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Pig, mail # user - Loader partitioning on field


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Jeff Yuan 2013-03-14, 20:31
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Rohini Palaniswamy 2013-03-14, 20:51
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Jeff Yuan 2013-03-14, 21:00
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Rohini Palaniswamy 2013-03-14, 21:30
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Jeff Yuan 2013-03-14, 22:03
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Re: Loader partitioning on field
Jonathan Coveney 2013-03-14, 22:15
No, it is not. But if it knew that, how would that filter be meaningful?
What do you have in mind?
2013/3/14 Jeff Yuan <[EMAIL PROTECTED]>

> Rohini, I see your point.
>
> One followup question: it's possible for the result of a UDF to be
> constant and not dependent on the tuples of each record, right? Is Pig
> able to make such a determination in this case and push the pushdown
> such UDF results to load?
>
> Thanks,
> Jeff
>
> On Thu, Mar 14, 2013 at 2:30 PM, Rohini Palaniswamy
> <[EMAIL PROTECTED]> wrote:
> > The filter push down to LoadFunc happens on the front end before the job
> > launch and the UDF is still not evaluated then. So you need to have
> > constants in your filter condition.
> >
> > Logical plan is internal to pig and will never be exposed. Refer
> > https://issues.apache.org/jira/browse/PIG-3199
> >
> > Regards,
> > Rohini
> >
> >
> > On Thu, Mar 14, 2013 at 2:00 PM, Jeff Yuan <[EMAIL PROTECTED]>
> wrote:
> >
> >> Thanks! Regarding 1), where there is a UDF in the filter step on a
> >> partition field. The UDF is not first evaluated before and then the
> >> result passed to the load function?
> >>
> >> A separate question: In a LoadFunc, is there a way to get a reference
> >> to the logical query plan?
> >>
> >> Thanks again.
> >>
> >> On Thu, Mar 14, 2013 at 1:51 PM, Rohini Palaniswamy
> >> <[EMAIL PROTECTED]> wrote:
> >> > Jeff,
> >> >
> >> > 1) It should not. If it does push, then it is a bug in pig.
> >> >
> >> > 2) I think it should be fine.
> >> >
> >> > 3) Look at PColFilterExtractor and PartitionFilterOptimizer
> >> >
> >> > Regards,
> >> >
> >> > Rohini
> >> >
> >> >
> >> > On Thu, Mar 14, 2013 at 1:31 PM, Jeff Yuan <[EMAIL PROTECTED]>
> >> wrote:
> >> >
> >> >> I am writing a loader for a storage format, which partitions by a
> >> >> particular field in the record. So I would like to implement
> something
> >> >> which can push down filters on the partitioned field so that the
> >> >> record reader does not need to read files that are outside the
> >> >> filtered range. In the interface "LoadMetadata", the
> >> >> "getPartitionKeys" and "setPartitionFilter" functions seem to support
> >> >> what I need (where Pig should pass the filtering expression on the
> >> >> declared partition keys to "setPartitionFilter", but I have a couple
> >> >> of questions. I'm going to reference the following example, where
> >> >> timestamp is the partition key.
> >> >>
> >> >> a = load 'stored_data' using CustomLoader();
> >> >> b = filter a by timestamp = CUSTOM_UDF(date, month);
> >> >>
> >> >> 1. Would partitioning work in this case where the partition key
> filter
> >> >> includes a UDF?
> >> >>
> >> >> 2. Does the partition statement need to be directly after the load
> >> >> statement? What I mean is, if I declare a variable c between a and b
> >> >> which does some other operation on a, will Pig pass the filter
> >> >> expression of b when loading a?
> >> >>
> >> >> 3. Can you point out roughly where this "setPartitionFilter" function
> >> >> is called in Pig code during the load process? I couldn't seem to
> find
> >> >> it through a search of the Pig source.
> >> >>
> >> >> Thanks a lot!
> >> >>
> >>
>
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Jeff Yuan 2013-03-14, 22:56
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Jonathan Coveney 2013-03-15, 10:17