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Remove multiplexing - #6457
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Remove multiplexing#6457
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Pull request overview
This PR removes the multiplexing feature from Npgsql and simplifies the implementation and test suite accordingly (per #6449, intended to merge after #6314).
Changes:
- Removes multiplexing implementation, configuration surface area, and related infrastructure (data source, connector I/O loops, binding scopes, counters, logging).
- Updates tests to run without
MultiplexingTestBase/MultiplexingModeand deletes multiplexing-only test cases/workarounds. - Updates public API tracking to reflect the removal of
NpgsqlConnectionStringBuilder.MultiplexingandWriteCoalescingBufferThresholdBytes.
Reviewed changes
Copilot reviewed 67 out of 67 changed files in this pull request and generated 1 comment.
Show a summary per file
| File | Description |
|---|---|
| test/Npgsql.Tests/Types/TextTests.cs | Switches from multiplexing fixtures/base class to TestBase. |
| test/Npgsql.Tests/Types/RecordTests.cs | Switches from multiplexing fixtures/base class to TestBase. |
| test/Npgsql.Tests/Types/RangeTests.cs | Removes multiplexing workarounds; switches to TestBase. |
| test/Npgsql.Tests/Types/NumericTypeTests.cs | Switches from multiplexing fixtures/base class to TestBase. |
| test/Npgsql.Tests/Types/NumericTests.cs | Switches from multiplexing fixtures/base class to TestBase. |
| test/Npgsql.Tests/Types/NetworkTypeTests.cs | Switches from multiplexing fixtures/base class to TestBase. |
| test/Npgsql.Tests/Types/MultirangeTests.cs | Removes multiplexing deadlock workaround (Task.Yield). |
| test/Npgsql.Tests/Types/MiscTypeTests.cs | Removes multiplexing skip/branching in tests; switches to TestBase. |
| test/Npgsql.Tests/Types/LegacyDateTimeTests.cs | Removes multiplexing-specific comment/import; remains non-parallelizable. |
| test/Npgsql.Tests/Types/LTreeTests.cs | Switches from multiplexing fixtures/base class to TestBase. |
| test/Npgsql.Tests/Types/JsonTests.cs | Removes multiplexing fixtures and constructor parameter; keeps json/jsonb fixtures. |
| test/Npgsql.Tests/Types/JsonPathTests.cs | Switches from multiplexing fixtures/base class to TestBase. |
| test/Npgsql.Tests/Types/JsonDynamicTests.cs | Removes multiplexing fixtures and constructor parameter; keeps json/jsonb fixtures. |
| test/Npgsql.Tests/Types/InternalTypeTests.cs | Switches from multiplexing fixtures/base class to TestBase. |
| test/Npgsql.Tests/Types/HstoreTests.cs | Switches from multiplexing fixtures/base class to TestBase. |
| test/Npgsql.Tests/Types/GeometricTypeTests.cs | Switches from multiplexing fixtures/base class to TestBase. |
| test/Npgsql.Tests/Types/FullTextSearchTests.cs | Switches from multiplexing fixtures/base class to TestBase. |
| test/Npgsql.Tests/Types/EnumTests.cs | Switches from multiplexing fixtures/base class to TestBase. |
| test/Npgsql.Tests/Types/DomainTests.cs | Removes multiplexing ignore and switches to TestBase. |
| test/Npgsql.Tests/Types/DateTimeTests.cs | Removes multiplexing-specific comment. |
| test/Npgsql.Tests/Types/CubeTests.cs | Switches to TestBase and removes multiplexing ctor. |
| test/Npgsql.Tests/Types/CompositeTests.cs | Removes multiplexing-specific transaction workaround; updates comments. |
| test/Npgsql.Tests/Types/ByteaTests.cs | Switches from multiplexing fixtures/base class to TestBase. |
| test/Npgsql.Tests/Types/BitStringTests.cs | Switches from multiplexing fixtures/base class to TestBase. |
| test/Npgsql.Tests/Types/ArrayTests.cs | Removes multiplexing ignores and switches to TestBase. |
| test/Npgsql.Tests/TransactionTests.cs | Removes multiplexing branches/ignores; switches to TestBase. |
| test/Npgsql.Tests/TracingTests.cs | Removes multiplexing fixture dimension; simplifies activity assertions to single mode. |
| test/Npgsql.Tests/TestUtil.cs | Removes Multiplexing=False from default test connection string. |
| test/Npgsql.Tests/Support/TestBase.cs | Removes multiplexing mentions and multiplexing-specific tx usage in type assertion helpers. |
| test/Npgsql.Tests/Support/MultiplexingTestBase.cs | Deleted multiplexing test base and MultiplexingMode enum. |
| test/Npgsql.Tests/Support/AssemblySetUp.cs | Removes Multiplexing=false from admin connection settings. |
| test/Npgsql.Tests/SecurityTests.cs | Removes multiplexing parameter dimension and related branching. |
| test/Npgsql.Tests/ReaderTests.cs | Removes multiplexing fixtures/branches/workarounds; simplifies ctor. |
| test/Npgsql.Tests/ReaderOldSchemaTests.cs | Removes commented multiplexing-specific guard. |
| test/Npgsql.Tests/ReaderNewSchemaTests.cs | Removes commented multiplexing ignore. |
| test/Npgsql.Tests/PrepareTests.cs | Removes multiplexing-not-supported test now that feature is removed. |
| test/Npgsql.Tests/PoolTests.cs | Removes multiplexing-only ignored test. |
| test/Npgsql.Tests/LoggingTests.cs | Removes multiplexing branching in logging assertions; switches to TestBase. |
| test/Npgsql.Tests/DataSourceTests.cs | Removes multiplexing dimension; removes multiplexing-specific regression test. |
| test/Npgsql.Tests/CopyTests.cs | Removes multiplexing ignores and updates comments; switches to TestBase. |
| test/Npgsql.Tests/ConnectionTests.cs | Removes multiplexing branches/ignores; switches to TestBase. |
| test/Npgsql.Tests/CommandTests.cs | Removes multiplexing branches/ignores; switches to TestBase. |
| test/Npgsql.Tests/CommandParameterTests.cs | Removes multiplexing branch for prepared parameter test; switches to TestBase. |
| test/Npgsql.Tests/BugTests.cs | Removes multiplexing-only regression test. |
| test/Npgsql.Tests/BatchTests.cs | Removes multiplexing fixture dimension; switches to TestBase. |
| test/Npgsql.Tests/AuthenticationTests.cs | Removes multiplexing-specific connection retry comment; switches to TestBase. |
| test/Npgsql.PluginTests/NodaTimeTests.cs | Switches from multiplexing test base to TestBase; removes multiplexing ctor. |
| src/Npgsql/Util/ManualResetValueTaskSource.cs | Deleted helper type used by multiplexing paths. |
| src/Npgsql/Replication/ReplicationConnection.cs | Removes multiplexing references and disables it implicitly by removal. |
| src/Npgsql/PublicAPI.Unshipped.txt | Marks multiplexing-related connection string builder properties as removed. |
| src/Npgsql/PoolingDataSource.cs | Removes multiplexing-specific asserts/comments around idle connectors and return path. |
| src/Npgsql/NpgsqlTransaction.cs | Removes transaction binding-scope unbinding (multiplexing-related). |
| src/Npgsql/NpgsqlSlimDataSourceBuilder.cs | Removes construction and validation logic for multiplexing data source. |
| src/Npgsql/NpgsqlSchema.cs | Removes temporary binding scope; uses bound connector directly for DataTypes schema. |
| src/Npgsql/NpgsqlRawCopyStream.cs | Removes binding-scope teardown (multiplexing-related). |
| src/Npgsql/NpgsqlMultiHostDataSource.cs | Removes multiplexing assertion in multi-host setup. |
| src/Npgsql/NpgsqlEventSource.cs | Removes multiplexing-specific counters and tracking. |
| src/Npgsql/NpgsqlEventId.cs | Leaves multiplexing-related event IDs but annotates them as removed feature. |
| src/Npgsql/NpgsqlDataReader.cs | Removes multiplexing-specific cleanup/unbinding behavior; simplifies send-task comment. |
| src/Npgsql/NpgsqlConnectionStringBuilder.cs | Removes Multiplexing and WriteCoalescingBufferThresholdBytes settings and validation. |
| src/Npgsql/NpgsqlConnection.cs | Removes connector binding scope infrastructure and multiplexing open/close paths. |
| src/Npgsql/NpgsqlCommand.cs | Removes multiplexing execution branch and related channel/value-task plumbing; simplifies query parsing. |
| src/Npgsql/NpgsqlBinaryImporter.cs | Removes binding-scope teardown (multiplexing-related). |
| src/Npgsql/NpgsqlBinaryExporter.cs | Removes binding-scope teardown (multiplexing-related). |
| src/Npgsql/MultiplexingDataSource.cs | Deleted multiplexing data source implementation. |
| src/Npgsql/LogMessages.cs | Removes multiplexing-specific log messages and event usage. |
| src/Npgsql/Internal/NpgsqlConnector.cs | Removes multiplexing I/O loops, command-in-flight tracking, and multiplexing-only restrictions. |
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NinoFloris
approved these changes
Feb 27, 2026
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It all looks good to me. Always possible the PR left some traces behind, but that's not really important to one shot either.
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Pull request overview
Copilot reviewed 67 out of 67 changed files in this pull request and generated 2 comments.
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Comment on lines
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| [Test] | ||
| [IssueLink("https://github.com/npgsql/npgsql/issues/3248")] | ||
| // More at #3254 | ||
| public async Task Bug3248_Dispose_transaction_Rollback() | ||
| { | ||
| if (!IsMultiplexing) | ||
| return; | ||
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| using var conn = await OpenConnectionAsync(); | ||
| await using (var tx = await conn.BeginTransactionAsync()) | ||
| { | ||
| Assert.That(conn.Connector, Is.Not.Null); | ||
| Assert.That(async () => await conn.ExecuteScalarAsync("SELECT * FROM \"unknown_table\"", tx: tx), | ||
| Throws.Exception.TypeOf<PostgresException>()); | ||
| Assert.That(conn.Connector, Is.Not.Null); | ||
| } | ||
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| Assert.That(conn.Connector, Is.Null); | ||
| } |
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Bug3248_Dispose_transaction_Rollback is now an empty async test method, so it will always pass without exercising anything. Either remove this test entirely (if the scenario was multiplexing-only) or reintroduce a non-multiplexing assertion that reproduces #3248 so the regression remains covered.
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| [Test] | ||
| [IssueLink("https://github.com/npgsql/npgsql/issues/3248")] | ||
| // More at #3254 | ||
| public async Task Bug3248_Dispose_connection_Rollback() | ||
| { | ||
| if (!IsMultiplexing) | ||
| return; | ||
|
|
||
| var conn = await OpenConnectionAsync(); | ||
| var tx = conn.BeginTransaction(); | ||
| Assert.That(conn.Connector, Is.Not.Null); | ||
| Assert.That(async () => await conn.ExecuteScalarAsync("SELECT * FROM \"unknown_table\"", tx: tx), | ||
| Throws.Exception.TypeOf<PostgresException>()); | ||
| Assert.That(conn.Connector, Is.Not.Null); | ||
|
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| await conn.DisposeAsync(); | ||
| Assert.That(conn.Connector, Is.Null); | ||
| } |
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Bug3248_Dispose_connection_Rollback is now an empty async test method, so it will always pass and no longer protects against regressions. Please delete it or rewrite it to validate the intended rollback/dispose behavior in the non-multiplexing code path.
This was referenced Mar 14, 2026
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Move API changes from commits after v10.0.0 back to Unshipped, as they represent 11.0 work, not 10.0: - Remove multiplexing (#6457): 4 *REMOVED* entries - Remove large object API (#6493): 37 *REMOVED* entries - Add back parameterless ReloadTypesAsync (#6522): undo the v10.0 addition of CancellationToken overload and re-add the parameterless overload Also adjusts Shipped to correctly reflect the v10.0.0 public API. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
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added a commit
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Apr 4, 2026
Move API changes from commits after v10.0.0 back to Unshipped, as they represent 11.0 work, not 10.0: - Remove multiplexing (#6457): 4 *REMOVED* entries - Remove large object API (#6493): 37 *REMOVED* entries - Add back parameterless ReloadTypesAsync (#6522): undo the v10.0 addition of CancellationToken overload and re-add the parameterless overload Also adjusts Shipped to correctly reflect the v10.0.0 public API. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
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Since this has been merged, I don't think there's a point in opening an issue about this, but I just wanted to mention that I ran into a regular-ish (every 2-14 days) presumed race condition with multiplexing enabled where all database operations time out and a collected dotnet trace shows the multiplexer spinwait. So maybe there's more than just performance considerations for removing this after all ;) 
Fixed by adding a PGBouncer in transaction mode and disabling multiplexing. Cheers! |
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Merge only after #6314.
Closes #6449