THE SCENARIO:
I've got a database that uses fixed size keys (16 bytes) and variable
size values. The database is configured for BTREE and duplicates. To
extract the duplicates for a given key I use a Dbc and loop until I've
grabbed all the duplicates.

THE PROBLEM:
Whenever I create a Dbt object (as the key) and set the DB_DBT_USERMEM
flag, after the initial Dbc.get, subsequent gets throws a DbException
saying:
<quote-snippet>
Dbt not large enough for available data
at com.sleepycat.db.db_javaJNI.Dbc_get__SWIG_0(Native Method)
at com.sleepycat.db.Dbc.get(Dbc.java:791)
....
</quote-snippet>

I'm including the code of the method that causes the problem

<code>
public Collection<String> get( long k ) throws IOException
{
Collection<String> c = null;
Utf8StringDbt data = new Utf8StringDbt();
// Converts k to a Dbt by prefixing it w/ its parent key
Dbt key = convert( k );
key.setFlags( Db.DB_DBT_USERMEM );
try
{
Dbc cursor = bdDb.getBerkleyDb( dbName ).cursor( null, 0 );
try
{
if( 0 == cursor.get( key, data, Db.DB_SET ) )
{
c = new LinkedList<String>();
do
c.add( data.toString() );
while( 0 == cursor.get( key, data, Db.DB_NEXT_DUP ) );
}
}
finally
{
cursor.close();
}
}
catch( DbException e )
{
throw new RuntimeException( e );
}
return c;
}
</code>

If I remove the call to setFlag the error goes away. I know the keys
are only 16 bytes wide. I've even written debugging code where the key
used in the [while] loop is a freshly created Dbt. After each
iteration of the loop I print [to stderr] the offset and size of the
Dbt. It's always 0 and 16 respectively. In a moment of utter
frustration I modified the convert method to create a Dbt w/ a size of
1024 bytes, more than enough for even the data, but I still get the
Exception complaining about not big enough. Why won't Berkeley DB
accept my 'static' key?

--Sysconfig--
Hardware: Dell Inspiron 8500
Arch: Intel Pentium 4M 2.2GHz
Mem: 1.5GB
Disk: 80GB
O.S: Gentoo Linux
Kernel: 2.6.8.1
GLIBC:
GNU C Library stable release version 2.3.3, by Roland McGrath et al.
Compiled by GNU CC version 3.3.3 20040412 (Gentoo Linux 3.3.3-r6,
ssp-3.3.2-2, pie-8.7.6).
Compiled on a Linux 2.6.7 system on 2004-08-09.
Available extensions:
GNU libio by Per Bothner
crypt add-on version 2.1 by Michael Glad and others
NPTL 0.61 by Ulrich Drepper
BIND-8.2.3-T5B
NIS(YP)/NIS+ NSS modules 0.19 by Thorsten Kukuk
Thread-local storage support included.
Report bugs using the `glibcbug' script to <bugs (AT) gnu (DOT) org>.
GCC: gcc (GCC) 3.3.3 20040412 (Gentoo Linux 3.3.3-r6, ssp-3.3.2-2,
pie-8.7.6)
FS: ReiserFS 3.6
BerkDb: 4.2.52.NC (w/ patches [built against preceeding JDK])
JDK: 1.5.0-rc-b63

mrpoof (AT) hotmail (DOT) com (Dane Foster) wrote in message news:<be935692.0409152055.54b5358b (AT) posting (DOT) google.com>...

If DB_DBT_USERMEM is specified, you need to specify the byte size of
the user-specified buffer .

key.setUserBufferLength(16);

For more information:

http://www.sleepycat.com/docs/java/index.html



Regards,

Ron
Sleepycat Software