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From Apache Wiki <wikidi...@apache.org>
Subject [Hadoop Wiki] Update of "Hive/Locking" by NamitJain
Date Wed, 05 May 2010 01:19:01 GMT
Dear Wiki user,

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The "Hive/Locking" page has been changed by NamitJain.
http://wiki.apache.org/hadoop/Hive/Locking?action=diff&rev1=4&rev2=5

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

  Concurrency support (http://issues.apache.org/jira/browse/HIVE-1293) is a must in databases
and their usecases are well understood. At a minimum, we want to support concurrent readers
and writers whenever possible.
  It would be useful to add a mechanism to discover the current locks which have been acquired.
There is no immediate requirement to add an API to explicitly acquire any locks, so all locks
would be acquired implicitly.
  
- he following lock modes are defined in hive (Note that Intent lock is not needed).
+ The following lock modes are defined in hive (Note that Intent lock is not needed).
  
- Shared    (S)
+  * Shared    (S)
- Exclusive (X)
+  * Exclusive (X)
  
- As the name suggests, multiple shared locks can be acquired at the same time, whereas X
lock blocks all
+ As the name suggests, multiple shared locks can be acquired at the same time, whereas X
lock blocks all other locks.
- other locks.
  
  The compatiblity matrix is as follows:
  

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