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From "Aman Sinha (JIRA)" <j...@apache.org>
Subject [jira] [Updated] (DRILL-2327) Upper bound on join's row_count_estimate_factor should be increased to handle expanding joins
Date Fri, 27 Feb 2015 16:53:04 GMT

     [ https://issues.apache.org/jira/browse/DRILL-2327?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Aman Sinha updated DRILL-2327:
------------------------------
    Attachment: 0001-DRILL-2327-Raise-the-max-value-allowed-for-join-s-ca.patch

The row_count_estimate_factor parameter is of type double and I raised the upper bound to
Double.MAX_VALUE.  Note that even if the NDV statistics for join columns were available, there
are certain joins (particularly expanding joins and joins where columns are correlated to
one another) where getting good estimates is difficult.  Hence, having a knob to control the
estimated cardinality is useful for the optimizer. 

[~jni] could you pls take a look at the minor change. 

> Upper bound on join's row_count_estimate_factor should be increased to handle expanding
joins
> ---------------------------------------------------------------------------------------------
>
>                 Key: DRILL-2327
>                 URL: https://issues.apache.org/jira/browse/DRILL-2327
>             Project: Apache Drill
>          Issue Type: Improvement
>          Components: Query Planning & Optimization
>            Reporter: Aman Sinha
>            Assignee: Aman Sinha
>             Fix For: 0.8.0
>
>         Attachments: 0001-DRILL-2327-Raise-the-max-value-allowed-for-join-s-ca.patch
>
>
> The current bounds for planner.join.row_count_estimate_factor is between 0 to 100.  The
default value is 1.0.  This parameter determines the estimated output cardinality of a join.
 For hugely expanding joins, this is inadequate and we need to allow substantially larger
upper bound. 



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