Julian Hyde created CALCITE-4763:
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Summary: EXISTS_AGG, an aggregate function that returns whether
count is positive
Key: CALCITE-4763
URL: https://issues.apache.org/jira/browse/CALCITE-4763
Project: Calcite
Issue Type: Bug
Reporter: Julian Hyde
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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