[jira] [Resolved] (IMPALA-8022) Add cardinality checks to PlannerTest

["Paul Rogers (JIRA)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/IMPALA-8022?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Paul Rogers resolved IMPALA-8022.
---------------------------------
    Resolution: Fixed

> Add cardinality checks to PlannerTest
> -------------------------------------
>
>                 Key: IMPALA-8022
>                 URL: https://issues.apache.org/jira/browse/IMPALA-8022
>             Project: IMPALA
>          Issue Type: Improvement
>          Components: Frontend
>    Affects Versions: Impala 3.1.0
>            Reporter: Paul Rogers
>            Assignee: Paul Rogers
>            Priority: Minor
>
> IMPALA-8021 suggests that we add cardinality to the standard EXPLAIN output. When we do so, the cardinality will appear in the plans generated by {{PlannerTest}}. We could just ignore the numbers, as we do for other derived values. Or, we could use this opportunity to verify the expected cardinalities.
> The expected cardinality is a critical number when planning queries: we decide join planning based on that number (sometimes multiplied by row width.) To prevent regressions, we want to verify that we've not changed the cardinality estimates except by design.
> Since cardinality estimates may vary a bit, do a range-based comparison, accepting as valid any value within 5% of the expected value. (Except for zero, if zero is expected, the actual estimate must also be zero.)



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