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From "Pradeep Kamath (JIRA)" <j...@apache.org>
Subject [jira] Commented: (PIG-627) PERFORMANCE: multi-query optimization
Date Wed, 11 Mar 2009 23:14:50 GMT

    [ https://issues.apache.org/jira/browse/PIG-627?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12681085#action_12681085
] 

Pradeep Kamath commented on PIG-627:
------------------------------------

Committed patch per previous comment that the review comments will be addressed in the next
patch - thanks Richard for the contribution. 

In general from Pig code we always want to throw known PigExceptions even for programming
errors or internal state errors - in these cases, we just use the source of the Exception
as PigExcetion.BUG. RuntimeException should be used when we want to throw an exception in
a function which cannot throw any exceptions (like in methods from Hadoop API which we are
implementing which do not throw any Exception)

> 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_0223.patch, multiquery_0224.patch, multiquery_0306.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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