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Posted to issues@hive.apache.org by "Gopal V (JIRA)" <ji...@apache.org> on 2017/09/06 18:59:00 UTC
[jira] [Updated] (HIVE-17465) Statistics: Drill-down filters don't
reduce row-counts progressively
[ https://issues.apache.org/jira/browse/HIVE-17465?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]
Gopal V updated HIVE-17465:
---------------------------
Component/s: Statistics
Physical Optimizer
> 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
>
> {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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