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https://issues.apache.org/jira/browse/PIG-1178?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12803856#action_12803856
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Ying He commented on PIG-1178:
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Alan,thanks for the review.
for 6), the predecessor of LOFilter would be LOJoin, so all projections would
have input number 0. My algorithm is to get field names from column number.
The field names after join would be like A::id, B::id, And findCommon() is to
search for the longest prefix of these fields, to push filter to be after that
alias. For example, if field names are A::id, and A::value, the filter is
pushed after A. if field names are D::A::id and D::A::value, the filter can be
pushed after D, then pushed further to be after A.
> LogicalPlan and Optimizer are too complex and hard to work with
> ---------------------------------------------------------------
>
> Key: PIG-1178
> URL: https://issues.apache.org/jira/browse/PIG-1178
> Project: Pig
> Issue Type: Improvement
> Reporter: Alan Gates
> Assignee: Ying He
> Attachments: expressions-2.patch, expressions.patch, lp.patch,
> lp.patch, PIG_1178.patch
>
>
> The current implementation of the logical plan and the logical optimizer in
> Pig has proven to not be easily extensible. Developer feedback has indicated
> that adding new rules to the optimizer is quite burdensome. In addition, the
> logical plan has been an area of numerous bugs, many of which have been
> difficult to fix. Developers also feel that the logical plan is difficult to
> understand and maintain. The root cause for these issues is that a number of
> design decisions that were made as part of the 0.2 rewrite of the front end
> have now proven to be sub-optimal. The heart of this proposal is to revisit a
> number of those proposals and rebuild the logical plan with a simpler design
> that will make it much easier to maintain the logical plan as well as extend
> the logical optimizer.
> See http://wiki.apache.org/pig/PigLogicalPlanOptimizerRewrite for full
> details.
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