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https://issues.apache.org/jira/browse/IMPALA-8095?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Gabor Kaszab updated IMPALA-8095:
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Fix Version/s: Impala 3.2.0
> Detailed expression cardinality tests
> -------------------------------------
>
> Key: IMPALA-8095
> URL: https://issues.apache.org/jira/browse/IMPALA-8095
> Project: IMPALA
> Issue Type: Improvement
> Components: Frontend
> Affects Versions: Impala 3.1.0
> Reporter: Paul Rogers
> Assignee: Paul Rogers
> Priority: Minor
> Fix For: Impala 3.2.0
>
>
> Cardinality is a critical input to the query planning process, especially
> join planning. Impala has many high-level end-to-end tests that implicitly
> test cardinality at the "wholesale" level: A test will produce a wrong result
> if the cardinality is badly wrong.
> But, at present, no detailed unit tests exist for this topic. This ticket
> asks to add tests for:
> * Table cardinality, NDV values and null count in metadata retrieved from HMS.
> * Table cardinality, NDV values and null counts in metadata presented to the
> query.
> * Expression NDV and selectivity values (which derive from table cardinality
> and column NDV.)
> Since none of the existing "functional" tables provide the level of detail
> needed for these tests, add a new test table specifically for this task.
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