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Pig, mail # user - conditional and multiple generate inside foreach?


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Re: conditional and multiple generate inside foreach?
Dexin Wang 2011-07-23, 01:10
Thanks. I'm not familiar with python, but I write bunch of UDFs in java.

One question though, how do I pass the the entire tuple to the UDF, I mean I
can't do something like this:

    B = FOREACH A GENERATE myudf(A)

Essentially what I want is given a tuple, I want to enrich the tuple to add
one more field to it, and the value of the new field depends on the value in
some existing fields in the tuple.

(a,1) -> (a,1,yesterday)

how would I do that?

I imagine I can do
   B = GROUP A BY random;
   C = FOREACH B GENERATE myudf(A);

But I really don't like adding another GROUP BY here.

On Fri, Jul 22, 2011 at 5:23 PM, Scott Foster <[EMAIL PROTECTED]>wrote:

> Hi Dexin,
> This is the sort of thing I've started using Python UDFs for. See:
> http://wiki.apache.org/pig/UDFsUsingScriptingLanguages for examples of
> how to write the python code.
>
> If your udf was implemented in Python you could then do this...
>
> register 'udfs.py' using jython as udf;
> ...
> B = FOREACH A generate name, udf.daysAgoString(days_ago);
>
> scott.
>
> On Fri, Jul 22, 2011 at 4:42 PM, Dexin Wang <[EMAIL PROTECTED]> wrote:
> > Possible to do conditional and more than one generate inside a foreach?
> >
> > for example, I have tuples like this (names, days_ago)
> >
> > (a,0)
> > (b,1)
> > (c,9)
> > (d,40)
> >
> > b shows up 1 day ago, so it belongs to all of the following: yesterday,
> last
> > week, last month, and last quarter. So I'd like to turn the above to:
> >
> > (a,0,today)
> > (b,1,yesterday)
> > (b,1,week)
> > (b,1,month)
> > (b,1,quarter)
> > (c,9,month)
> > (c,9,quarter)
> > (d,40,quarter)
> >
> > I imagine/dream I could do something like this
> >
> > B = FOREACH A
> >  {
> >        if (days_ago <= 90) generate name,days_ago,'quarter';
> >        if (days_ago <= 30) generate name,days_ago,'month';
> >        if (days_ago <= 7)   generate name,days_ago,'week';
> >        if (days_ago == 1)   generate name,days_ago,'yesterday';
> >        if (days_ago == 0)   generate name,days_ago,'today';
> >  }
> >
> > of course that's not valid syntax. I could write my own UDF but would be
> > nice there's some way to get what I want without UDF.
> >
> > Thanks!
> > Dexin
> >
>