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https://issues.apache.org/jira/browse/PIG-873?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12892595#action_12892595
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Daniel Dai commented on PIG-873:
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Talked with Santhosh. This issue is to allow a special patten like ForEach* ->
Join, means any number of ForEach connected to Join. It is not yet in new
logical framework.
> Optimizer should allow search for global patterns
> -------------------------------------------------
>
> Key: PIG-873
> URL: https://issues.apache.org/jira/browse/PIG-873
> Project: Pig
> Issue Type: Improvement
> Affects Versions: 0.4.0
> Reporter: Santhosh Srinivasan
> Assignee: Daniel Dai
> Fix For: 0.8.0
>
>
> Currently, the optimizer works on the following mechanism:
> 1. Specify the pattern to be searched
> 2. For each occurrence of the pattern, check and then apply a transformation
> With this approach, the search for a pattern is localized. An example will
> illustrate the problem.
> If the pattern to be searched for is foreach (with flatten) connected to any
> operator and if the graph has more than one foreach (with flatten) connected
> to an operator (cross, join, union, etc), then each instance of foreach
> connected to the operator is returned as a match. While this is fine for a
> localized view (per match), at a global view the pattern to be searched for
> is any number of foreach connected to an operator.
> The implication of not having a globalized view is more rules. There will be
> one rule for one foreach connected to an opeator, one rule for two foreachs
> connected to an operators, etc.
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