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https://issues.apache.org/jira/browse/CALCITE-7722?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=18106060#comment-18106060
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Mihai Budiu commented on CALCITE-7722:
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I am wondering whether Calcite isn't too strict about exceptions.
Here is a quote from the SQL standard from 92:
{color:#FF0000}If the result of an expression or search condition can be
determined without completely evaluating all parts of the expression or search
condition, then the parts of the expression or search condition whose
evaluation is not necessary are called the inessential parts. [...] If
evaluation of the inessential parts would cause an exception condition to be
raised, then it is implementation-dependent whether or not that exception
condition is raised.{color}
So perhaps we are too keen to preserve exceptions?
> RexSimplify IS [NOT] NULL on a safe operator with Strong policy ANY and
> unsafe operands can be further simplified
> -----------------------------------------------------------------------------------------------------------------
>
> Key: CALCITE-7722
> URL: https://issues.apache.org/jira/browse/CALCITE-7722
> Project: Calcite
> Issue Type: Improvement
> Reporter: Thomas Rebele
> Assignee: Ruben Q L
> Priority: Major
> Labels: pull-request-available
> Fix For: 1.43.0
>
>
> RexSimplify.simplifyIsNotNull / simplifyIsNull currently bail out of the
> whole simplification when the input RexCall is not fully safe (i.e.
> isSafeExpression(a) == false). This is stricter than necessary for operators
> with Strong.Policy.ANY, where IS [NOT] NULL(f(a, b, ...)) is semantically
> equivalent to IS [NOT] NULL(a) OR/AND IS [NOT] NULL(b) OR/AND ... — the
> operator itself does not need to be evaluated to compute the result.
> Example (regression for downstream projects such as Hive):
> {code}
> Before (≤ 1.34):
> IS NOT NULL(CAST(myStr AS DOUBLE) + 1.0) → IS NOT NULL(CAST(myStr AS DOUBLE))
> After (≥ 1.35):
> IS NOT NULL(CAST(myStr AS DOUBLE) + 1.0) → (unchanged)
> {code}
> The rewrite is dropped because CAST(key AS DOUBLE) + 1.0 is a non-lossless
> cast wrapped in a +, so isSafeExpression returns false, even though + is
> Strong.ANY and the distribution is a valid rewrite regardless of the outer
> call's safety.
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