Thread

1. lo wrappers - still working on it

   Scott Holmes <sholmes@pacificnet.net> — 2001-07-04T03:56:20Z

   Perhaps someone can point me towards what I'm missing.  I've included my make 
   command, the command for creating a function and the actual code I wrote 
   (derived from the sample code in the docs).  Incidentally, this project is too 
   far along to change to java or any other interface.  I currently am handling 
   the files to be lo's as system files but the request is in to save them as 
   blobs.
   
   This is the result of my make:
   
   gcc -O2 -Wall -Wmissing-prototypes -Wmissing-declarations -fpic 
   -I../../src/interfaces/libpq -I../../src/include   -c -o amslo.o amslo.c
   amslo.c:19: warning: no previous prototype for `ams_loexport'
   gcc -shared -o amslo.so amslo.o
   
   
   This is the result of my trying to create a function:
   
   wcgc_pg=# create function ams_loexport(Oid, char)   
   wcgc_pg-# returns opaque
   wcgc_pg-# as '/usr/local/postgresql-7.1/contrib/WCGC_PG/amslo.so'
   wcgc_pg-# language 'C';
   ERROR:  Load of file /usr/local/postgresql-7.1/contrib/WCGC_PG/amslo.so 
   failed: /usr/local/postgresql-7.1/contrib/WCGC_PG/amslo.so: undefined symbol: 
   PQexec
   wcgc_pg=# 
   
   And finally, this is my attempt at coding the function:
   
   /*---------------------------------------------------------
    * 
    *  amslo.c--
    *   large object handling for wcgc_pg documents
    *
    *
    *---------------------------------------------------------
    */
   #include <stdio.h>
   #include "libpq-fe.h"
   #include "libpq/libpq-fs.h"
   
   #define BUFSIZE		1024
   
   /*
    * ams_loexport * export large object to file
    */
   void ams_loexport(Oid lobjId, char *filename)
   {
     PGconn *conn;
     PGresult *res;
   
     conn = PQsetdb(NULL, NULL, NULL, NULL, "wcgc_pg");
     if (PQstatus(conn) == CONNECTION_BAD)
     {
       fprintf(stderr, "Connection to wcgc_pg failed.\n");
       fprintf(stderr, "%s", PQerrorMessage(conn));
       return;
     }
   
     res = PQexec(conn, "begin");
     PQclear(res);
   
     lo_export(conn, lobjId, filename);
     
     res = PQexec(conn, "end");
     PQclear(res);
     PQfinish(conn);
     return;
   }
   
   
   
   
   
   

2. Re: lo wrappers - still working on it

   Eric G. Miller <egm2@jps.net> — 2001-07-04T04:25:07Z

   On Tue, Jul 03, 2001 at 08:56:20PM -0700, Scott Holmes wrote:
   > Perhaps someone can point me towards what I'm missing.  I've included my make 
   > command, the command for creating a function and the actual code I wrote 
   > (derived from the sample code in the docs).  Incidentally, this project is too 
   > far along to change to java or any other interface.  I currently am handling 
   > the files to be lo's as system files but the request is in to save them as 
   > blobs.
   
   You've written a client-side program, but are trying to use it as a
   server side function.  I don't think that'll work.  You don't want to be
   using libpq for server side functions.  I don't know the Java interface, but 
   it seems you are trying to do what is already available via 
   lo_import/lo_export functions.  Maybe you could explain the interface
   you need a little better.  Is it not possible to use the lo_import() and
   lo_export functions that are already available? (Why they are hidden in
   the Programmer's Guide is beyond me...).
   
   SELECT lo_export (<table>.<column>, '/path/to/file') from <table>;
   INSERT INTO <table> (<column>) VALUES (lo_import ('/path/to/file'));
   
   Someone recently suggested using bytea fields for blobs as well...
   
   -- 
   Eric G. Miller <egm2@jps.net>