[jira] [Updated] (HIVE-16757) Use memoization in HiveRelMdRowCount.getRowCount

["Remus Rusanu (JIRA)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/HIVE-16757?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Remus Rusanu updated HIVE-16757:
--------------------------------
    Attachment: HIVE-16757.01.patch

Patch 01 for running the tests 

> Use memoization in HiveRelMdRowCount.getRowCount
> ------------------------------------------------
>
>                 Key: HIVE-16757
>                 URL: https://issues.apache.org/jira/browse/HIVE-16757
>             Project: Hive
>          Issue Type: Bug
>          Components: Query Planning
>            Reporter: Remus Rusanu
>            Assignee: Remus Rusanu
>         Attachments: HIVE-16757.01.patch
>
>
> On complex queries HiveRelMdRowCount.getRowCount can get called many times. since it does not memoize its result and the call is recursive, it results in an explosion of calls. for example a query with 49 joins, during join ordering (LoptOtimizerJoinRule) the HiveRelMdRowCount.getRowCount gets called 6442 as a top level call, but the recursivity exploded this to 501729 calls. Memoization of the rezult would stop the recursion early. In my testing this reduced the join reordering time for said query from 11s to <1s..



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