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https://issues.apache.org/jira/browse/PIG-627?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Richard Ding updated PIG-627:
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Attachment: multiquery-phase2_0323.patch
Thanks for reviewing the patch.
In MultiQueryOptimizer:
* what about mr not being map only and with mr splittee? - is this not
handled for now?
_Yeah. There are two cases where splittees will not be merged into
splitter: (1) splitter is not map only and splittee has reducer, and (2)
splittee has multiple roots (loads)_
* Is the single mapper case and the single map-reduce case when the script
has an explicit store 'file' and load 'file' - if this is so, then in
mergeOnlyMapperSplittee() and mergeOnlyMapReduceSplittee(), the store is
removed - shouldn't the store remain?
_Explicit store/load combination in a script is transformed into an
implicit split, hence the store remains_
* There is common code in mergeOnlyMapperSplittee() and
meregOnlyMapReduceSplittee() which should be moved to a function to reduce the
code duplication.
_Fixed_
Just want to confirm that the multi query optimization is only for map reduce
mode - since the optimizer is being called in MapReduceLauncher
_Yes_
In POForEach when there is POStatus.STATUS_ERR, it is returned to the caller. I
noticed that in POSplit, it causes an exception - I think it should return the
error whhic would later be caught in the map() or reduce() - a test to make
sure errors do get caught and cause failures would be good.
_Fixed_
spawnChildWalker() of ReverseDependencyOrderWalker should return an instance of
ReverseDependencyWalker.
_Fixed_
> PERFORMANCE: multi-query optimization
> -------------------------------------
>
> Key: PIG-627
> URL: https://issues.apache.org/jira/browse/PIG-627
> Project: Pig
> Issue Type: Improvement
> Affects Versions: 1.0.0
> Reporter: Olga Natkovich
> Attachments: file_cmds-0305.patch, multi-store-0303.patch,
> multi-store-0304.patch, multiquery-phase2_0313.patch,
> multiquery-phase2_0323.patch, multiquery_0223.patch, multiquery_0224.patch,
> multiquery_0306.patch, multiquery_explain_fix.patch
>
>
> Currently, if your Pig script contains multiple stores and some shared
> computation, Pig will execute several independent queries. For instance:
> A = load 'data' as (a, b, c);
> B = filter A by a > 5;
> store B into 'output1';
> C = group B by b;
> store C into 'output2';
> This script will result in map-only job that generated output1 followed by a
> map-reduce job that generated output2. As the resuld data is read, parsed and
> filetered twice which is unnecessary and costly.
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