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From "John Sichi (JIRA)" <j...@apache.org>
Subject [jira] Created: (HIVE-1067) CREATE VIEW followup: impose casts on view result columns if underlying column types change
Date Wed, 20 Jan 2010 21:41:54 GMT
CREATE VIEW followup:  impose casts on view result columns if underlying column types change
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                 Key: HIVE-1067
                 URL: https://issues.apache.org/jira/browse/HIVE-1067
             Project: Hadoop Hive
          Issue Type: Improvement
          Components: Query Processor
    Affects Versions: 0.6.0
            Reporter: John Sichi
            Assignee: John Sichi
             Fix For: 0.6.0


Consider

CREATE TABLE t(i INT);
CREATE VIEW v AS SELECT i FROM t;
ALTER TABLE t REPLACE COLUMNS (i STRING);
SELECT i FROM v;

What will be the result type for i in the final SELECT?

Consensus at code review was that it should be INT (not STRING) since the CREATE VIEW is supposed
to freeze the metadata for the view's result schema.  Note that SQL:2008 ALTER COLUMN SET
DATA TYPE doesn't cover this case, because it doesn't support changing the datatype family.
 For this case, MySQL produces VARCHAR rather than INT, and (consistently) DESCRIBE v and
INFORMATION_SCHEMA show VARCHAR as well, so either they are propagating the type change in
the catalog, or dynamically re-deriving it.


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