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Fix to #12657 - Query: logic protecting SUM from returning null doesn't work for complex scenarios #21203

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merged 1 commit into from
Jun 15, 2020

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maumar
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@maumar maumar commented Jun 10, 2020

Adding COALESCE around SUM sql function expression

Fixes #12657

@maumar maumar requested review from smitpatel and roji June 10, 2020 06:19
@@ -918,8 +918,13 @@ SqlExpression AddNullConcatenationProtection(SqlExpression argument, RelationalT
arguments[i] = Visit(sqlFunctionExpression.Arguments[i], out _);
}


return sqlFunctionExpression.Update(instance, arguments);
return sqlFunctionExpression.IsBuiltIn
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I'm on the fence here - we do provide Sum translation into SqlFunction "SUM" in relational, but if there is a provider that translates it to a different function it would have to rewrite the entire visit sql function method, so that SUM doesn't get coalesce wrapped around it incorrectly. thoughts? @roji @smitpatel

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For best solution it would be good to put at translation of sum but there is going to be some refactoring coming in when implementing more group by operation and #20633 may be needed for it.

I think this is ok compromise for now, it may not be the best solution but avoids wrong results for customers.

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Of a provider translates to different function, wouldn't they just be responsible for applying the same coalscing in their own nullability processor?

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yeah, its just harder than it needs to be (do the translation + call base vs rewrite entire visit sql function method) but maybe its fine

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maumar commented Jun 10, 2020

updated

…'t work for complex scenarios

Adding COALESCE around SUM sql function expression

Fixes #12657
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Query: logic protecting SUM from returning null doesn't work for complex scenarios
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