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https://issues.apache.org/jira/browse/PIG-4662?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16024192#comment-16024192
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Daniel Dai commented on PIG-4662:
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I prefer to do it in optimizer, it seems to be more clear.
> New optimizer rule: filter nulls before inner joins
> ---------------------------------------------------
>
> Key: PIG-4662
> URL: https://issues.apache.org/jira/browse/PIG-4662
> Project: Pig
> Issue Type: Improvement
> Reporter: Ido Hadanny
> Assignee: Satish Subhashrao Saley
> Priority: Minor
> Labels: Performance
> Fix For: 0.18.0
>
>
> As stated in the docs, rewriting an inner join and filtering nulls from
> inputs can be a big performance gain:
> http://pig.apache.org/docs/r0.14.0/perf.html#nulls
> We would like to add an optimizer rule which detects inner joins, and filters
> nulls in all inputs:
> A = filter A by t is not null;
> B = filter B by x is not null;
> C = join A by t, B by x;
> see also:
> http://stackoverflow.com/questions/32088389/is-the-pig-optimizer-filtering-nulls-before-joining
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