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fix: follow a text set operation through a scalar subquery in the guard's rewrite (#505) - #508
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…rd's rewrite (#505) The guard's walker treats a scalar subquery that projects a text Union, Add, Intersect or Except as derived, and so lets ==, != and Count over it through, trusting the expander to write them as mutual containment and count(DISTINCT). The expander's IsDerived had no arm for a scalar subquery, so the raw = and cardinality reached the server and compared the unsorted array_cat: {a,c} ∪ {a,b} == {a,b,c} dropped the row, and (… ?? subquery).Count counted {a,c,a,b} as 4. 10.3.0 refused the query. IsDerived now judges a scalar subquery by its one projection, as the walker does. UnionCanonicalityTests runs ==, != and Count over COALESCE through a correlated scalar subquery, and Add, Intersect and Except the same way, against memory over the loaded rows; with the arm removed both new tests fail on the answer. Found-By: RV Defect-Class: SQL Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
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This was referenced Oct 26, 2026
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Closes #505
Problem
ValueSetSqlGuarddecides in two places whether a value may be an unsorted text set, and the two disagreed on a scalar subquery.Union,Add,IntersectorExceptas derived. So it lets==,!=andCountover it through, because the expander writes those as mutual containment andcount(DISTINCT …)(Translate text value set Intersect, Except, Add, Count and equality where the result needs no order (StringSet, StringSet<T>) #485).IsDerivedhad no arm for a scalar subquery, so the raw=,<>andcardinalityreached the server and compared the unsortedarray_cat.On
{a,c},….Select(o => o.Tags.Union({a,b})).FirstOrDefault() == {a,b,c}dropped the row.(r.OptionalTags ?? subquery).Countcounted{a,c,a,b}as 4. 10.3.0 threw for the same query, so on 10.x this is a regression in the unreleased 10.4.0. It shipped in no release.Change
CanonicalExpander.IsDerivedjudges a scalar subquery by its one projection, as the walker does (ValueSetSqlGuard.cs).guard-rewrite-misses-a-scalar-subquery, caught byUnionCanonicalityTests.No changelog row: the wrong answer shipped in no release. On
main, #485's text forms are in 11.0.0-preview.1's Added, which this makes true.Tests
UnionCanonicalityTests(integration) gains two tests, each comparing the server's answer with LINQ over the loaded rows:EqualityOnAUnionFromAScalarSubquery_AnswersAsMemoryDoes:==,!=and==behind aCOALESCE, through a correlated scalar subquery, andAdd,IntersectandExceptthe same way.CountOverAUnionFromAScalarSubquery_CountsTheDistinctElements_AsMemoryDoes:Countbehind aCOALESCE.dotnet run tools/oracles.cs seeds guard-rewritereports the seed caught (2 of 17 tests fail).🤖 Generated with Claude Code