot pool connection after a statement handle failed to free");

Lines 948-956

  948         // SQLDisconnect failure using the existing connection and children.
  949         if (!_usePool && !rollbackBeforeDisconnect) {
  950             throw;
  951         }
! 952         // Never retain a connection whose transaction state could not be
  953         // sanitized. Release capacity and preserve the original cleanup error.
  954         try {
  955             ConnectionPoolManager::getInstance().discardConnection(_originPool, _conn);
  956         } catch (...) {

Lines 1005-1016

  1005     return conn->allocStatementHandle();
  1006 }
  1007 
  1008 py::object Connection::getInfo(SQLUSMALLINT infoType) const {
! 1009     _poolClean = false;
  1010     _poolSessionReset = false;
! 1011     if (infoType == SQL_DRIVER_HDBC || infoType == SQL_DRIVER_HENV ||
! 1012         infoType == SQL_DRIVER_HSTMT || infoType == SQL_DRIVER_HLIB) {
  1013         _poolProofDisabled = true;
  1014     }
  1015     if (!_dbcHandle) {
  1016         ThrowStdException("Connection handle not allocated");

mssql_python/pybind/ddbc_bindings.cpp

Lines 1589-1599

  1589 
  1590 // SqlHandle definition
  1591 SqlHandle::SqlHandle(SQLSMALLINT type, SQLHANDLE rawHandle,
  1592                      std::shared_ptr<ConnectionCleanupState> cleanupState)
! 1593     : _type(type), _handle(rawHandle), _cleanupState(std::move(cleanupState)) {
! 1594     if (_type == SQL_HANDLE_STMT && _cleanupState) {
! 1595         ++_cleanupState->childStatementCount;
  1596     }
  1597 }
  1598 
  1599 SqlHandle::~SqlHandle() {

Lines 1674-1682

  1674         if (_implicitly_freed || (_cleanupState && _cleanupState->disconnected)) {
  1675             _handle = nullptr;
  1676             return SQL_SUCCESS;
  1677         }
! 1678         SQLRETURN ret = SQLFreeHandle_ptr ? SQLFreeHandle_ptr(_type, _handle) : SQL_INVALID_HANDLE;
  1679         if (SQL_SUCCEEDED(ret)) {
  1680             _handle = nullptr;
  1681         } else if (_type == SQL_HANDLE_STMT && _cleanupState) {
  1682             _cleanupState->childFreeFailed = true;

📋 Files Needing Attention

📉 Files with overall lowest coverage (click to expand)

mssql_python.pybind.performance_counter.hpp: 0.7%
mssql_python.pybind.logger_bridge.cpp: 57.9%
mssql_python.pybind.ddbc_bindings.h: 62.6%
mssql_python.pybind.logger_bridge.hpp: 70.8%
mssql_python.pybind.connection.connection.cpp: 81.4%
mssql_python.pybind.connection.connection_pool.cpp: 82.3%
mssql_python.logging.py: 86.2%
mssql_python.pooling.py: 90.1%
mssql_python.pybind.fetch_temporal.hpp: 92.1%
mssql_python.cursor.py: 92.5%

🔗 Quick Links

⚙️ Build Summary	📋 Coverage Details
View Azure DevOps Build	Browse Full Coverage Report

Replace the PR 777 revert with conservative clean-state tracking and consolidated native sanitation. Used or uncertain connections still roll back before parking; only previously sanitized unused connections can skip cleanup. Preserve scalar login timeouts without trusting arbitrary attributes. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Copilot

Copilot review overview

🟡 Changes recommended

Native tests are not part of standard validation, and exception tests no longer cover the failure paths their names describe.

Get a fresh assessment by requesting another Copilot review.

Review effort: Lite
Findings: 2

Open (2)

Opt-in native tests are excluded from standard CI · New
Rollback failure test no longer exercises rollback failure · New

Resolved since last review (5)

SQLFreeHandle failure incorrectly clears live handle
Concurrent statement allocation races with connection disconnect
Connection destructor can terminate on disconnect failure
Native connection handle remains attached after cleanup failure
Returned connection can enter a replacement pool generation

Copilot

Copilot review overview

🔵 Needs a closer look

Enable the native sanitation regression suite in normal CI.

Review effort: Lite
Findings: 2

Open (2)

Rollback failure test no longer exercises rollback failure
Opt-in native tests are excluded from standard CI

Replace redundant autocommit transitions with a reset-triggered rollback batch and preserve proof so checkout can skip duplicate session reset work. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Copilot

Copilot review overview

🔵 Needs a closer look

Address the manual-lease state bug, restore Python-boundary failure coverage, and run native sanitation tests in CI.

Review effort: Lite
Findings: 2

Open (2)

Rollback failure test no longer exercises rollback failure
Opt-in native tests are excluded from standard CI

Previously missed (1)

In code that hasn't changed since last review

Autocommit read failure coverage was removed

tests/test_006_exceptions.py:304

This replacement likewise removes the simulated get_autocommit failure, so the test named test_close_cleans_up_after_autocommit_read_failure no longer covers that error path. Because the probe now runs inside native close, add a Python-boundary test that can inject/observe a native probe failure, or rename this test so the suite does not falsely claim coverage it no longer provides.

Preserve native sanitation proof and original diagnostic enumeration on uncertain header results. Add deterministic ODBC-call and diagnostic-preservation regression coverage. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Copilot

Copilot review overview

🟡 Changes recommended

Unresolved raw-handle cleanup and validation/test consistency issues must be addressed.

Review effort: Lite
Findings: 1 · 2

Open (3)

Untracked failed statement cleanup leaks discarded connections · New
Rollback failure test no longer exercises rollback failure
Opt-in native tests are excluded from standard CI

Teach the mixed-diagnostic interceptor the SQL_DIAG_NUMBER header contract while retaining SQLSTATE and message assertions. Run the existing native sanitation CTest target as a blocking job in standard PR validation. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Copilot

🔵 Needs a closer look

Moderate cleanup ownership and session-reset state issues remain unresolved.

3 open findings

Untracked failed statement cleanup leaks discarded connections
Rollback failure test no longer exercises rollback failure
Opt-in native tests are excluded from standard CI

🧠 Review effort: Lite

…60925

Copilot

🔵 Needs a closer look

A critical native handle-lifetime cleanup issue remains unresolved, with broader validation still pending.

1 open finding

Failed child frees can incorrectly mark the connection clean · New

4 resolved since last review

🧠 Review effort: Lite

…60925

Copilot

🔵 Needs a closer look

Unresolved native handle-lifetime and rollback-failure coverage concerns require changes and human review.

1 open finding

Failed child frees can incorrectly mark the connection clean

🧠 Review effort: Lite

Preserve failed statement frees beyond wrapper destruction and reject affected connections on check-in and checkout. Count child lifetimes through cleanup completion before enabling the clean fast path. Cover orphan reclamation, retained aliases, cleanup races, and pool capacity recovery. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Copilot

🔵 Needs a closer look

A moderate failure-path coverage gap remains, diagnostic behavior needs documentation and validation, and broader validation is pending.

0 open findings

1 resolved since last review

Failed child frees can incorrectly mark the connection clean

🧠 Review effort: Lite

…60925

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🔵 Needs a closer look

Native rollback and autocommit-read failure coverage remain unresolved, with broader validation still pending.

0 open findings

🧠 Review effort: Lite

…60925

Copilot

🔵 Needs a closer look

A moderate temporary-handle cleanup issue and misleading failure-test naming remain unresolved.

0 open findings

🧠 Review effort: Lite

…60925

Copilot

🟡 Changes recommended

A critical native handle-lifetime race remains in the temporary check-in statement sequence and must be serialized or tracked safely before approval.

1 open issue

Serialize temporary statement handle lifecycle under cleanup mutex · New

_{Review effort: Lite}

+                SQLHANDLE statement = nullptr;
+                ret = SQLAllocHandle_ptr(SQL_HANDLE_STMT, _dbcHandle->get(), &statement);
+                if (SQL_SUCCEEDED(ret)) {
+                    const std::u16string rollbackQuery =
+                        u"IF @@TRANCOUNT > 0 ROLLBACK TRANSACTION; "


Copilot AI lite review requested due to automatic review settings September 25, 2026 16:30

github-actions Bot added the pr-size: large Substantial code update label Sep 25, 2026

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Copilot AI review requested due to automatic review settings September 25, 2026 19:11

Sumit Sarabhai (sumitmsft) changed the title ~~PERF: Revert pooled connection cleanup from PR #777~~ PERF: Optimize pooled connection return while preserving transaction safety Sep 25, 2026

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Comment thread tests/native/pool_sanitation.cpp Fixed

STYLE: Format pooling timeout regression assertion

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Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

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Comment thread mssql_python/pybind/CMakeLists.txt

Comment thread tests/test_006_exceptions.py

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PERF: Reduce pooled connection cleanup overhead

e7444e7

Replace redundant autocommit transitions with a reset-triggered rollback batch and preserve proof so checkout can skip duplicate session reset work. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

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Comment thread mssql_python/pybind/connection/connection.cpp

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Merge branch 'main' into sumitmsft/revert-777-pooling-performance-202…

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Comment thread mssql_python/pybind/connection/connection.cpp Outdated

Merge branch 'main' into sumitmsft/revert-777-pooling-performance-202…

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Jahnvi Thakkar (jahnvi480) approved these changes Oct 13, 2026

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Merge branch 'main' into sumitmsft/revert-777-pooling-performance-202…

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…60925

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Gaurav Sharma (bewithgaurav) approved these changes Oct 13, 2026

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Comment thread eng/pipelines/pr-validation-pipeline.yml

Merge branch 'main' into sumitmsft/revert-777-pooling-performance-202…

04e13fd

…60925

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Sumit Sarabhai (sumitmsft) disabled auto-merge October 13, 2026 10:31

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Merge branch 'main' into sumitmsft/revert-777-pooling-performance-202…

6fa455e

…60925

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Conversation

Sumit Sarabhai (sumitmsft) commented Sep 25, 2026 • edited by azure-boards Bot Loading Uh oh! There was an error while loading. Please reload this page.

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Summary

Scope and limitations

Validation

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PR Performance Report

✅ No regression detected

Unix / SQL Server 2022

Unix / SQL Server 2025

Unix / SQL Server 2022

Unix / SQL Server 2025

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Copilot review overview

🟡 Changes recommended

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📊 Code Coverage Report

🔥 Diff Coverage

80%

🎯 Overall Coverage

84%

Diff Coverage

Diff: main...HEAD, staged and unstaged changes

Summary

mssql_python/pybind/connection/connection.cpp

mssql_python/pybind/ddbc_bindings.cpp

📋 Files Needing Attention

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🟡 Changes recommended

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🟡 Changes recommended

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Sumit Sarabhai (sumitmsft) commented Sep 25, 2026 •

edited by azure-boards Bot

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