As proposed,

following is the patch to libpq's large object interface that
    removes the requirement to  include  fmgr.h  into  fe-lobj.c.
    The  large object interface now ask's the backend to tell the
    OID's of all the required functions in pg_proc.

From: wieck@sapserv.debis.de (Jan Wieck)

src/interfaces/libpq/fe-connect.c

@@ -7,7 +7,7 @@
  *
  *
  * IDENTIFICATION
- *    $Header: /cvsroot/pgsql/src/interfaces/libpq/fe-connect.c,v 1.17 1996/11/10 03:06:36 momjian Exp $
+ *    $Header: /cvsroot/pgsql/src/interfaces/libpq/fe-connect.c,v 1.18 1996/11/11 12:16:54 scrappy Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -192,6 +192,7 @@ PQconnectdb(const char *conninfo)
     conn->Pfdebug = NULL;
     conn->port = NULL;
     conn->notifyList = DLNewList();
+    conn->lobjfuncs = NULL;
 
     conn->pghost    = strdup(conninfo_getval("host"));
     conn->pgport    = strdup(conninfo_getval("port"));
@@ -299,6 +300,7 @@ PQsetdb(const char *pghost, const char* pgport, const char* pgoptions, const cha
     conn->Pfdebug = NULL;
     conn->port = NULL;
     conn->notifyList = DLNewList();
+    conn->lobjfuncs = NULL;
     
     if (!pghost || pghost[0] == '\0') {
       if (!(tmp = getenv("PGHOST"))) {
@@ -519,6 +521,7 @@ freePGconn(PGconn *conn)
   if (conn->dbName) free(conn->dbName);
   if (conn->pguser) free(conn->pguser);
   if (conn->notifyList) DLFreeList(conn->notifyList);
+  if (conn->lobjfuncs) free(conn->lobjfuncs);
   free(conn);
 }
 

src/interfaces/libpq/fe-lobj.c

@@ -7,7 +7,7 @@
  *
  *
  * IDENTIFICATION
- *    $Header: /cvsroot/pgsql/src/interfaces/libpq/fe-lobj.c,v 1.3 1996/11/08 06:02:28 momjian Exp $
+ *    $Header: /cvsroot/pgsql/src/interfaces/libpq/fe-lobj.c,v 1.4 1996/11/11 12:16:56 scrappy Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -18,7 +18,6 @@
 #include <sys/types.h>
 #include "postgres.h"
 #include "libpq-fe.h"
-#include "fmgr.h" 
 #include "libpq/libpq-fs.h"
 
 #ifndef MAXPATHLEN
@@ -27,6 +26,8 @@
 
 #define LO_BUFSIZE        1024
 
+static int lo_initialize(PGconn *conn);
+
 /*
  * lo_open
  *    opens an existing large object
@@ -50,7 +51,13 @@ lo_open(PGconn* conn, Oid lobjId, int mode)
     argv[1].len = 4;
     argv[1].u.integer = mode;
 
-    res = PQfn(conn, F_LO_OPEN,&fd,&result_len,1,argv,2); 
+    if(conn->lobjfuncs == (PGlobjfuncs *)NULL) {
+        if(lo_initialize(conn) < 0) {
+	    return -1;
+	}
+    }
+    
+    res = PQfn(conn, conn->lobjfuncs->fn_lo_open,&fd,&result_len,1,argv,2); 
     if (PQresultStatus(res) == PGRES_COMMAND_OK) {
 	PQclear(res);
 
@@ -78,10 +85,17 @@ lo_close(PGconn *conn, int fd)
     int retval;
     int result_len;
 
+    if(conn->lobjfuncs == (PGlobjfuncs *)NULL) {
+        if(lo_initialize(conn) < 0) {
+	    return -1;
+	}
+    }
+    
     argv[0].isint = 1;
     argv[0].len = 4;
     argv[0].u.integer = fd;
-    res = PQfn(conn, F_LO_CLOSE,&retval,&result_len,1,argv,1);
+    res = PQfn(conn, conn->lobjfuncs->fn_lo_close,
+    		&retval,&result_len,1,argv,1);
     if (PQresultStatus(res) == PGRES_COMMAND_OK) {
 	PQclear(res);
 	return retval;
@@ -104,6 +118,12 @@ lo_read(PGconn *conn, int fd, char *buf, int len)
     PGresult *res;
     int result_len;
 
+    if(conn->lobjfuncs == (PGlobjfuncs *)NULL) {
+        if(lo_initialize(conn) < 0) {
+	    return -1;
+	}
+    }
+    
     argv[0].isint = 1;
     argv[0].len = 4;
     argv[0].u.integer = fd;
@@ -112,7 +132,8 @@ lo_read(PGconn *conn, int fd, char *buf, int len)
     argv[1].len = 4;
     argv[1].u.integer = len;
 
-    res = PQfn(conn, F_LOREAD,(int*)buf,&result_len,0,argv,2);
+    res = PQfn(conn, conn->lobjfuncs->fn_lo_read,
+    		(int*)buf,&result_len,0,argv,2);
     if (PQresultStatus(res) == PGRES_COMMAND_OK) {
 	PQclear(res);
 	return result_len;
@@ -133,6 +154,12 @@ lo_write(PGconn *conn, int fd, char *buf, int len)
     int result_len;
     int retval;
 
+    if(conn->lobjfuncs == (PGlobjfuncs *)NULL) {
+        if(lo_initialize(conn) < 0) {
+	    return -1;
+	}
+    }
+    
     if (len <= 0)
 	return 0;
 
@@ -144,7 +171,8 @@ lo_write(PGconn *conn, int fd, char *buf, int len)
     argv[1].len = len;
     argv[1].u.ptr = (int*)buf;
 
-    res = PQfn(conn, F_LOWRITE,&retval,&result_len,1,argv,2);
+    res = PQfn(conn, conn->lobjfuncs->fn_lo_write,
+    		&retval,&result_len,1,argv,2);
     if (PQresultStatus(res) == PGRES_COMMAND_OK) {
 	PQclear(res);
 	return retval;
@@ -167,6 +195,12 @@ lo_lseek(PGconn *conn, int fd, int offset, int whence)
     int retval; 
     int result_len;
     
+    if(conn->lobjfuncs == (PGlobjfuncs *)NULL) {
+        if(lo_initialize(conn) < 0) {
+	    return -1;
+	}
+    }
+    
     argv[0].isint = 1;
     argv[0].len = 4;
     argv[0].u.integer = fd;
@@ -179,7 +213,8 @@ lo_lseek(PGconn *conn, int fd, int offset, int whence)
     argv[2].len = 4;
     argv[2].u.integer = whence;
 
-    res = PQfn(conn, F_LO_LSEEK,&retval,&result_len,1,argv,3);
+    res = PQfn(conn, conn->lobjfuncs->fn_lo_lseek,
+    		&retval,&result_len,1,argv,3);
     if (PQresultStatus(res) == PGRES_COMMAND_OK) {
 	PQclear(res);
 	return retval;
@@ -204,10 +239,17 @@ lo_creat(PGconn *conn, int mode)
     int retval;
     int result_len;
 
+    if(conn->lobjfuncs == (PGlobjfuncs *)NULL) {
+        if(lo_initialize(conn) < 0) {
+	    return -1;
+	}
+    }
+    
     argv[0].isint = 1;
     argv[0].len = 4;
     argv[0].u.integer = mode;
-    res  = PQfn(conn, F_LO_CREAT,&retval,&result_len,1,argv,1);
+    res  = PQfn(conn, conn->lobjfuncs->fn_lo_creat,
+    		&retval,&result_len,1,argv,1);
     if (PQresultStatus(res) == PGRES_COMMAND_OK) {
 	PQclear(res);
 	return (Oid)retval;
@@ -230,11 +272,18 @@ lo_tell(PGconn *conn, int fd)
     PGresult *res;
     int result_len;
 
+    if(conn->lobjfuncs == (PGlobjfuncs *)NULL) {
+        if(lo_initialize(conn) < 0) {
+	    return -1;
+	}
+    }
+    
     argv[0].isint = 1;
     argv[0].len = 4;
     argv[0].u.integer = fd;
 
-    res = PQfn(conn, F_LO_TELL,&retval,&result_len,1,argv,1);
+    res = PQfn(conn, conn->lobjfuncs->fn_lo_tell,
+    		&retval,&result_len,1,argv,1);
     if (PQresultStatus(res) == PGRES_COMMAND_OK) {
 	PQclear(res);
 	return retval;
@@ -256,11 +305,18 @@ lo_unlink(PGconn *conn, Oid lobjId)
     int result_len;
     int retval;
 
+    if(conn->lobjfuncs == (PGlobjfuncs *)NULL) {
+        if(lo_initialize(conn) < 0) {
+	    return -1;
+	}
+    }
+    
     argv[0].isint = 1;
     argv[0].len = 4;
     argv[0].u.integer = lobjId;
 
-    res = PQfn(conn, F_LO_UNLINK,&retval,&result_len,1,argv,1);
+    res = PQfn(conn, conn->lobjfuncs->fn_lo_unlink,
+    		&retval,&result_len,1,argv,1);
     if (PQresultStatus(res) == PGRES_COMMAND_OK) {
 	PQclear(res);
 	return retval;
@@ -380,3 +436,157 @@ lo_export(PGconn *conn, Oid lobjId, char *filename)
 
     return 1;
 }
+
+
+/* ----------------
+ * lo_initialize
+ *
+ * Initialize the large object interface for an existing connection.
+ * We ask the backend about the functions OID's in pg_proc for all
+ * functions that are required for large object operations.
+ * ----------------
+ */
+static int lo_initialize(PGconn *conn)
+{
+    PGresult	*res;
+    PGlobjfuncs *lobjfuncs;
+    int		n;
+    char	*fname;
+    Oid		foid;
+
+    /* ----------------
+     * Allocate the structure to hold the functions OID's
+     * ----------------
+     */
+    lobjfuncs = (PGlobjfuncs *)malloc(sizeof(PGlobjfuncs));
+    if (lobjfuncs == (PGlobjfuncs *)NULL) {
+        strcpy(conn->errorMessage, 
+	    "FATAL: malloc() failed in lo_initialize()\n");
+        return -1;
+    }
+    memset((char *)lobjfuncs, 0, sizeof(PGlobjfuncs));
+
+    /* ----------------
+     * Execute the query to get all the functions at once
+     * ----------------
+     */
+    res = PQexec(conn, "select proname, oid from pg_proc	\
+    		where proname = 'lo_open'	\
+		   or proname = 'lo_close'	\
+		   or proname = 'lo_creat'	\
+		   or proname = 'lo_unlink'	\
+		   or proname = 'lo_lseek'	\
+		   or proname = 'lo_tell'	\
+		   or proname = 'LOread'	\
+		   or proname = 'LOwrite'");
+    if (res == (PGresult *)NULL) {
+	free(lobjfuncs);
+        return -1;
+    }
+
+    if (res->resultStatus != PGRES_TUPLES_OK) {
+        free(lobjfuncs);
+	PQclear(res);
+	strcpy(conn->errorMessage,
+	    "ERROR: SELECT didn't return data in lo_initialize()\n");
+	return -1;
+    }
+
+    /* ----------------
+     * Examine the result and put the OID's into the struct
+     * ----------------
+     */
+    for(n = 0; n < PQntuples(res); n++) {
+        fname = PQgetvalue(res, n, 0);
+	foid  = (Oid)atoi(PQgetvalue(res, n, 1));
+	if(!strcmp(fname, "lo_open")) {
+	    lobjfuncs->fn_lo_open = foid;
+	} else
+	if(!strcmp(fname, "lo_close")) {
+	    lobjfuncs->fn_lo_close = foid;
+	} else
+	if(!strcmp(fname, "lo_creat")) {
+	    lobjfuncs->fn_lo_creat = foid;
+	} else
+	if(!strcmp(fname, "lo_unlink")) {
+	    lobjfuncs->fn_lo_unlink = foid;
+	} else
+	if(!strcmp(fname, "lo_lseek")) {
+	    lobjfuncs->fn_lo_lseek = foid;
+	} else
+	if(!strcmp(fname, "lo_tell")) {
+	    lobjfuncs->fn_lo_tell = foid;
+	} else
+	if(!strcmp(fname, "LOread")) {
+	    lobjfuncs->fn_lo_read = foid;
+	} else
+	if(!strcmp(fname, "LOwrite")) {
+	    lobjfuncs->fn_lo_write = foid;
+	}
+    }
+
+    PQclear(res);
+
+    /* ----------------
+     * Finally check that we really got all large object
+     * interface functions.
+     * ----------------
+     */
+    if(lobjfuncs->fn_lo_open == 0) {
+        strcpy(conn->errorMessage,
+	    "ERROR: Cannot determine OID for function lo_open\n");
+	free(lobjfuncs);
+	return -1;
+    }
+    if(lobjfuncs->fn_lo_close == 0) {
+        strcpy(conn->errorMessage,
+	    "ERROR: Cannot determine OID for function lo_close\n");
+	free(lobjfuncs);
+	return -1;
+    }
+    if(lobjfuncs->fn_lo_creat == 0) {
+        strcpy(conn->errorMessage,
+	    "ERROR: Cannot determine OID for function lo_creat\n");
+	free(lobjfuncs);
+	return -1;
+    }
+    if(lobjfuncs->fn_lo_unlink == 0) {
+        strcpy(conn->errorMessage,
+	    "ERROR: Cannot determine OID for function lo_unlink\n");
+	free(lobjfuncs);
+	return -1;
+    }
+    if(lobjfuncs->fn_lo_lseek == 0) {
+        strcpy(conn->errorMessage,
+	    "ERROR: Cannot determine OID for function lo_lseek\n");
+	free(lobjfuncs);
+	return -1;
+    }
+    if(lobjfuncs->fn_lo_tell == 0) {
+        strcpy(conn->errorMessage,
+	    "ERROR: Cannot determine OID for function lo_tell\n");
+	free(lobjfuncs);
+	return -1;
+    }
+    if(lobjfuncs->fn_lo_read == 0) {
+        strcpy(conn->errorMessage,
+	    "ERROR: Cannot determine OID for function LOread\n");
+	free(lobjfuncs);
+	return -1;
+    }
+    if(lobjfuncs->fn_lo_write == 0) {
+        strcpy(conn->errorMessage,
+	    "ERROR: Cannot determine OID for function LOwrite\n");
+	free(lobjfuncs);
+	return -1;
+    }
+
+    /* ----------------
+     * Put the structure into the connection control
+     * ----------------
+     */
+    conn->lobjfuncs = lobjfuncs;
+    return 0;
+}
+
+

src/interfaces/libpq/libpq-fe.h

@@ -6,7 +6,7 @@
  *
  * Copyright (c) 1994, Regents of the University of California
  *
- * $Id: libpq-fe.h,v 1.11 1996/11/10 03:06:38 momjian Exp $
+ * $Id: libpq-fe.h,v 1.12 1996/11/11 12:16:57 scrappy Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -96,6 +96,17 @@ typedef struct pgNotify {
     int be_pid;			/* process id of backend */
 } PGnotify;
 
+typedef struct pgLobjfuncs {
+    Oid fn_lo_open;		/* OID of backend function lo_open	*/
+    Oid fn_lo_close;		/* OID of backend function lo_close	*/
+    Oid fn_lo_creat;		/* OID of backend function lo_creat	*/
+    Oid fn_lo_unlink;		/* OID of backend function lo_unlink	*/
+    Oid fn_lo_lseek;		/* OID of backend function lo_lseek	*/
+    Oid fn_lo_tell;		/* OID of backend function lo_tell	*/
+    Oid fn_lo_read;		/* OID of backend function LOread	*/
+    Oid fn_lo_write;		/* OID of backend function LOwrite	*/
+} PGlobjfuncs;
+
 /* PGconn encapsulates a connection to the backend */
 typedef struct pg_conn{
   char *pghost; /* the machine on which the server is running */
@@ -113,6 +124,7 @@ typedef struct pg_conn{
   int asyncNotifyWaiting;
   Dllist* notifyList;
   char *pguser;  /* Postgres username of user who is connected */
+  PGlobjfuncs *lobjfuncs; /* Backend function OID's for large object access */
 } PGconn;
 
 #define CMDSTATUS_LEN 40