hadoop-hive-dev mailing list archives

Site index · List index
Message view « Date » · « Thread »
Top « Date » · « Thread »
From "Namit Jain (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HIVE-72) wrong results if partition pruning not strict and no mep-reduce job needed
Date Wed, 19 Nov 2008 00:37:44 GMT

    [ https://issues.apache.org/jira/browse/HIVE-72?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12648838#action_12648838

Namit Jain commented on HIVE-72:

changed prune() to return the two lists: confirmed and unknown separately and let the client
handle it

> wrong results if partition pruning not strict and no mep-reduce job needed
> --------------------------------------------------------------------------
>                 Key: HIVE-72
>                 URL: https://issues.apache.org/jira/browse/HIVE-72
>             Project: Hadoop Hive
>          Issue Type: Bug
>            Reporter: Namit Jain
>            Assignee: Namit Jain
> Suppose T is a partitioned table on ds, where ds is a string column, the following queries:
>  SELECT a.* FROM T a WHERE a.ds=2008-09-08 LIMIT 1;
>  SELECT a.* FROM T a WHERE a.ds=2008-11-10 LIMIT 1;
> return the first row from the first partition.
> This is because of the typecast to double.
> for a.ds=2008-01-01 or anything (a.ds=1),
>  evaluate (Double, Double) is invoked at partition pruning.
> Since '2008-11-01' is not a valid double, it is converted to a null, and therefore the
result of pruning returns null (unknown) - not FALSE.
> All unknowns are also accepted, therefore all partitions are accepted which explains
this behavior.
> filter is not invoked since it is a select * query, so map-reduce job is started.
> We just turn off this optimization if pruning indicates that there can be unknown partitions.

This message is automatically generated by JIRA.
You can reply to this email to add a comment to the issue online.

View raw message