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