Implement CASE flattening optimizations
#34175
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I'll mark it as ready after adding some tests for the new transformations (they already affect some existing tests, but having some dedicated ones is probably better). |
ranma42
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It filters out all elements after a certain predicate it satisfied.
This makes the expression a little simpler and (especially) normalizes the ELSE sub-expression.
maumar
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Jul 12, 2024
roji
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Jul 12, 2024
| @@ -714,13 +718,117 @@ public virtual SqlExpression Case(SqlExpression? operand, IReadOnlyList<CaseWhen | |||
| var typeMappedWhenClauses = new List<CaseWhenClause>(); | |||
| foreach (var caseWhenClause in whenClauses) | |||
| { | |||
| var test = caseWhenClause.Test; | |||
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| if (operand == null && test is CaseExpression { Operand: null, WhenClauses: [var clause] } testExpr) | |||
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| if (operand == null && test is CaseExpression { Operand: null, WhenClauses: [var clause] } testExpr) | |
| if (operand == null && test is CaseExpression { Operand: null, WhenClauses: [var nestedSingleClause] } testExpr) |
| => expr is SqlConstantExpression { Value: false or null }; | ||
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| bool IsTrue(SqlExpression expr) | ||
| => expr is SqlConstantExpression { Value: true }; |
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Honestly, with pattern matching, the syntax is simple enough that maybe we should just inline, rather than have a helper method like this…
maumar
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Jul 12, 2024
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nice improvement, thanks! |
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It is possible to perform most of the
CASEoptimizations at construction time.This improves the SQL emitted by SqlServer and makes it easy to implement the optimizations proposed in #18774.
Fixes #18774.
Fixes #18935.