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From "Ashutosh Chauhan (JIRA)" <>
Subject [jira] [Commented] (HIVE-14018) Make IN clause row selectivity estimation customizable
Date Wed, 15 Jun 2016 17:59:09 GMT


Ashutosh Chauhan commented on HIVE-14018:


> Make IN clause row selectivity estimation customizable
> ------------------------------------------------------
>                 Key: HIVE-14018
>                 URL:
>             Project: Hive
>          Issue Type: Improvement
>          Components: Statistics
>    Affects Versions: 2.1.0, 2.2.0
>            Reporter: Jesus Camacho Rodriguez
>            Assignee: Jesus Camacho Rodriguez
>            Priority: Minor
>         Attachments: HIVE-14018.patch
> After HIVE-13287 went in, we calculate IN clause estimates natively (instead of just
dividing incoming number of rows by 2). However, as the distribution of values of the columns
is considered uniform, we might end up heavily underestimating/overestimating the resulting
number of rows.
> This issue is to add a factor that multiplies the IN clause estimation so we can alleviate
this problem. The solution is not very elegant, but it is the best we can do until we have
histograms to improve our estimate.

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