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https://issues.apache.org/jira/browse/FLINK-5315?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16559889#comment-16559889
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Rong Rong commented on FLINK-5315:
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Yes [~hequn8128]. Currently I am transferring the distinct modifier for the
parameters towards the aggregate function.
However, I think {{a.count.distinct}} is confusing, since {{a.count}} returns a
valid expression, and {{<expr>.distinct}} is as well a valid expression, but
chaining 2 aggregates together is not a valid expression though. So it is not
immediately clear to end users what this means.
But the point seems to be interesting when considering multiple parameters like
[~fhueske] mentioned: {{multiParamAgg('a.distinct, 'b.distinct)}} seems to
duplicate the unnecessary {{distinct}} twice which can be a burden to user to
specify multiple times. So on the UDAGG side, I think the proposal to use
`udagg.distinct('a, 'b)` seems to be a good idea.
Thoughts?
> Support distinct aggregations in table api
> ------------------------------------------
>
> Key: FLINK-5315
> URL: https://issues.apache.org/jira/browse/FLINK-5315
> Project: Flink
> Issue Type: Sub-task
> Components: Table API & SQL
> Reporter: Kurt Young
> Assignee: Rong Rong
> Priority: Major
>
> Such as
> {code}
> t.select("count(distinct a), sum(b)")
> {code}
> or
> {code}
> t.select('a.count.distinct), 'b.sum)
> {code}
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