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https://issues.apache.org/jira/browse/IMPALA-8021?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Paul Rogers resolved IMPALA-8021.
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Resolution: Fixed
> Add estimated cardinality to EXPLAIN output
> -------------------------------------------
>
> Key: IMPALA-8021
> URL: https://issues.apache.org/jira/browse/IMPALA-8021
> Project: IMPALA
> Issue Type: Improvement
> Components: Frontend
> Affects Versions: Impala 3.1.0
> Reporter: Paul Rogers
> Assignee: Paul Rogers
> Priority: Minor
>
> The EXPLAIN output provides much useful information in the plan tree. All our
> planning decisions are based on cardinality; but it appears in the EXPLAIN
> output only for the EXTENDED level. The profile only contains the plan from
> the STANDARD level. This change proposes to include row size and cardinality
> even in the STANDARD level.
> The nodes that have the information call it "cardinality", so continue to use
> that term.
> Add cardinality to each node so it appears something like this:
> {noformat}
> HASH JOIN [INNER JOIN, BROADCAST]
> | row-size=89B cardinality=1.23G
> |
> |--SCAN HDFS [db.table]
> | partitions=2/123 files=2 size=4.56MB row-size=89B cardinality=7.89M
> {noformat}
> Cardinality should appear in all levels above MINIMAL. Cardinality is not
> needed for EXCHANGE since it can be inferred from other nodes.
> Also, the existing code prints large cardinalities in detail: 1234567890,
> which is hard to read. Use the abbreviated output, using metric (power of
> 1000) units, so 1.23G instead.
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