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From "John Sichi (JIRA)" <j...@apache.org>
Subject [jira] Created: (HIVE-1392) minimize execution for (sub)queries which are guaranteed to return no results
Date Fri, 04 Jun 2010 18:50:54 GMT
minimize execution for (sub)queries which are guaranteed to return no results
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                 Key: HIVE-1392
                 URL: https://issues.apache.org/jira/browse/HIVE-1392
             Project: Hadoop Hive
          Issue Type: Improvement
          Components: Query Processor
    Affects Versions: 0.5.0
            Reporter: John Sichi
             Fix For: 0.6.0


Examples would be a predicate like

WHERE 1=0

or

WHERE ds='2010-01-01'

if the table is partitioned on ds and no partition exists for that date.

Per HIVE-838, we have to be careful with the relational algebra analysis; operators like union,
outer join, and full-table aggregation can cause rows to be produced even when one of the
inputs is guaranteed to be completely filtered out.


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