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https://issues.apache.org/jira/browse/CALCITE-3128?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16874480#comment-16874480
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Julian Hyde commented on CALCITE-3128:
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Does this problem occur if and only if the condition is always true? I think
not.
if the condition is '(t1.c is null) = (t2.c is null)', I think the problem
would still occur. The key factor, I think, is that one side has just one
column, and a null in that column.
So I don't think {{boolean isConditionAlwaysTrue}} should be part of the
solution.
> Joining two tables producing only NULLs will return 0 rows
> ----------------------------------------------------------
>
> Key: CALCITE-3128
> URL: https://issues.apache.org/jira/browse/CALCITE-3128
> Project: Calcite
> Issue Type: Bug
> Components: core
> Affects Versions: 1.20.0
> Reporter: Muhammad Gelbana
> Assignee: Danny Chan
> Priority: Major
> Labels: pull-request-available
> Time Spent: 2h 10m
> Remaining Estimate: 0h
>
> The following queries will return 0 rows while they're expected to ruturn
> rows with NULLs in them.
> {code:sql}
> SELECT *
> FROM (SELECT NULLIF(5, 5)) a, (SELECT NULLIF(5, 5)) b
> {code}
> {code:sql}
> SELECT *
> FROM (VALUES (NULLIF(5, 5)), (NULLIF(5, 5))) a, (VALUES (NULLIF(5, 5)),
> (NULLIF(5, 5))) b
> {code}
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