release-20.1: sql: fix execution of non-scalar count(*) #46891
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It is possible to have non-scalar aggregations with no grouping columns - this happens when the grouping columns are constant and reduced by the optimizer. In this case, we must not produce a row if the input is empty. We plumbed a scalar flag and type through execution, but there is a special fast path for `count(*)` which still relies on just checking if there are no grouping columns. This change fixes this issue and moves this logic into a helper so that the code is not duplicated between the row and col exec. Fixes cockroachdb#45453. Release note (bug fix): fixed incorrect result with count(*) when grouping on constant columns.
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yuzefovich
approved these changes
Apr 1, 2020
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Reviewed 4 of 4 files at r1.
Reviewable status:complete! 0 of 0 LGTMs obtained
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Backport 1/1 commits from #46879.
/cc @cockroachdb/release
It is possible to have non-scalar aggregations with no grouping columns - this
happens when the grouping columns are constant and reduced by the optimizer. In
this case, we must not produce a row if the input is empty. We plumbed a scalar
flag and type through execution, but there is a special fast path for
count(*)which still relies on just checking if there are no grouping columns.
This change fixes this issue and moves this logic into a helper so that the code
is not duplicated between the row and col exec.
Fixes #45453.
Release note (bug fix): fixed incorrect result with count(*) when grouping on
constant columns.