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https://issues.apache.org/jira/browse/PIG-1014?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12766069#action_12766069
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Dmitriy V. Ryaboy commented on PIG-1014:
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A link that talks about some of the more "interesting" behaviors of NULL in 
SQL: http://thoughts.j-davis.com/2009/08/02/what-is-the-deal-with-nulls/

The difference between COUNT and COUNT_STAR is that COUNT_STAR counts nulls. I 
think this ticket boils down to the question, "what do we consider a null 
tuple?".  At the moment, we consider A.$0 to determine whether the tuple is 
null; that doesn't seem right, and surprises users. We have two options that 
both make sense -- a null tuple is a tuple in which all fields are null, or a 
null tuple is a tuple which is completely null (ie, doesn't even have any 
fields).  I am in favor of the first definition, which is a superset of the 
second.

> Pig should convert COUNT(relation) to COUNT_STAR(relation) so that all 
> records are counted without considering nullness of the fields in the records
> ----------------------------------------------------------------------------------------------------------------------------------------------------
>
>                 Key: PIG-1014
>                 URL: https://issues.apache.org/jira/browse/PIG-1014
>             Project: Pig
>          Issue Type: Bug
>    Affects Versions: 0.4.0
>            Reporter: Pradeep Kamath
>


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