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From "Craig L Russell (JIRA)" <j...@apache.org>
Subject [jira] Commented: (JDO-643) avg return type
Date Fri, 17 Dec 2010 18:26:08 GMT

    [ https://issues.apache.org/jira/browse/JDO-643?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12972578#action_12972578

Craig L Russell commented on JDO-643:

What about the case where the JDO implementation lets the database perform the avg function?
If the database always returns a double value anyway, are we kidding ourselves that the result
is actually a BigDecimal? What should the precision be in this case?

Obviously, either the user or the implementation could take a double result and convert it
into a BigDecimal. Is there a good reason why BigDecimal is preferable to return to the user
instead of double? Would a user expect the result to be BigDecimal (without reading the JDO
specification carefully)? 

Is there a good enough reason for JDO to be different from JPA in this case?

> avg return type
> ---------------
>                 Key: JDO-643
>                 URL: https://issues.apache.org/jira/browse/JDO-643
>             Project: JDO
>          Issue Type: Bug
>          Components: specification
>    Affects Versions: JDO 2 maintenance release 2
>            Reporter: Guido Anzuoni
>            Assignee: Michael Bouschen
>             Fix For: JDO 3 maintenance release 1
>         Attachments: JDO-643.patch
> Aggregate type specification at page 175 claims that avg(expression) return type is the
same of the enclosed expression.
> This is wrong from a strictly mathematical point of view.
> In fact, if you select an avg on an int field member the result is truncated.
> The result type should always be double.

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