lo_write and lo_import does not work!

Hello,

I have a little trouble using large objects with libpq an postgresql 8.2 in windows xp professional SP2.

I want to save and load large objects from/to database, but its fails.

If i try to use the lo_import() function

#define FILE_IN "d:/question-icon.png"
Oid file_oid = lo_import (conn, FILE_IN);

file_oid always have 0 value, nevertheless the large object has been created in table
pg_largeobject, but has no data.

If i try to create the large object by hand, read the file from disk, and then write the binary data
to the large object, the call to lo_write() always fail (always returns -1):

ifstream is;
is.open (FILE_IN, ios::binary );

// get length of file:
is.seekg (0, ios::end);
length = is.tellg();
is.seekg (0, ios::beg);

// allocate memory:
buffer = new char [length];

// read data as a block:
is.read (buffer,length);
is.close();

/*
* create the large object
*/
lobjId = lo_creat(conn, INV_WRITE);
if (lobjId == 0) {
fprintf(stderr, "no se pudo crear el objeto grande\n");
exit_nicely (conn);
}

lobj_fd = lo_open(conn, lobjId, INV_WRITE);

/*
* Write the content of the file to the large object
*/
tmp = lo_write(conn, lobj_fd, buffer, length);
if (tmp < length) {
fprintf(stderr, "error al escribir el objeto grande: %d bytes escritos\n", tmp);
exit_nicely (conn);
}

In this case, the call to lo_write() does not work, but i can see the large object created in table
pg_largeobject.

Any Idea?

____________________________________________________________________________________
LLama Gratis a cualquier PC del Mundo.
Llamadas a fijos y móviles desde 1 céntimo por minuto.
http://es.voice.yahoo.com

Miguel García escribió:
> Hello,
>
> I have a little trouble using large objects with libpq an postgresql
> 8.2 in windows xp professional SP2.
>
> I want to save and load large objects from/to database, but its fails.
>
> If i try to use the lo_import() function
>
> #define FILE_IN "d:/question-icon.png"
> Oid file_oid = lo_import (conn, FILE_IN);
>
> file_oid always have 0 value, nevertheless the large object has been created in table
> pg_largeobject, but has no data.

I think your problem is that you are not running the commands inside a
transaction. Large object IDs are closed at the end of the transaction
block, which is right after the lo_open unless you're calling BEGIN
first (or are not in autocommit mode, which is the default).

--
Alvaro Herrera http://www.CommandPrompt.com/
PostgreSQL Replication, Consulting, Custom Development, 24x7 support