Re: Help - lo_close: invalid large obj descriptor

Toby,

You need to have autocommit turned off in order to use large objects.
If I add a call to setAutocommit(false) for the connection everything
works fine.

thanks,
--Barry

Toby wrote:
> I've read the docs, I've searched the web.
>
> I'm running PGSql 7.3.4 under Cygwin 1.3.22.1, J2SE 1.4.2, latest stable
> JDBC v3 drivers (pg73jdbc3.jar). This is all running on the same
> machine, a dual AMD with 1GB memory.
>
> 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";
>
> I also tried not using the connection pool, and instead just using the
> straight DriverManager.getConnection() instead, but that fails on the
> lo.write() call too.
>
> I've had large objects working fine on another project (same dev
> machine) a coupla years ago (pg 7.2.x), so I don't think its a case of
> HOW I'm doing it, I suspect there's a bug.
>
> Can someone shed some light?
>
>
> import java.io.File;
> import java.io.FileInputStream;
> import java.sql.Connection;
> import java.sql.DriverManager;
> 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
> //Class.forName("org.postgresql.Driver");
> //conn =
> DriverManager.getConnection("jdbc:postgresql://ash/adserver", "web",
> "web");
> 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);
> //ERROR HAPPENS NEXT
> //ERROR HAPPENS NEXT
> //ERROR HAPPENS NEXT
> 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){}
> }
> }
> }
>
>