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From "Knut Anders Hatlen (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (DERBY-5236) Client driver silently truncates strings that exceed 32KB
Date Fri, 01 Jul 2011 15:54:28 GMT

    [ https://issues.apache.org/jira/browse/DERBY-5236?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13058611#comment-13058611
] 

Knut Anders Hatlen commented on DERBY-5236:
-------------------------------------------

I think we could do that. I'll refresh the patch, as I think in its current form it might
have made some existing bad behaviour slightly worse. That is, if we get an overflow in the
length field, the string will be truncated even more than it was before. Perhaps we should
raise an exception in case of an overflow? Sounds better than silently returning the wrong
result, IMO.

By the way, I did a quick check of the DRDA spec back when I looked into this issue, and I
found some indications that this length field was supposed to contain the number of characters,
not the number of bytes. If that turns out to be the case, the two-byte field should be sufficient
for all VARCHARs with the current ~32K limit. Whether we can change the meaning of the length
field without breaking client/server compatibility is another question...

> Client driver silently truncates strings that exceed 32KB
> ---------------------------------------------------------
>
>                 Key: DERBY-5236
>                 URL: https://issues.apache.org/jira/browse/DERBY-5236
>             Project: Derby
>          Issue Type: Bug
>          Components: Network Client
>    Affects Versions: 10.8.1.2
>            Reporter: Knut Anders Hatlen
>         Attachments: repro.diff, write-full-string.diff
>
>
> Can be seen with this JUnit test case that retrieves a VARCHAR value with 20000 characters.
With the client driver, the string is truncated to 10900 characters (32700 bytes when encoded
in UTF-8).
>     public void testLongColumn() throws SQLException {
>         PreparedStatement ps = prepareStatement(
>                 "values cast(? as varchar(20000))");
>         char[] chars = new char[20000];
>         Arrays.fill(chars, '\u4e10');
>         String str = new String(chars);
>         ps.setString(1, str);
>         JDBC.assertSingleValueResultSet(ps.executeQuery(), str);
>     }

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