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From "Dag H. Wanvik (Commented) (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (DERBY-5546) ResultSet#updateBigDecimal on a REAL column does not do underflow checking
Date Fri, 16 Dec 2011 18:24:31 GMT

    [ https://issues.apache.org/jira/browse/DERBY-5546?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13171116#comment-13171116
] 

Dag H. Wanvik commented on DERBY-5546:
--------------------------------------

In SQLReal, the method setBigDecimal has this line:

   setValue(bigDecimal.floatValue());

The method BigDecimal.floatValue has this caveat in the Javadoc:
" Note that even when the return value is finite, this conversion can lose information about
the precision of the BigDecimal value. "

So, if the actual value is Double.MIN_VALUE, the value here is set to 0.0 without any error.
In contrast, when we try to update a DOUBLE column, the method used is

  setValue(bigDecimal.doubleValue())

This will not underflow, but subsequently gets caught by the range check in NumberDataType#normalizeDouble()
where the value is checked against Limits.DB2_SMALLEST_DOUBLE.

However, if the value represented in the BigDecimal is even smaller than Double.MIN_VALUE,
the call "bigDecimal.doubleValue()" would yield 0.0 and we would have the same behavior for
DOUBLE, too.


                
> ResultSet#updateBigDecimal on a REAL column does not do underflow checking
> --------------------------------------------------------------------------
>
>                 Key: DERBY-5546
>                 URL: https://issues.apache.org/jira/browse/DERBY-5546
>             Project: Derby
>          Issue Type: Bug
>          Components: JDBC
>    Affects Versions: 10.8.2.2
>            Reporter: Dag H. Wanvik
>            Priority: Minor
>         Attachments: MissingUnderflowCheck.java
>
>
> In contrast, ResultSet#updateBigDecimal on a FLOAT or DOUBLE column gives the expected
error on underflow. Cf. the attached repro program MissingUnderflowCheck.

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