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https://issues.apache.org/jira/browse/PIG-2831?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13427036#comment-13427036
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Prasanth J commented on PIG-2831:
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Ya. I could do that. Looks like this will need a separate map job for reading
few tuples? I think this will require tweaking the loader to emit a special
tuple with the estimated number of records.
I will try that once the end to end base implementation is up. For now the way
I am counting the sample size is by using RandomSampleLoader. I am sampling
1000 tuples per mapper and using that samples for naive computation and
determining the partition size. But RandomSampleLoader always returns more
samples than expected. Not sure if its a bug!!. Once the complete
implementation is done we can look into more accurate estimate of number of
tuples etc. Will soon submit an intermediate patch for review.
Also given the in-memory size of a tuple, how can we estimate the number of
tuples that a reducer can handle without spilling to disk?
> MR-Cube implementation (Distributed cubing for holistic measures)
> -----------------------------------------------------------------
>
> Key: PIG-2831
> URL: https://issues.apache.org/jira/browse/PIG-2831
> Project: Pig
> Issue Type: Sub-task
> Reporter: Prasanth J
> Assignee: Prasanth J
>
> Implementing distributed cube materialization on holistic measure based on
> MR-Cube approach as described in http://arnab.org/files/mrcube.pdf.
> Primary steps involved:
> 1) Identify if the measure is holistic or not
> 2) Determine algebraic attribute (can be detected automatically for few
> cases, if automatic detection fails user should hint the algebraic attribute)
> 3) Modify MRPlan to insert a sampling job which executes naive cube algorithm
> and generates annotated cube lattice (contains large group partitioning
> information)
> 4) Modify plan to distribute annotated cube lattice to all mappers using
> distributed cache
> 5) Execute actual cube materialization on full dataset
> 6) Modify MRPlan to insert a post process job for combining the results of
> actual cube materialization job
> 7) OOM exception handling
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