[jira] [Commented] (IMPALA-12383) Aggregation with num_nodes=1 and limit returns too many rows

["Michael Smith (Jira)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/IMPALA-12383?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17755731#comment-17755731 ] 

Michael Smith commented on IMPALA-12383:
----------------------------------------

[~sql_forever] [~liuyao] my best take on how to address this is to mark FINALIZE aggregators that we know have a preagg step as having preagg, and only do pushdown on those. If there's no preagg, I don't think pushdown makes sense.

> Aggregation with num_nodes=1 and limit returns too many rows
> ------------------------------------------------------------
>
>                 Key: IMPALA-12383
>                 URL: https://issues.apache.org/jira/browse/IMPALA-12383
>             Project: IMPALA
>          Issue Type: Bug
>          Components: Backend, Frontend
>    Affects Versions: Impala 4.1.0
>            Reporter: Michael Smith
>            Priority: Major
>
> With {{set num_nodes=1}} to select SingleNodePlanner, aggregations return too many rows:
> {code}
> > select distinct l_orderkey from tpch.lineitem limit 10;
> ...
> Fetched 16 row(s) in 0.12s
> > select ss_cdemo_sk from tpcds.store_sales group by ss_cdemo_sk limit 3;
> ...
> Fetched 7 row(s) in 0.14s
> {code}
> This looks like it's caused by changes in IMPALA-2581, which attempts to push down limits to pre-aggregation. In SingleNodePlanner, there is no pre-aggregation, which the patch appears to have failed to account for.



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