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From "Patel,Stephen" <Stephen.Pa...@Cerner.com>
Subject Re: ExtractKeyFn scaleFactor seems to be incorrect
Date Thu, 21 May 2015 21:54:08 GMT
Thanks!

https://issues.apache.org/jira/browse/CRUNCH-525

From: Josh Wills <josh.wills@gmail.com<mailto:josh.wills@gmail.com>>
Reply-To: "user@crunch.apache.org<mailto:user@crunch.apache.org>" <user@crunch.apache.org<mailto:user@crunch.apache.org>>
Date: Thursday, May 21, 2015 2:42 PM
To: "user@crunch.apache.org<mailto:user@crunch.apache.org>" <user@crunch.apache.org<mailto:user@crunch.apache.org>>
Subject: Re: ExtractKeyFn scaleFactor seems to be incorrect

Yes, you're right-- file a JIRA for it?

J

On Thu, May 21, 2015 at 10:48 AM, Patel,Stephen <Stephen.Patel@cerner.com<mailto:Stephen.Patel@cerner.com>>
wrote:
I was looking at the PCollectionImpl.by method[0] today, and I think that the ExtractKeyFn[1]
it's using may not be calculating scaleFactor correctly.  The ExtractKeyFn is using the default
scaleFactor for a MapFn (1.0), but shouldn't it have a scaleFactor of 1 + the input MapFn's
scaleFactor?

As an example, if you had a Pcollection<T> and you call by with the IdentifyFn, the
returned table should have a size of 2 * the original collections size, but as it stands now,
it will have the same size as the original.

Assuming we later group a table that we constructed with by, won't we use (potentially) far
fewer reducers than we actually should be?

[0]: https://github.com/apache/crunch/blob/master/crunch-core/src/main/java/org/apache/crunch/impl/dist/collect/PCollectionImpl.java#L270<https://urldefense.proofpoint.com/v2/url?u=https-3A__github.com_apache_crunch_blob_master_crunch-2Dcore_src_main_java_org_apache_crunch_impl_dist_collect_PCollectionImpl.java-23L270&d=AwMFaQ&c=NRtzTzKNaCCmhN_9N2YJR-XrNU1huIgYP99yDsEzaJo&r=heMtsNUnSvUNkLr3-_z5d3hBAgWghswOidN-QwCMKOk&m=MIr3Gvh_tC1PfkWs0o2CVQxCkz7BzF4hXL0ULzTs644&s=M4RAGjb1kRqQWHLyOhCfA5gP7u5aMsr0G26_b364Dnw&e=>
[1]: https://github.com/apache/crunch/blob/master/crunch-core/src/main/java/org/apache/crunch/fn/ExtractKeyFn.java<https://urldefense.proofpoint.com/v2/url?u=https-3A__github.com_apache_crunch_blob_master_crunch-2Dcore_src_main_java_org_apache_crunch_fn_ExtractKeyFn.java&d=AwMFaQ&c=NRtzTzKNaCCmhN_9N2YJR-XrNU1huIgYP99yDsEzaJo&r=heMtsNUnSvUNkLr3-_z5d3hBAgWghswOidN-QwCMKOk&m=MIr3Gvh_tC1PfkWs0o2CVQxCkz7BzF4hXL0ULzTs644&s=xAZsOsj7-jZVJYkT2IukxGB8L0Jaf04o04UPEOWf-wQ&e=>
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