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https://issues.apache.org/jira/browse/CALCITE-993?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15042284#comment-15042284
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Julian Hyde commented on CALCITE-993:
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I just realized there's a problem. Suppose that the expression is constant but
evaluates to null. For example,
{code}SELECT NULLIF(1, 1) AS c FROM t{code}
It is not valid to infer the predicate {{c = NULLIF(1, 1)}}. Only {{c IS NOT
DISTINCT FROM NULLIF(1, 1)}} is valid. But I bet that we can't use predicates
based on {{IS NOT DISTINCT FROM}} as widely as we can use {{=}}.
> Predicate Pull up above Project enhancement
> -------------------------------------------
>
> Key: CALCITE-993
> URL: https://issues.apache.org/jira/browse/CALCITE-993
> Project: Calcite
> Issue Type: Bug
> Components: core
> Affects Versions: 1.5.0
> Reporter: Laljo John Pullokkaran
> Assignee: Laljo John Pullokkaran
>
> Predicate Pull up on Project can also pull up deterministic functions whose
> arguments are all literals.
> Ex: select r1.x from (select cast('10' as int) as x, y from r1 where y<10)r1
> join r2 on r1.x=r2.x;
> Currently deterministic functions involving constants are ignored which
> results in missed transitive inference.
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