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From Apache Wiki <wikidi...@apache.org>
Subject [Hadoop Wiki] Update of "Hive/ViewDev" by JohnSichi
Date Wed, 30 Dec 2009 20:46:47 GMT
Dear Wiki user,

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The "Hive/ViewDev" page has been changed by JohnSichi.
http://wiki.apache.org/hadoop/Hive/ViewDev?action=diff&rev1=5&rev2=6

--------------------------------------------------

  || ''Metadata queries from existing code/tools'' || Existing queries for tables will NOT
include views in results; those that need to will have to be modified to reference base class
instead || Existing queries for tables WILL include views in results; those that are not supposed
to will need to filter them out ||
  || ''Metastore upgrade on deployment'' || Need to test carefully to make sure introducing
inheritance doesn't corrupt existing metastore instances || Nothing special, just adding a
new attribute ||
  
+ '''Update 30-Dec-2009''':  Based on a design review meeting, we're going to go with the
flat model.  Prasad pointed out that in the future, for materialized views, we may need the
view definition to be tracked at the partition level as well, so that when we change the view
definition, we don't have to discard existing materialized partitions if the new view result
can be derived from the old one.  So it may make sense to add the view definition as a new
attribute of StorageDescriptor (since that is already present at both table and partition
level).
+ 
  == Dependency Tracking ==
  
  It's necessary to track dependencies from a view to objects it references in the metastore:
@@ -69, +71 @@

   * other views:  same as tables
   * columns:  this is optional (useful for lineage inspection, but not required for implementing
SQL features)
   * temporary functions:  we should disallow these at view creation unless we also want a
concept of temporary view (or if it's OK for the referencing view to become invalid whenever
the volatile function registry gets cleared)
-  * any other objects? (e.g. udt's coming in as part of [http://issues.apache.org/jira/browse/HIVE-779
HIVE-779])
+  * any other objects? (e.g. udt's coming in as part of http://issues.apache.org/jira/browse/HIVE-779)
  
  (Note that MySQL doesn't actually implement CASCADE/RESTRICT:  it just ignores the keyword
and drops the table unconditionally, leaving the view dangling.)
  

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