Thread: Help - lo_close: invalid large obj descriptor

I've read the docs, I've searched the web.

I'm running PGSql 7.3.4 under Cygwin 1.3.22.1, using the latest JDBC v3 drivers (jar file).
Accessing the database works fine, but when I try to write to a newly created LargeObject it always fails with

org.postgresql.util.PSQLException - FastPath call returned ERROR:  lo_write: invalid large obj descriptor (0)

The code below illustrates this.

The code is actually going to be used within a Tomcat webapp, but I had to use Jdbc3ConnectionPool since that was the only pool that returned connections that were castable to a PGConnection. I get the same error from inside and outside Tomcat. Thought the error might be related to permissions writing large objects so I tried the following which didn't help.

        GRANT ALL ON "pg_largeobject" TO "web";

So I suspect the problem is related to using a pooled connection. Can someone shed some light?


import java.io.File;
import java.io.FileInputStream;
import java.sql.Connection;
import java.sql.SQLException;

import org.postgresql.PGConnection;
import org.postgresql.jdbc3.Jdbc3ConnectionPool;
import org.postgresql.largeobject.LargeObject;
import org.postgresql.largeobject.LargeObjectManager;

public class TestHarness
{
    public static void main(String[] args)
    {
        LargeObject lo = null;
        Connection conn = null;
        try
        {
            //get a connection that's PGConnection-castable.
            //PoolingDataSource- tried 'n died
            //Jdbc3PoolingDataSource- tried 'n died
            Jdbc3ConnectionPool source = new Jdbc3ConnectionPool();
            source.setServerName("ash");
            source.setDatabaseName("adserver");
            source.setUser("web");
            source.setPassword("web");
            source.setDefaultAutoCommit(false);

            //just to be sure - it always says true so that's good
            conn = source.getConnection();
            System.out.println(conn.getAutoCommit());

            //this only works for connections from Jdbc3ConnectionPool
            PGConnection pgconn = (PGConnection)conn;

            //create the largeobject and prepare to write to it
            LargeObjectManager lom = pgconn.getLargeObjectAPI();
            int oid = lom.create(LargeObjectManager.READ | LargeObjectManager.WRITE);
            lo = lom.open(oid, LargeObjectManager.WRITE);

            //the thing to write
            File file = new File("D:\\downloads\\images\\banner.GIF");
            FileInputStream fis = new FileInputStream(file);

            //prepare a buffer (small enough to force multiple loop iterations
            //so we test it properly)
            byte buff[] = new byte[1024];

            //now write the image
            int bytes_read;
            while ((bytes_read = fis.read(buff, 0, buff.length)) > 0)
            {
                System.out.println("bytes_read=" + bytes_read);
                //this fails with the following error
                //org.postgresql.util.PSQLException - FastPath call returned ERROR:  lo_write: invalid large obj descriptor (0)
                lo.write(buff, 0, bytes_read);
            }

            //clean up
            fis.close();
            System.out.println("done");
        }
        catch (Exception e)
        {
            System.out.println(e.getClass().getName() + " - " + e.getMessage());
        }
        finally
        {
            if (lo != null)    try{lo.close();}catch (SQLException e){}
            if (conn != null) try{conn.close();}catch (SQLException e){}
        }
    }
}