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From: Apache Wiki <wikidiffs@apache.org>
To: Apache Wiki <wikidiffs@apache.org>
Date: Fri, 30 Apr 2010 20:57:13 -0000
Message-ID: <20100430205713.19572.38372@eos.apache.org>
Subject: 
 =?utf-8?q?=5BHadoop_Wiki=5D_Update_of_=22Hive/LanguageManual/DDL=22_by_Pa?=
 =?utf-8?q?ulYang?=

Dear Wiki user,

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

The "Hive/LanguageManual/DDL" page has been changed by PaulYang.
http://wiki.apache.org/hadoop/Hive/LanguageManual/DDL?action=3Ddiff&rev1=3D=
58&rev2=3D59

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

  =

  NOTE: These commands will only modify Hive's metadata, and will NOT reorg=
anize or reformat existing data. Users should make sure the actual data lay=
out conforms with the metadata definition.
  =

- =3D=3D=3D Alter Table Touch =3D=3D=3D =

+ =3D=3D=3D Alter Table Touch =3D=3D=3D
  {{{
  ALTER TABLE table_name TOUCH;
  ALTER TABLE table_name TOUCH PARTITION partition_spec;
  }}}
  =

- Touch reads the metadata, and writes it back. This has the effect of caus=
ing the pre/post execute hooks to fire. An example use case might be if you=
 have a hook that logs all the tables/partitions that were modified. Then, =
if you have an external script that alters the files on HDFS directly, the =
modification wouldn't be logged it was performed outside of Hive. The exter=
nal script could call TOUCH to fire the hook and mark the said table or par=
tition as being modified.
+ TOUCH reads the metadata, and writes it back. This has the effect of caus=
ing the pre/post execute hooks to fire. An example use case might be if you=
 have a hook that logs all the tables/partitions that were modified. Then, =
if you have an external script that alters the files on HDFS directly, the =
modification wouldn't be logged it was performed outside of Hive. The exter=
nal script could call TOUCH to fire the hook and mark the said table or par=
tition as being modified.
  =

  Also, it may be useful later if we incorporate reliable last modified tim=
es. Then touch would update that time as well.
  =

- Note that TOUCH doesn't create a table or partition if it doesn't already=
 exist. (See [[Hive/LanguageManual/DDL/Create_Table|Create Table]]
+ Note that TOUCH doesn't create a table or partition if it doesn't already=
 exist. (See [[Hive/LanguageManual/DDL/Create_Table|Create Table]])
  =

  =3D=3D Create/Drop View =3D=3D
 =20