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https://issues.apache.org/jira/browse/CALCITE-4763?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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duan xiong updated CALCITE-4763:
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Summary: add EXISTS_AGG aggregate function (was: EXISTS_AGG, an aggregate
function that returns whether count is positive)
> add EXISTS_AGG aggregate function
> ---------------------------------
>
> Key: CALCITE-4763
> URL: https://issues.apache.org/jira/browse/CALCITE-4763
> Project: Calcite
> Issue Type: Bug
> Reporter: Julian Hyde
> Assignee: duan xiong
> Priority: Major
>
> Add {{EXISTS_AGG}}, an aggregate function that returns whether count is
> greater than zero.
> Thus {{EXISTS_AGG(*)}} is equivalent to {{COUNT(*) > 0}}, and
> {{EXISTS_AGG(c)}} is equivalent to {{COUNT(c) > 0}}.
> {{EXISTS_AGG}} would mainly be of use internally. Since it produces a
> {{BOOLEAN}} value, we can use the value directly from an {{Aggregate}}
> without an intervening {{Project}}. It also captures the fact that we don't
> care how many rows were produced.
> See also {{TRUE_AGG}}, CALCITE-4334.
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