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From: Apache Wiki <wikidiffs@apache.org>
To: Apache Wiki <wikidiffs@apache.org>
Date: Wed, 02 Feb 2011 01:25:33 -0000
Message-ID: <20110202012533.47643.42301@eosnew.apache.org>
Subject: 
 =?utf-8?q?=5BHadoop_Wiki=5D_Update_of_=22Hive/PartitionedViews=22_by_John?=
 =?utf-8?q?Sichi?=

Dear Wiki user,

You have subscribed to a wiki page or wiki category on "Hadoop Wiki" for ch=
ange notification.

The "Hive/PartitionedViews" page has been changed by JohnSichi.
http://wiki.apache.org/hadoop/Hive/PartitionedViews?action=3Ddiff&rev1=3D8&=
rev2=3D9

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

  =3D Approaches =3D
  =

   1. One possible approach mentioned in [[https://issues.apache.org/jira/b=
rowse/HIVE-1079|HIVE-1079]] is to infer view partitions automatically based=
 on the partitions of the underlying tables.  A command such as SHOW PARTIT=
IONS could then synthesize virtual partition descriptors on the fly.  This =
is fairly easy to do for use case #1, but potentially very difficult for us=
e cases #2 and #3.  So for now, we are punting on this approach.
-  1. Instead, per [[https://issues.apache.org/jira/browse/HIVE-1941|HIVE-1=
941]], we will require users to explicitly declare view partitioning as par=
t of CREATE VIEW, and explicitly manage partition metadata via ALTER VIEW {=
ADD|DROP} PARTITION.  This allows all of the use cases to be satisfied (whi=
le placing more burden on the user, and taking up more metastore space).  W=
ith this approach, there is no real connection between view partitions and =
underlying table partitions; it's even possible to create a partitioned vie=
w on an unpartitioned table, or to have data in the view which is not cover=
ed by any view partition.  One downside here is that a UI will not be able =
to show physical information such as file size when browsing available part=
itions.
+  1. Instead, per [[https://issues.apache.org/jira/browse/HIVE-1941|HIVE-1=
941]], we will require users to explicitly declare view partitioning as par=
t of CREATE VIEW, and explicitly manage partition metadata via ALTER VIEW {=
ADD|DROP} PARTITION.  This allows all of the use cases to be satisfied (whi=
le placing more burden on the user, and taking up more metastore space).  W=
ith this approach, there is no real connection between view partitions and =
underlying table partitions; it's even possible to create a partitioned vie=
w on an unpartitioned table, or to have data in the view which is not cover=
ed by any view partition.  One downside here is that a UI will not be able =
to show last access time and physical information such as file size when br=
owsing available partitions.  (And stats won't work without an explicit ANA=
LYZE.)
  =

  =3D Syntax =3D
 =20