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From "Jesus Camacho Rodriguez (JIRA)" <j...@apache.org>
Subject [jira] [Updated] (HIVE-14265) Partial stats in Join operator may lead to data size estimate of 0
Date Mon, 18 Jul 2016 12:33:20 GMT

     [ https://issues.apache.org/jira/browse/HIVE-14265?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Jesus Camacho Rodriguez updated HIVE-14265:
-------------------------------------------
    Status: Patch Available  (was: In Progress)

> Partial stats in Join operator may lead to data size estimate of 0
> ------------------------------------------------------------------
>
>                 Key: HIVE-14265
>                 URL: https://issues.apache.org/jira/browse/HIVE-14265
>             Project: Hive
>          Issue Type: Bug
>          Components: Statistics
>            Reporter: Nita Dembla
>            Assignee: Jesus Camacho Rodriguez
>         Attachments: HIVE-14265.patch
>
>
> For some tables, we might not have the column stats available. However, if the table
is partitioned, we will have the stats for partition columns.
> When we estimate the size of the data produced by a join operator, we end up using only
the columns that are available for the calculation e.g. partition columns in this case.
> However, even in these cases, we should add the data size for those columns for which
we do not have stats (_default size for the column type x estimated number of rows_).
> To reproduce, the following example can be used:
> {noformat}
> create table sample_partitioned (x int) partitioned by (y int);
> insert into sample_partitioned partition(y=1) values (1),(2);
> create temporary table sample as select * from sample_partitioned;
> analyze table sample compute statistics for columns;
> explain select sample_partitioned.x from sample_partitioned, sample where sample.y =
sample_partitioned.y;
> {noformat}



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