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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