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From "Chao Sun (JIRA)" <j...@apache.org>
Subject [jira] [Updated] (HIVE-5921) Better heuristics for worst case statistics estimates for join, limit and filter operator
Date Tue, 13 Dec 2016 21:14:59 GMT

     [ https://issues.apache.org/jira/browse/HIVE-5921?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Chao Sun updated HIVE-5921:
---------------------------
    Assignee: Prasanth Jayachandran  (was: Chao Sun)

> Better heuristics for worst case statistics estimates for join, limit and filter operator
> -----------------------------------------------------------------------------------------
>
>                 Key: HIVE-5921
>                 URL: https://issues.apache.org/jira/browse/HIVE-5921
>             Project: Hive
>          Issue Type: Sub-task
>          Components: Query Processor, Statistics
>    Affects Versions: 0.13.0
>            Reporter: Prasanth Jayachandran
>            Assignee: Prasanth Jayachandran
>             Fix For: 0.13.0
>
>         Attachments: HIVE-5921.1.patch, HIVE-5921.2.patch, HIVE-5921.3.patch, HIVE-5921.4.patch
>
>
> This is a subtask of HIVE-5369. In worst case (i.e; absence of column statistics) HIVE-5849
improved the basic statistics with heuristics. But the heuristics failed to provide better
estimates in few cases. For example: FILTER operator heuristics did not take into account
the number of predicates and if the predicate contains partition column. Also, JOIN estimates
were too aggressive and was not user configurable.



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