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https://issues.apache.org/jira/browse/PIG-4662?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16026494#comment-16026494
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Rohini Palaniswamy commented on PIG-4662:
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bq. I'd like to see a modular design rather than intermingle different concept
together.
In that case we can extend and add a POJoinLocalRearrange that handles join
specific conditions like this. It would not be mixing up POLocalRearrange then.
bq. I don't feel it is hard to find the join key in the logical optimizer and
adding a filter on it.
Adding a extra filter operator for 3 lines of check will definitely impact
performance when we are dealing with billions of records. We recently had a
user who added is null bincond checks for lot of columns in his foreach which
dealt with 10+billions of records and it took extra 40+ minutes. Filter and
foreach are what we are trying to optimize in PIG-3764 with bytecode
generation. As we are trying to improve performance everywhere and trying to
save milliseconds we should not be doing this unless it is a major or
complicated change in which case it will be cleaner to keep it separate.
> 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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