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From Brock Noland <br...@cloudera.com>
Subject Re: CombineFn vs. Aggregator
Date Fri, 02 Nov 2012 18:42:53 GMT
Like a bear awoken from a slumber...inline.

On Fri, Nov 2, 2012 at 12:44 PM, Josh Wills <jwills@cloudera.com> wrote:
> +brock explicitly
>
> Brock, do you remember why we did AggregatorFactory? It was like a year ago,
> and I can't remember if there was some additional reason for it or if I just
> did the impl without thinking the problem through.
>
> J
>
> On Fri, Nov 2, 2012 at 9:53 AM, Matthias Friedrich <matt@mafr.de> wrote:
>>
>> On Friday, 2012-11-02, Josh Wills wrote:
>> > On Fri, Nov 2, 2012 at 3:13 AM, Matthias Friedrich <matt@mafr.de> wrote:
>> > Pair<Double, Double>> can't reuse the same SUM_DOUBLE aggregator for
>> > both
>> > values of the Pair instance.
>>
>> Hmm, I'm not sure if that's something we need to prevent actively.
>> Users will probably write it like this:
>>
>>   PGroupedTable<String, Pair<Integer, Integer>> table = /* ... */;
>>   table.combineValues( pairAggregator(SUM_INTS(), SUM_INTS()) );
>>

Without the factory or a similar concept, this wouldn't work, right?
Meaning that if all we did was eliminate the factory, then there would
be a single SumInts object ClassLoader wide. Has the implementation
changed so much my comments are out of date?

Brock

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