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From "Phabricator (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HIVE-3509) Exclusive locks are not acquired when using dynamic partitions
Date Fri, 19 Apr 2013 16:23:16 GMT

    [ https://issues.apache.org/jira/browse/HIVE-3509?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13636551#comment-13636551
] 

Phabricator commented on HIVE-3509:
-----------------------------------

MattMartin has commented on the revision "HIVE-3509 [jira] Exclusive locks are not acquired
when using dynamic partitions".

  For the record, I'm planning to roll back the "major change" in my last revision which acquires
and releases the whole hierarchy of locks on explicit "lock ..." and "unlock ...".

INLINE COMMENTS
  ql/src/java/org/apache/hadoop/hive/ql/lockmgr/HiveLockObject.java:144 This change should
only affect locks.  In particular, this would make sure the lock paths are consistent for
dummy partitions and non-dummy partitions.

  Without this change, I think a case could arise where a write query with dynamic partitions
tries to acquire an exclusive lock on "<base dir in zookeeper>/db@table@partns" while
a read query simultaneously tries to acquire a shared lock on "<base locking dir in zookeeper>/db/table/partns".
In this case the reader and writer would not block each other even though they should. I'll
try to add a test case to illustrate this point.

REVISION DETAIL
  https://reviews.facebook.net/D10065

To: JIRA, MattMartin
Cc: njain

                
> Exclusive locks are not acquired when using dynamic partitions
> --------------------------------------------------------------
>
>                 Key: HIVE-3509
>                 URL: https://issues.apache.org/jira/browse/HIVE-3509
>             Project: Hive
>          Issue Type: Bug
>          Components: Locking
>    Affects Versions: 0.9.0
>            Reporter: Matt Martin
>            Assignee: Matt Martin
>         Attachments: HIVE-3509.1.patch.txt, HIVE-3509.D10065.1.patch, HIVE-3509.D10065.2.patch,
HIVE-3509.D10065.3.patch, HIVE-3509.D10065.4.patch
>
>
> If locking is enabled, the acquireReadWriteLocks() method in org.apache.hadoop.hive.ql.Driver
iterates through all of the input and output entities of the query plan and attempts to acquire
the appropriate locks.  In general, it should acquire SHARED locks for all of the input entities
and exclusive locks for all of the output entities (see the Hive wiki page on [locking|https://cwiki.apache.org/confluence/display/Hive/Locking]
for more detailed information).
> When the query involves dynamic partitions, the situation is a little more subtle.  As
the Hive wiki notes (see previous link):
> {quote}
> in some cases, the list of objects may not be known - for eg. in case of dynamic partitions,
the list of partitions being modified is not known at compile time - so, the list is generated
conservatively. Since the number of partitions may not be known, an exclusive lock is taken
on the table, or the prefix that is known.
> {quote}
> After [HIVE-1781|https://issues.apache.org/jira/browse/HIVE-1781], the observed behavior
is no longer consistent with the behavior described above.  [HIVE-1781|https://issues.apache.org/jira/browse/HIVE-1781]
appears to have altered the logic so that SHARED locks are acquired instead of EXCLUSIVE locks
whenever the query involves dynamic partitions.

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