You absolutely can do this, I'm just not sure if you can do it using the
accumulator interface (I THINK you can, as I think it ratchets only the
first tuple input, and passes the entire second one, but am not sure,
someone else can weigh in). If you CAN do it with the accumulator interface
though I highly recommend it, as it's more memory efficient.
Basicaly, you'll have this as your pig script:
public class doublebag {
public <OutputType> exec(Tuple input) throws IOException {
DataBag innerBag = (DataBag)input.get(0);
DataBag outerBag = (DataBag)input.get(1);
Iterator<Tuple> ibit = innerBag.iterator();
while (ibit.hasNext()) {
Tuple ibelem = ibit.next();
Iterator<Tuple> obit = outerBag.iterator();
while (obit.hasNext()) {
Tuple obelem = obit.next();
}
}
}
}
Obviously, you need to do things like checking for empty input etc etc, this
is just a rough rough example of the code. The point is, if you just do
exec, you'll simply have a bag as your first input and a bag as the second.
And then in your code if you want to do one entire bag against another,
you'd just do a group thing all; and pass it that thing.
Hope that explanation made sense, if it didn't just ask again. It's worth
going over the bag->bag example in the UDF manual, and really, you just have
2 bag inputs instead of one.
2011/1/13 <deepak....@wipro.com>
> Hi,
>
> I wish to pass an outer bag into a Python UDF.
>
> Something like:
>
> Calculation-data = LOAD /path/to/data AS (field;int);
> Actual_data = LOAD /path/to/data AS (field1:int, field2:int)
>
>
> Calculation_data is not a very big bag. Maybe about 500 tuples in all - a
> single file.
> Actual_data is the real data source lying on HDFS.
>
> For each tuple in Actual_data, I wish to have the entire Calculation_data
> (whole bag) for some calculation that I wish to do.
>
> So, with every call to a UDF, I need to pass this bag along with tuple from
> Actual_data.
>
> Simply, is there any way of passing an outer bag into a Python UDF?
>
> Regards,
> Deepak
> Please do not print this email unless it is absolutely necessary.
>
> The information contained in this electronic message and any attachments to
> this message are intended for the exclusive use of the addressee(s) and may
> contain proprietary, confidential or privileged information. If you are not
> the intended recipient, you should not disseminate, distribute or copy this
> e-mail. Please notify the sender immediately and destroy all copies of this
> message and any attachments.
>
> WARNING: Computer viruses can be transmitted via email. The recipient
> should check this email and any attachments for the presence of viruses. The
> company accepts no liability for any damage caused by any virus transmitted
> by this email.
>
> www.wipro.com
>
