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Date: Wed, 13 Sep 2017 22:11:00 +0000 (UTC)
From: "Vineet Garg (JIRA)" <jira@apache.org>
To: issues@hive.apache.org
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Subject: [jira] [Updated] (HIVE-17465) Statistics: Drill-down filters don't
 reduce row-counts progressively
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archived-at: Wed, 13 Sep 2017 22:11:06 -0000


     [ https://issues.apache.org/jira/browse/HIVE-17465?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Vineet Garg updated HIVE-17465:
-------------------------------
    Status: Patch Available  (was: Open)

> Statistics: Drill-down filters don't reduce row-counts progressively
> --------------------------------------------------------------------
>
>                 Key: HIVE-17465
>                 URL: https://issues.apache.org/jira/browse/HIVE-17465
>             Project: Hive
>          Issue Type: Bug
>          Components: Physical Optimizer, Statistics
>            Reporter: Gopal V
>            Assignee: Vineet Garg
>         Attachments: HIVE-17465.1.patch, HIVE-17465.2.patch, HIVE-17465.3.patch, HIVE-17465.4.patch
>
>
> {code}
> explain select count(d_date_sk) from date_dim where d_year=2001 ;
> explain select count(d_date_sk) from date_dim where d_year=2001  and d_moy = 9;
> explain select count(d_date_sk) from date_dim where d_year=2001 and d_moy = 9 and d_dom = 21;
> {code}
> All 3 queries end up with the same row-count estimates after the filter.
> {code}
>             Map Operator Tree:
>                 TableScan
>                   alias: date_dim
>                   filterExpr: (d_year = 2001) (type: boolean)
>                   Statistics: Num rows: 73049 Data size: 82034027 Basic stats: COMPLETE Column stats: COMPLETE
>                   Filter Operator
>                     predicate: (d_year = 2001) (type: boolean)
>                     Statistics: Num rows: 363 Data size: 4356 Basic stats: COMPLETE Column stats: COMPLETE
>  
>         Map 1 
>             Map Operator Tree:
>                 TableScan
>                   alias: date_dim
>                   filterExpr: ((d_year = 2001) and (d_moy = 9)) (type: boolean)
>                   Statistics: Num rows: 73049 Data size: 82034027 Basic stats: COMPLETE Column stats: COMPLETE
>                   Filter Operator
>                     predicate: ((d_year = 2001) and (d_moy = 9)) (type: boolean)
>                     Statistics: Num rows: 363 Data size: 5808 Basic stats: COMPLETE Column stats: COMPLETE
>         Map 1 
>             Map Operator Tree:
>                 TableScan
>                   alias: date_dim
>                   filterExpr: ((d_year = 2001) and (d_moy = 9) and (d_dom = 21)) (type: boolean)
>                   Statistics: Num rows: 73049 Data size: 82034027 Basic stats: COMPLETE Column stats: COMPLETE
>                   Filter Operator
>                     predicate: ((d_year = 2001) and (d_moy = 9) and (d_dom = 21)) (type: boolean)
>                     Statistics: Num rows: 363 Data size: 7260 Basic stats: COMPLETE Column stats: COMPLETE
> {code}


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