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Pig, mail # user - Loader partitioning on field


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Re: Loader partitioning on field
Rohini Palaniswamy 2013-03-14, 21:30
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!
> >>
>