Grokbase Groups Pig user October 2010
FAQ
As long as the loader can provide statistics (be it Howl loader, or
something else), we can use stats to make optimizations. There is actually a
(very simplistic) example of this already in 0.8, in that it will estimate
number of reducers based on file size if parallelism is not specified for
join/group/etc operations. It's not using LoadStatistics afaik, that should
be fixed.

Ashutosh and I did some work around this about a year ago (on top of the
visitor madness) that was never really presentable.. would be happy to dig
up the code and see if any of it is still salvageable.

-D
On Thu, Oct 14, 2010 at 11:01 AM, Alan Gates wrote:

AFAIK no one is working on that currently. Our next thoughts on optimizer
improvement were to start using the new optimizer framework in the MR
optimizer so we can bring some order to the madness of visitors that is the
MR optimizer. I think Thejas plans on starting work on that in 0.9.

In the long run many people have discussed having a cost based optimizer,
but I have not seen any proposals of how it should work. With the advent of
Howl it would seem that at least basic statistic based decisions could be
made in the optimizer: is one of the files small enough to use a replicated
join in this case? is the file already sorted so we can use a merge join?.

It would be great if you're interested in working in this area. The best
way to start is file a JIRA or start a wiki page with general approach and
design information.

Alan.


On Oct 13, 2010, at 7:46 PM, Renato Marroquín Mogrovejo wrote:

Hey everyone!
In the Pig Journal page (http://wiki.apache.org/pig/PigJournal) says
something about getting statistics for Pig's optimizer. Is there any work
being done on that?
Or are there any other plans to improve the optimizer? I mean now is a
rule
based one, are there expectations to change it to a cost based one?
Any opinions or comments are highly appreciated. Thanks!


Renato M.

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