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From "George Mavromatis (JIRA)" <j...@apache.org>
Subject [jira] Created: (PIG-767) Schema reported from DESCRIBE and actual schema of inner bags are different.
Date Thu, 16 Apr 2009 04:45:15 GMT
Schema reported from DESCRIBE and actual schema of inner bags are different.
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                 Key: PIG-767
                 URL: https://issues.apache.org/jira/browse/PIG-767
             Project: Pig
          Issue Type: Bug
            Reporter: George Mavromatis
             Fix For: 0.2.0



The following script:

urlContents = LOAD 'inputdir' USING BinStorage() AS (url:bytearray, pg:bytearray);
-- describe and dump are in-sync
DESCRIBE urlContents;
DUMP urlContents;

urlContentsG = GROUP urlContents BY url;
DESCRIBE urlContentsG;

urlContentsF = FOREACH urlContentsG GENERATE group,urlContents.pg;

DESCRIBE urlContentsF;
DUMP urlContentsF;


Prints for the DESCRIBE commands:

urlContents: {url: chararray,pg: chararray}
urlContentsG: {group: chararray,urlContents: {url: chararray,pg: chararray}}
urlContentsF: {group: chararray,pg: {pg: chararray}}

The reported schemas for urlContentsG and urlContentsF are wrong. They are also against the
section "Schemas for Complex Data Types" in http://wiki.apache.org/pig-data/attachments/FrontPage/attachments/plrm.htm#_Schemas.

As expected, actual data observed from DUMP urlContentsG and DUMP urlContentsF do contain
the tuple inside the inner bags.

The correct schema for urlContentsG is:  {group: chararray,urlContents: {t1:(url: chararray,pg:
chararray)}}

This may sound like a technicality, but it isn't. For instance, a UDF that assumes an inner
bag of {chararray} will not work with {(chararray)}. 





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