Olga Natkovich commented on PIG-627:

I committed the latest patch. Ran the unit tests and they all passed.

Couple of issues that need to be addressed:

(1) PigServer.openIterator, in batch mode, always returns an empty iterator. 
That will not work if a script has a dump in it.
(2) PigSever.getStorePlan assumes that each alias maps to a single store. In 
case of multiple queries that might not be true.

Thanks Richard and Gunther for your contribution!

> PERFORMANCE: multi-query optimization
> -------------------------------------
>                 Key: PIG-627
>                 URL: https://issues.apache.org/jira/browse/PIG-627
>             Project: Pig
>          Issue Type: Improvement
>    Affects Versions: types_branch
>            Reporter: Olga Natkovich
>             Fix For: types_branch
>         Attachments: multiquery_0223.patch, multiquery_0224.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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