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From "Matthew Hayes" <matthew.terence.ha...@gmail.com>
Subject Re: Review Request 25564: DATAFU-69: Create SelectFieldByName UDF - which, given a field who's value contains a field name, and *, returns the value of the field referenced by the field name
Date Wed, 15 Oct 2014 15:01:49 GMT


> On Sept. 29, 2014, 12:56 a.m., Matthew Hayes wrote:
> >
> 
> Russell Jurney wrote:
>     Actually, I think renaming this to SelectStringFieldByName might make more sense.
The way this UDF is used, you are looking for a tag that identifies a group. These are almost
always chararrays. This doesn't limit the usefulness of the UDF at all.
> 
> Matthew Hayes wrote:
>     I like the new name ;)  I still think we need to have a schema for the output.  For
example, you could set the output schema to consist of a single chararray value and require
that all inputs be chararrays.  This should be simple to do for now.  If we find that this
is needed for other non-chararray cases we could relax the requirements.
> 
> Russell Jurney wrote:
>     Yeah, I agree. I'll have it return a chararray inside a tuple, in addition to changing
the name.

Okay sounds good. chararray in a tuple as the schema seems fine.  Also validate in getSchema
that the inputs are chararray as well.


- Matthew


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This is an automatically generated e-mail. To reply, visit:
https://reviews.apache.org/r/25564/#review54788
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On Oct. 2, 2014, 4:19 p.m., Russell Jurney wrote:
> 
> -----------------------------------------------------------
> This is an automatically generated e-mail. To reply, visit:
> https://reviews.apache.org/r/25564/
> -----------------------------------------------------------
> 
> (Updated Oct. 2, 2014, 4:19 p.m.)
> 
> 
> Review request for DataFu, Jonathan Coveney, Jakob Homan, Matthew Hayes, and Sam Shah.
> 
> 
> Repository: datafu
> 
> 
> Description
> -------
> 
> Example use:
> group_fields = LOAD '/e8/smalldata/group_fields.txt' AS (groupField:chararray); 
> with_group = CROSS group_fields, hour_rounded;
> with_group = FOREACH with_group GENERATE group_fields::groupField AS groupField, 
> hour_rounded::sourceNameOrIp AS sourceNameOrIp,
> hour_rounded::destinationNameOrIp AS destinationNameOrIp,
> ...;
> with_value_substitution = FOREACH with_group GENERATE ChooseFieldByValue(groupField,
*) AS groupValue:tuple(value:chararray), *;
> with_value_substitution = FOREACH with_value_substitution GENERATE 
> FLATTEN(groupValue) AS groupValue:chararray,
> groupField,
> foo,
> bar,
> ...;
> all_success = FOREACH (GROUP with_value_substitution BY (groupField, groupValue, day))
GENERATE
> FLATTEN(group) AS (seriesType, groupValue, day),
> (int)COUNT_STAR(with_value_substitution) AS connections:int;
> 
> 
> Diffs
> -----
> 
>   datafu-pig/src/main/java/datafu/pig/util/SelectFieldByName.java PRE-CREATION 
>   datafu-pig/src/test/java/datafu/test/pig/util/SelectFieldByNameTest.java PRE-CREATION

> 
> Diff: https://reviews.apache.org/r/25564/diff/
> 
> 
> Testing
> -------
> 
> This UDF was used to replace a very inefficient pig script where macros that did many
individual GROUP BY's took many minutes to plan.
> 
> Testing: unit tests and used on real data on a cluster.
> 
> 
> Thanks,
> 
> Russell Jurney
> 
>


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