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Posted to user@pig.apache.org by Jonathan Coveney <jc...@gmail.com> on 2011/01/07 14:42:07 UTC
Re: Meaning of outputSchema - Python UDF
The words themselves have no meaning, as far as I know. What does matter is that its a touple with one element, a double. In the case of x:{etc}, the important thing is that pig knows it is a bag. The names are for us, not pig.
So in your own example, one function returns and actual bag, whereas the other only tuples (that may go inyo a bag).
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-----Original Message-----
From: <de...@wipro.com>
Date: Fri, 7 Jan 2011 18:29:03
To: <us...@pig.apache.org>
Reply-To: user@pig.apache.org
Subject: Meaning of outputSchema - Python UDF
Hi,
I don't seem to understand the OutputSchema constructs given in the documentation.
What is the significance of the letters 'x', 't', and the parentheses '{}' & '()'
@outputSchema("x:{t:(word:chararray)}")
For instance, the following looks different
#Percent- Percentage
@outputSchema("t:(percent:double)")
def percent(num, total):
return num * 100 / total
Apologies if my question sounds dumb.
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Re: Meaning of outputSchema - Python UDF
Posted by Julien Le Dem <le...@yahoo-inc.com>.
A couple of pointers:
UDFs must declare the schema of their output.
See the documentation here:
http://pig.apache.org/docs/r0.8.0/udf.html#Schema
In Java UDFs, this is done by implementing Schema outputSchema(Schema input)
In Python you use the @outputSchema decorator providing the schema in the format used in LOAD statements
See the schema documentation for reference:
http://pig.apache.org/docs/r0.8.0/piglatin_ref2.html#Schemas
Julien
On 1/7/11 5:42 AM, "Jonathan Coveney" <jc...@gmail.com> wrote:
The words themselves have no meaning, as far as I know. What does matter is that its a touple with one element, a double. In the case of x:{etc}, the important thing is that pig knows it is a bag. The names are for us, not pig.
So in your own example, one function returns and actual bag, whereas the other only tuples (that may go inyo a bag).
Sent via BlackBerry
-----Original Message-----
From: <de...@wipro.com>
Date: Fri, 7 Jan 2011 18:29:03
To: <us...@pig.apache.org>
Reply-To: user@pig.apache.org
Subject: Meaning of outputSchema - Python UDF
Hi,
I don't seem to understand the OutputSchema constructs given in the documentation.
What is the significance of the letters 'x', 't', and the parentheses '{}' & '()'
@outputSchema("x:{t:(word:chararray)}")
For instance, the following looks different
#Percent- Percentage
@outputSchema("t:(percent:double)")
def percent(num, total):
return num * 100 / total
Apologies if my question sounds dumb.
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