C#: Disable dynamic reordering for Unification::Gvn::unifiableTypeArguments - #22491
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kaspersv merged 1 commit intoSep 2, 2026
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🟢 Approval recommended
The focused pragma change directly implements the stated performance workaround without altering predicate semantics.
Review tier: Balanced
Findings: None
What changed in this PR
Disables dynamic join ordering for a C# unification predicate to prevent the reported EF Core performance regression.
Changes:
- Adds
no_dynamic_join_ordertoUnification::Gvn::unifiableTypeArguments.
| File | Description |
|---|---|
csharp/ql/lib/semmle/code/csharp/Unification.qll |
Applies the targeted join-ordering override. |
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hvitved
approved these changes
Sep 2, 2026
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We are working on a new dynamic join orderer for CodeQL that join orders predicates at evaluation-time using run-time cardinality information instead of relying on a statically chosen join order decided at compilation-time. At the moment the
Unification::Gvn::unifiableTypeArgumentspredicate is join ordered badly by the dynamic join orderer, leading to a catastrophic join regression forefcore. This PR disables dynamic join ordering for this particular predicate, while we work on improving the dynamic join orderer.Dynamic join ordering is still disabled by default during compilation and evaluation and the
no_dynamic_join_orderpragma has no effect on compilation when dynamic join ordering is not explicitly enabled during compilation.