[jira] [Assigned] (IMPALA-8647) The cardinality associated with a SelectNode is 0 even if its child node has a non-zero cardinality

["Tim Armstrong (Jira)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/IMPALA-8647?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Tim Armstrong reassigned IMPALA-8647:
-------------------------------------

    Assignee: Tim Armstrong

> The cardinality associated with a SelectNode is 0 even if its child node has a non-zero cardinality
> ---------------------------------------------------------------------------------------------------
>
>                 Key: IMPALA-8647
>                 URL: https://issues.apache.org/jira/browse/IMPALA-8647
>             Project: IMPALA
>          Issue Type: Bug
>          Components: Frontend
>            Reporter: Fang-Yu Rao
>            Assignee: Tim Armstrong
>            Priority: Minor
>
> Consider the following nested SQL statement.
> {code:java}
> EXPLAIN SELECT *
> FROM functional_parquet.alltypessmall WHERE 1 IN
> (SELECT int_col FROM functional_parquet.alltypestiny LIMIT 1);
> {code}
> It seems that the cardinality of the SelectNode should be 1 instead of 0. Specifically, if we had executed
> {code:java}
> compute stats functional_parquet.alltypestiny{code}
> before issuing this SQL statement at the very beginning, the returned cardinality of this SelectNode would be 1 instead of 0. Not very sure if this is a bug. It looks like the cardinality of a SelectNode depends on whether there is stats information associated with its child node. The cardinality of a SelectNode would still be 0 even if its child node (ExchangeNode in this case) has a non-zero cardinality.



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