Fix optimization of CASE op WHEN
#33869
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ranma42
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The new translation avoids duplicating sub-expressions and introducing negations.
ranma42
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ranma42
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Jun 3, 2024
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| return _sqlExpressionFactory.Case( | ||
| instance, | ||
| new[] | ||
| { | ||
| new CaseWhenClause( | ||
| _sqlExpressionFactory.Equal(instance, _sqlExpressionFactory.Constant(false)), | ||
| _sqlExpressionFactory.Constant(false), | ||
| _sqlExpressionFactory.Constant(false.ToString())), | ||
| new CaseWhenClause( | ||
| _sqlExpressionFactory.Equal(instance, _sqlExpressionFactory.Constant(true)), | ||
| _sqlExpressionFactory.Constant(true), | ||
| _sqlExpressionFactory.Constant(true.ToString())) |
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this is the same approach recommended by @roji in #33706 (comment) 🚀
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Will let @maumar review/approve but this looks great... I remember this form of CASE/WHEN (with an operand) was introduced a bit later back in the day, I don't think we were aware of it originally; so I'm not surprised we have the less efficient other variant in various places - may be worth doing a pass over the code base for those.
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I will do the full sweep of our code, but that can be done independently of this PR
maumar
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Jun 3, 2024
|
Thanks @ranma42 - great stuff as always! |
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The
CASE op WHEN ...expression was incorrectly optimized as if it were aCASE WHENexpression if the test expressions contained aTRUEvalue.This also makes it possible to use the
CASE op WHENexpression to avoid duplicating some subexpressions in the translation of the bool to string conversion.Fixes #33867.