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https://issues.apache.org/jira/browse/PIG-3124?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13560304#comment-13560304
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Nick White commented on PIG-3124:
---------------------------------
Indeed - Daniel pointed out the code changes weren't necessary as this
optimisation is done by a different Rule. I've left a patch with comments to
that effect so it's clearer for the next person reading the code :)
> Push FLATTENs After FILTERs If Possible
> ---------------------------------------
>
> Key: PIG-3124
> URL: https://issues.apache.org/jira/browse/PIG-3124
> Project: Pig
> Issue Type: Improvement
> Components: impl
> Affects Versions: 0.10.0
> Reporter: Nick White
> Assignee: Nick White
> Fix For: 0.12
>
> Attachments: PIG-3124.0.patch, PIG-3124.1.patch
>
>
> When optimizing a logical plan, it's safe to push a FLATTEN after a FILTER if
> the columns being flattened don't occur in the expression that the filter is
> being done on. When the FILTER comes first the FLATTEN generates fewer rows
> (usually), and so is more efficient.
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