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From Gabriel Reid <gabriel.r...@gmail.com>
Subject Re: Generic class for converting PCollection to PTable
Date Thu, 20 Feb 2014 12:01:11 GMT
On Thu, Feb 20, 2014 at 11:59 AM, Jinal Shah <jinalshah2007@gmail.com> wrote:
> Somewhat like that as we are also using that same approach but I was more
> thinking of it as
> PTables.asPTable(PCollection<V>, Keyfinder<V>, PType<K>) and return
as
> PTable<K,V>
>
> Basically
> KeyFinder<V> is an interface which will have somekind of method like
> findKey(V) returning K from that V or calculated or anyway it wants.
>

This is pretty much exactly what PCollection#by does. Your proposed
method as you described it would be written as follows using
PCollection#by:

    PCollection<V> collection = ...;
    PTable<K, V> table = collection.by(new KeyFinderMapFn(), ptypeForKey);


The method is described at
http://crunch.apache.org/apidocs/0.8.2/org/apache/crunch/PCollection.html#by(org.apache.crunch.MapFn,%20org.apache.crunch.types.PType)

- Gabriel



>
>
> On Thu, Feb 20, 2014 at 12:07 AM, Gabriel Reid <gabriel.reid@gmail.com>wrote:
>
>>
>>
>> > On 20 Feb 2014, at 05:11, Jinal Shah <jinalshah2007@gmail.com> wrote:
>> >
>> > I didn't knew that, but I was more talking about something like this
>> > PCollection<V> to  PTable<K,V> basically.
>> >
>>
>> I think what you want is the PCollection#by method. It takes a MapFn that
>> maps each value V to a key, and returns a PTable<K,V>
>>
>> - Gabriel
>>
>> >
>> >
>> >> On Wed, Feb 19, 2014 at 5:49 PM, Josh Wills <jwills@cloudera.com>
>> wrote:
>> >>
>> >> org.apache.crunch.lib.PTables.asPTable is likely what you want.
>> >>
>> >>
>> >> On Wed, Feb 19, 2014 at 3:47 PM, Jinal Shah <jinalshah2007@gmail.com>
>> >> wrote:
>> >>
>> >>> Hi everyone,
>> >>>
>> >>> Is there a generic way of converting PCollection to PTable? If not,
Can
>> >> we
>> >>> create a generic class? Because we are having lot of places where we
>> want
>> >>> to perform a join on 2 PCollections so we have to convert it into
>> PTables
>> >>> and then do a join and then convert it into a PCollection. So i was
>> >>> wondering is there a better way of doing this.
>> >>>
>> >>> Thanks
>> >>
>> >>
>> >>
>> >> --
>> >> Director of Data Science
>> >> Cloudera <http://www.cloudera.com>
>> >> Twitter: @josh_wills <http://twitter.com/josh_wills>
>> >>
>>

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