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From "Adam Kramer (JIRA)" <j...@apache.org>
Subject [jira] Created: (HIVE-1490) More implicit type conversion: UNION ALL and COALESCE
Date Tue, 27 Jul 2010 20:36:16 GMT
More implicit type conversion: UNION ALL and COALESCE
-----------------------------------------------------

                 Key: HIVE-1490
                 URL: https://issues.apache.org/jira/browse/HIVE-1490
             Project: Hadoop Hive
          Issue Type: Improvement
          Components: Query Processor, Server Infrastructure
            Reporter: Adam Kramer


This is a usecase that frequently annoys me:

SELECT TRANSFORM(stuff)
USING 'script'
AS thing1, thing2
FROM some_table

UNION ALL

SELECT a.thing1, a.thing2
FROM some_other_table a

...this fails when a.thing1 and a.thing2 are anything but STRING, because all output of TRANSFORM
is STRING.

In this case, a.thing1 and a.thing2 should be implicitly converted to string.

COALESCE(a.thing1, a.thing2, a.thing3) should similarly do implicit type conversion among
the arguments. If two are INT and one is BIGINT, upgrade the INTs, etc.

At the very least, it would be nice to have syntax like

SELECT TRANSFORM(stuff)
USING 'script'
AS thing1 INT, thing2 INT

...which would effectively cast the output column to the specified type. But really, type
conversion should work.

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