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From "Pawel Fronczak (Commented) (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (DERBY-5489) getBinary() returns incorrect data after getObject() call on BLOB column
Date Tue, 01 Nov 2011 17:11:34 GMT

    [ https://issues.apache.org/jira/browse/DERBY-5489?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13141336#comment-13141336
] 

Pawel Fronczak commented on DERBY-5489:
---------------------------------------

The problem with changing the code responsible for the data retrieval is that it is part of
the SpringFramework library. Since it seems that it is opposing the JDBC API, I shall file
a bug report for that.

Fortunately, there is a simple workaround - instead of using the queryForList() method, one
could use the query() method and supply custom RowMapper (or RowCallbackHandler) which will
read the BLOB column only once.

Nevertheless, an exception from getBytes explaining what has happened would be very helpful.
Right now it is not very easy to track down the cause of the problem.
                
> getBinary() returns incorrect data after getObject() call on BLOB column
> ------------------------------------------------------------------------
>
>                 Key: DERBY-5489
>                 URL: https://issues.apache.org/jira/browse/DERBY-5489
>             Project: Derby
>          Issue Type: Bug
>          Components: JDBC
>    Affects Versions: 10.7.1.1, 10.8.2.2
>            Reporter: Pawel Fronczak
>         Attachments: SelectBlobBug.java
>
>
> When ResultSet.getObject(int) is called on a BLOB column, the correct EmbedBlob object
is returned. But if afterwards the ResultSet.getBytes(int) is called on the same row, the
returned array contains invalid data - it is offset by 3 bytes and its size is incorrect.
> The problem only occurs when the stored BLOB is large enough to be internally represented
by stream and not by array of bytes (at least ~32KiB).
> It seems that the getObject method shifts the stream position and therefore the getBytes
method starts to read the data after the third byte, thus incorrectly calculating its length.

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