Fix ValuesExpression pruning dropping outer columns referenced from VALUES cells

[yvesleguennec]

Fixes #38700

SqlTreePruner.PruneValues (from #36159) copied VALUES row cells without
Visit(), so ColumnExpressions embedded in inline collections were never
registered. Outer join projections were then over-pruned (e.g. only Id
projected while EXISTS still referenced ServiceId).

Fix

• Always Visit() nested RowValues / ValuesParameter in PruneValues
  (same pattern as OpenJSON pruning)
• Fix column-name backfill to use ColumnNames[j] instead of repeating the
  first unreferenced column's name

Tests

• Relational AdHoc query filters regression for the reported scenario
• SqlServer SQL baseline asserting ServiceId remains in the join projection

Note: approach described on #38700; no maintainer reply after ~1.5 weeks, opening PR for review.

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[yvesleguennec]

@dotnet-policy-service agree

[Copilot]

Pull request overview

Fixes VALUES pruning so nested outer-column references are retained.

Changes:

• Visits VALUES cells during pruning.
• Corrects pruned column-name backfilling.
• Adds relational regression coverage and a SQL Server baseline.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 1 comment.

File	Description
src/EFCore.Relational/Query/SqlTreePruner.cs	Corrects VALUES traversal and column pruning.
test/EFCore.Relational.Specification.Tests/Query/AdHocQueryFiltersQueryRelationalTestBase.cs	Adds the regression scenario.
test/EFCore.SqlServer.FunctionalTests/Query/AdHocQueryFiltersQuerySqlServerTest.cs	Verifies the generated SQL projection.

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[AndriySvyryd]

Unit tests for query code aren't very useful. Try to find a real query that hits this case

[yvesleguennec]

Thanks — agreed that a unit test isn’t the right way to cover query behavior here.

To clarify scope on the secondary change and that test:

This PR’s fix for #38700 is visiting nested RowValues / ValuesParameter in PruneValues, so ColumnExpressions embedded in inline VALUES cells get registered before outer join projections are pruned. That path is covered by the relational AdHoc query-filter regression (the original repro).

Separately, in the same method, the loop that backfills leading column names when a later column is pruned was using the pruned column’s name instead of each surviving leading name (ColumnNames[j]). That’s a real correctness bug in the pruned ColumnNames list (misaligned names vs kept values). The same backfill pattern is already correct for OpenJSON in SqlServerSqlTreePruner. I noticed it while reading PruneValues for that bug; I never hit it via a customer query, but I’m keeping the one-liner because it’s still a bug.

Copilot asked for coverage of that backfill path. I added a synthetic unit test for it; given your feedback, I’ll drop that test rather than inventing an artificial LINQ scenario for a case that doesn’t show up in normal _ord-first VALUES pruning.