Re: [GENERAL] Problem with lo_export() and lo_import() from remote machine. - Mailing list pgsql-admin

On 9/11/06, Purusothaman A <purusothaman.a@gmail.com> wrote:
> Hi Marco Bizzarri and Martijn van Oosterhout,
>
>
> Thanks for your valuable reply.
>
> I am trying to execute all query from VC++ through
> CDatabase::ExecuteSQL(sQueryString) function call.
>
> ie, via programming, not by manual entering query statements.
> so, in my situation I can construct a string and pass on to this function to
> execute the query string.
>
> Whatever the string I pass to ExecuteSQL() function, gets executed and I
> cannot get any result retured from the passed query string [like OID -
> 198705, from lo_create()].

I'm not an expert in VC++. I think you should obtain some sort of
ResultSet object. You could then check that.



> Now, can you suggest me how to achieve it?
>
> And one more clarification, what is the value 131072? How can I get this
> vlaue?

This is actually 0x20000 value in decimal. Check large object
interface in postgresql documentation (C API).

> According to PostgreSQL documentation, they gave C Syntax as client side
> function.
>
> Should I use those C API calls?

If you're working from inside C, you can check:

http://www.postgresql.org/docs/8.1/staticI /lo-interfaces.html

Regards
Marco


> :)
> Purusothaman A
>
>
> On 9/11/06, Marco Bizzarri <marco.bizzarri@gmail.com > wrote:
> > I will try to explain it with a sample session: this is for creating
> > and writing a blob.
> >
> > From the psql prompt (> are the commands, the other are the results).
> >
> > > begin ;
> > BEGIN;
> >
> > > SELECT lo_creat(131072) ;
> > lo_creat
> > ----------
> >    198705
> > (1 row)
> > (this is the OID number of the newly created large object).
> >
> > > select  lo_open(198705, 131072) ;
> > lo_open
> > ---------
> >        0
> > (1 row)
> >
> > (this is the file handler which you will use in the operations).
> >
> > > SELECT lowrite(0, 'aaaa');
> > lowrite
> > ---------
> >        4
> > (1 row)
> >
> > (you wrote 4 character in a large object)
> >
> > > select lo_close(0);
> > lo_close
> > ----------
> >         0
> > (1 row)
> >
> > (you closed the file).
> >
> > > commit ;
> > COMMIT
> >
> > In this way, you created a new large object, and stored a string of 4
> > bytes inside of it.
> >
> > Regards
> > Marco
> >
> > On 9/11/06, Purusothaman A < purusothaman.a@gmail.com> wrote:
> > > Thanks Martijn van Oosterhout and Marco Bizzarri.
> > >
> > > But, according to syntax of client side lo_import and lo_export, we
> should
> > > have 2 variable PGconn (for esatablished connection) and lobjld
> (imported
> > > file ID in PostgreSQL).
> > >
> > > I don't know how to do this in SQL statements.
> > >
> > > pls give me sample client side sql statements.
> > >
> > > :)
> > > Purusothaman A
> > >
> > >
> > > On 9/11/06, Martijn van Oosterhout < kleptog@svana.org> wrote:
> > > >
> > > On Mon, Sep 11, 2006 at 03:27:09PM +0530, Purusothaman A wrote:
> > > > Thanks Martijn van Oosterhout,
> > > >
> > > > So, I have to write my own wrapper function upon the functions below.
> > > >   1. Oid lo_import(PGconn *conn, const char *filename);
> > > >   2. int lo_export(PGconn *conn, Oid lobjId, const char *filename);
> > >
> > > Not sure why you need a wrapper (you didn't say which language you were
> > > using) but those functions work exactly like the version you put in the
> > > SQL statements, except the filenames are for the client computer with
> > > client permissions.
> > >
> > > Hope this helps,
> > > --
> > > Martijn van Oosterhout   <kleptog@svana.org>   http://svana.org/kleptog/
> > > > From each according to his ability. To each according to his ability
> to
> > > litigate.
> > >
> > >
> > > -----BEGIN PGP SIGNATURE-----
> > > Version: GnuPG v1.4.1 (GNU/Linux)
> > >
> > >
> iD8DBQFFBTR4IB7bNG8LQkwRAvhPAJ9KHp9DO1EjPqbkGwBdaSaKx5J90wCfQtZ8
> > > ijq1n/SgAlwIiEgDI6zfICg=
> > > =Xk7N
> > > -----END PGP SIGNATURE-----
> > >
> > >
> > >
> > >
> >
> >
> > --
> > Marco Bizzarri
> > http://notenotturne.blogspot.com/
> >
>
>


--
Marco Bizzarri
http://notenotturne.blogspot.com/