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From Joydeep Sen Sarma <jssa...@facebook.com>
Subject RE: How HIVE manages a join
Date Thu, 12 Aug 2010 07:16:01 GMT
i hate this message: 'THIS PAGE WAS MOVED TO HIVE XDOCS ! DO NOT EDIT!Join Syntax'

why must edits to the wiki be banned if there are xdocs? hadoop has both.

there will always be things that are not captured in xdocs. it's pretty sad to discourage
free form edits by people who want to contribute without checking out source. (what is this
- the 80s?)
________________________________________
From: Edward Capriolo [edlinuxguru@gmail.com]
Sent: Tuesday, August 10, 2010 2:57 PM
To: hive-user@hadoop.apache.org
Cc: hive-dev@hadoop.apache.org
Subject: Re: How HIVE manages a join

Sorry.
$hive_root/docs/xdocs/language_manual/joins.xml

On Tue, Aug 10, 2010 at 5:57 PM, Edward Capriolo <edlinuxguru@gmail.com> wrote:
> This page is is already in version control..
>
> /home/edward/cassandra-handler/docs/xdocs/language_manual/joins.xml
>
> Edward
>
> On Tue, Aug 10, 2010 at 5:15 PM, Carl Steinbach <carl@cloudera.com> wrote:
>> Hi Yongqiang,
>> Please go ahead and update the wiki page. I will copy it over to version
>> control when you are done.
>> Thanks.
>> Carl
>>
>> On Tue, Aug 10, 2010 at 2:11 PM, yongqiang he <heyongqiangict@gmail.com>
>> wrote:
>>>
>>> In the Hive Join wiki page, it says
>>> "THIS PAGE WAS MOVED TO HIVE XDOCS ! DO NOT EDIT!Join Syntax"
>>>
>>> Where should i do the update?
>>>
>>> On Fri, Aug 6, 2010 at 11:46 PM, yongqiang he <heyongqiangict@gmail.com>
>>> wrote:
>>> > Yeah. The sort merge bucket mapjoin has been finished for sometime,
>>> > and seems stable now. I did one skew join but haven't get a chance to
>>> > look at another skew join Namit mentioned to me. But definitely should
>>> > update the wiki earlier. My bad.
>>> >
>>> > On Fri, Aug 6, 2010 at 8:32 PM, Jeff Hammerbacher <hammer@cloudera.com>
>>> > wrote:
>>> >> Yongqiang mentioned he was going to update the wiki with this
>>> >> information in
>>> >> the thread at http://hadoop.markmail.org/thread/hxd4uwwukuo46lgw.
>>> >>
>>> >> Yongqiang, have you gotten a chance to complete the sort merge bucket
>>> >> map
>>> >> join and the other skew join you mention in the above thread?
>>> >>
>>> >> Thanks,
>>> >> Jeff
>>> >>
>>> >> On Fri, Aug 6, 2010 at 3:43 AM, bharath vissapragada
>>> >> <bharat_v@students.iiit.ac.in> wrote:
>>> >>>
>>> >>> Roberto ..
>>> >>>
>>> >>> You can find these links useful ..
>>> >>>
>>> >>>
>>> >>>
>>> >>> http://www.slideshare.net/ragho/hive-icde-2010?src=related_normal&rel=2374551
>>> >>> - Simple joins and optimizations..
>>> >>>
>>> >>>
>>> >>> http://www.slideshare.net/zshao/hive-user-meeting-march-2010-hive-team
 -
>>> >>> New kind of joins / features of hive ..
>>> >>>
>>> >>> Thanks
>>> >>>
>>> >>> Bharath.V
>>> >>> 4th year Undergraduate..
>>> >>> IIIT Hyderabad
>>> >>>
>>> >>> On Fri, Aug 6, 2010 at 12:16 PM, Cappa Roberto
>>> >>> <roberto.cappa@guest.telecomitalia.it> wrote:
>>> >>>>
>>> >>>> Hi,
>>> >>>>
>>> >>>> I cannot find any documentation about what algorithm performs
HIVE to
>>> >>>> translate JOIN clauses to Map-Reduce tasks.
>>> >>>>
>>> >>>> In particular, if I have two tables A and B, each table is written
on
>>> >>>> a
>>> >>>> separate file and each file is splitted on hadoop nodes. When
I
>>> >>>> perform a
>>> >>>> JOIN with A.column = B.column, the framework has to compare
full data
>>> >>>> from
>>> >>>> the first file and full data from the second file. In order
to
>>> >>>> perform a
>>> >>>> full scan of all possibile combinations of values, how can hadoop
>>> >>>> perform
>>> >>>> it? If each node contains a portion of each file, it seems not
>>> >>>> possible to
>>> >>>> have a complete comparison. Does one of the two files enterely
>>> >>>> replicated on
>>> >>>> each node? Or, does HIVE use another kind of strategy/optimization?
>>> >>>>
>>> >>>> Thanks.
>>> >>
>>> >>
>>> >
>>
>>
>

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