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https://issues.apache.org/jira/browse/PIG-1337?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12852445#action_12852445
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Chao Wang commented on PIG-1337:
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It's ok for us not to use getSchema() for this purpose since it's a pure getter
method.
What we need is simply a setter method in LoadFunc through which we can set up
distributed cache. Pig needs to ensure that this information is indeed in the
job configuration variable that's being passed to hadoop backend.
Also, this setter method should be only invoked at Pig's frondend. In the case
of one m/r job containing multiple LoadFunc instances, Pig may need to combine
distributed cache configuration information from all instances.
Also, we note that using the UDFContext to convey information from frontend to
backend is not working for this. We need the job configuration variable
already contain all the distributed cache related information when it's being
passed to the hadoop backend.
> Need a way to pass distributed cache configuration information to hadoop
> backend in Pig's LoadFunc
> --------------------------------------------------------------------------------------------------
>
> Key: PIG-1337
> URL: https://issues.apache.org/jira/browse/PIG-1337
> Project: Pig
> Issue Type: Improvement
> Affects Versions: 0.6.0
> Reporter: Chao Wang
> Fix For: 0.8.0
>
>
> The Zebra storage layer needs to use distributed cache to reduce name node
> load during job runs.
> To to this, Zebra needs to set up distributed cache related configuration
> information in TableLoader (which extends Pig's LoadFunc) .
> It is doing this within getSchema(conf). The problem is that the conf object
> here is not the one that is being serialized to map/reduce backend. As such,
> the distributed cache is not set up properly.
> To work over this problem, we need Pig in its LoadFunc to ensure a way that
> we can use to set up distributed cache information in a conf object, and this
> conf object is the one used by map/reduce backend.
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