Handle out-of-order split-include rows to prevent child collection loss under concurrent inserts

[Copilot]

AsSplitQuery collection includes can drop valid children when a concurrent insert introduces unrelated parent/child rows between split queries. The current stitching path stops at the first non-matching child row, even when matching rows for the current parent still appear later in the ordered stream.

• Materialization fix (split include path)

  • Updated split include population (PopulateSplitIncludeCollection / async variant) to distinguish:
    • next-parent boundary (should stop and hand off), vs.
    • out-of-order unrelated row caused by concurrent insert (should skip and continue).
  • Sort direction is now detected at compile time in SelectExpression.GetParentIdentifierSortOrder: checks whether the leading ORDER BY columns exactly match the parent identifier (PK) columns and returns 1 (ascending), -1 (descending), or null (unknown/non-PK order — skipping disabled).
  • ParentIdentifierSortOrder is stored in RelationalSplitCollectionShaperExpression and passed as a compile-time constant into PopulateSplitIncludeCollection at code generation time, avoiding the flawed runtime inference approach.
  • Added comparable-identifier fallback logic (TryCompareIdentifiers) to safely detect relative ordering without changing key equality semantics.

• Regression coverage

  • Added a relational ad-hoc split-query test reproducing the issue pattern:
    • load parents with Include(...).AsSplitQuery().OrderByDescending(...)
    • inject concurrent unrelated entity+children during materialization
    • assert existing parents still get their full child collections.

if (!CompareIdentifiers(identifierValueComparers, parentIdentifier, currentChildIdentifier))
{
    if (ShouldSkipOutOfOrderChild(dataReaderContext, parentIdentifier, currentChildIdentifier))
    {
        dataReaderContext.HasNext = null; // consume unrelated row and keep scanning
        continue;
    }

    dataReaderContext.HasNext = true; // reached boundary for another parent
    return;
}

[Copilot]

Pull request overview

This pull request addresses a split-query (AsSplitQuery) include materialization edge case where child rows can be skipped when concurrent inserts cause “out-of-order” rows to appear in the streamed results. The fix adds lightweight state to the split include data-reader context and adjusts the stitching loop to skip unrelated out-of-order rows while still detecting true next-parent boundaries. A regression test reproduces the concurrency pattern and asserts child collections are fully populated.

Changes:

• Update split-include collection population (sync/async) to detect and skip out-of-order unrelated child rows instead of prematurely stopping.
• Add per-reader state (PreviousParentIdentifier, inferred parent sort direction) to support the new boundary/skip decision.
• Add an ad-hoc relational split-query regression test covering concurrent insertion during materialization.

Reviewed changes

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

File	Description
test/EFCore.Relational.Specification.Tests/Query/AdHocQuerySplittingQueryTestBase.cs	Adds a regression test reproducing child collection loss under concurrent inserts with split include + descending order.
src/EFCore.Relational/Query/RelationalShapedQueryCompilingExpressionVisitor.ShaperProcessingExpressionVisitor.ClientMethods.cs	Implements out-of-order row skip logic and sort-direction inference used by split include stitching.
src/EFCore.Relational/Query/Internal/SplitQueryDataReaderContext.cs	Adds new per-reader fields used to infer/track identifier ordering during split include population.

[AndriySvyryd]

@copilot Fix this file

[Copilot]

Fixed. The TryGetNonEntityNullabilityMarker and RemapNonEntityNullabilityMarker methods had been moved to SelectExpression.Helper.cs but the originals were left in SelectExpression.cs, causing a duplicate-member build error. Removed the duplicates from SelectExpression.cs in commit $(git rev-parse --short HEAD).

[Copilot]

Fixed in e806636. The TryGetNonEntityNullabilityMarker and RemapNonEntityNullabilityMarker methods were moved to SelectExpression.Helper.cs but the originals were left in SelectExpression.cs, causing a duplicate-member build error. Removed the duplicates from SelectExpression.cs.