Preserve discriminating ORDER BY for many-to-many collections

[Copilot]

Many-to-many collection includes could omit their only varying identifier from ORDER BY, making materialization order depend on the provider’s physical access path.

• Ordering logic

  • Retain the pending identifier when surviving identifiers only repeat the collection join key.
  • Preserve the existing omission when another identifier already discriminates collection elements.

• Regression coverage

  • Seed SQLite join rows out of key order to expose physical-order dependencies.
  • Update SQL Server baselines to include the restored discriminator.

-- Before
ORDER BY [e].[Id], [s].[OneId]

-- After
ORDER BY [e].[Id], [s].[OneId], [s].[TwoId]

• Fixes Many-to-many collection ORDER BY loses its only discriminating column (regression in 11.0) #38770

[Copilot]

Pull request overview

Fixes nondeterministic many-to-many collection materialization by retaining the final discriminating identifier in generated ORDER BY clauses.

Changes:

• Detects when surviving orderings contain only collection join keys.
• Seeds SQLite join rows out of key order for regression coverage.
• Updates SQL Server baselines across standard, temporal, TPT, and TPC queries.

Reviewed changes

Copilot reviewed 6 out of 6 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
src/EFCore.Relational/Query/SqlExpressions/SelectExpression.cs	Preserves the required collection discriminator ordering.
test/EFCore.Sqlite.FunctionalTests/ManyToManyLoadSqliteTestBase.cs	Introduces non-key-ordered join rows.
test/EFCore.SqlServer.FunctionalTests/Query/ManyToManyQuerySqlServerTest.cs	Updates SQL ordering baselines.
test/EFCore.SqlServer.FunctionalTests/Query/TemporalManyToManyQuerySqlServerTest.cs	Updates temporal SQL baselines.
test/EFCore.SqlServer.FunctionalTests/Query/Inheritance/TPTManyToManyQuerySqlServerTest.cs	Updates TPT SQL baselines.
test/EFCore.SqlServer.FunctionalTests/Query/Inheritance/TPCManyToManyQuerySqlServerTest.cs	Updates TPC SQL baselines.

---

💡 Add a code-review agent skill for context-aware, tailored reviews. Learn more in the docs.