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From "Zoltan Haindrich (Jira)" <j...@apache.org>
Subject [jira] [Commented] (HIVE-22893) Enhance data size estimation for fields computed by UDFs
Date Tue, 25 Feb 2020 08:12:00 GMT

    [ https://issues.apache.org/jira/browse/HIVE-22893?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17044210#comment-17044210
] 

Zoltan Haindrich commented on HIVE-22893:
-----------------------------------------

[~jcamachorodriguez] could you please take a look?

> Enhance data size estimation for fields computed by UDFs
> --------------------------------------------------------
>
>                 Key: HIVE-22893
>                 URL: https://issues.apache.org/jira/browse/HIVE-22893
>             Project: Hive
>          Issue Type: Improvement
>          Components: Statistics
>            Reporter: Zoltan Haindrich
>            Assignee: Zoltan Haindrich
>            Priority: Major
>              Labels: pull-request-available
>         Attachments: HIVE-22893.01.patch, HIVE-22893.02.patch, HIVE-22893.03.patch, HIVE-22893.04.patch,
HIVE-22893.05.patch, HIVE-22893.06.patch, HIVE-22893.07.patch, HIVE-22893.08.patch, HIVE-22893.09.patch,
HIVE-22893.10.patch, HIVE-22893.11.patch, HIVE-22893.12.patch
>
>          Time Spent: 10m
>  Remaining Estimate: 0h
>
> Right now if we have columnstat on a column ; we use that to estimate things about the
column; - however if an UDF is executed on a column ; the resulting column is treated as unknown
thing and defaults are assumed.
> An improvement could be to give wide estimation(s) in case of frequently used udf.
> For example; consider {{substr(c,1,1)}} ; no matter what the input; the output is at
most a 1 long string



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