Fix ancient error in large objects usage example: overwrite() subroutine

was opening with INV_READ flag and then writing.  Prior to 8.1 the backend
did not reject this, but now it does.

doc/src/sgml/lobj.sgml

 <!--
-$PostgreSQL: pgsql/doc/src/sgml/lobj.sgml,v 1.37 2005/06/13 02:26:46 tgl Exp $
+$PostgreSQL: pgsql/doc/src/sgml/lobj.sgml,v 1.38 2006/03/02 21:49:09 tgl Exp $
 -->
 
  <chapter id="largeObjects">
@@ -527,7 +527,7 @@ overwrite(PGconn *conn, Oid lobjId, int start, int len)
     int         nwritten;
     int         i;
 
-    lobj_fd = lo_open(conn, lobjId, INV_READ);
+    lobj_fd = lo_open(conn, lobjId, INV_WRITE);
     if (lobj_fd &lt; 0)
     {
         fprintf(stderr, &quot;can't open large object %d\n&quot;,
@@ -553,7 +553,8 @@ overwrite(PGconn *conn, Oid lobjId, int start, int len)
 }
 
 /*
- * exportFile *    export large object &quot;lobjOid&quot; to file &quot;out_filename&quot;
+ * exportFile
+ *    export large object &quot;lobjOid&quot; to file &quot;out_filename&quot;
  *
  */
 void
@@ -566,7 +567,7 @@ exportFile(PGconn *conn, Oid lobjId, char *filename)
     int         fd;
 
     /*
-     * create an inversion &quot;object&quot;
+     * open the large object
      */
     lobj_fd = lo_open(conn, lobjId, INV_READ);
     if (lobj_fd &lt; 0)
@@ -586,7 +587,7 @@ exportFile(PGconn *conn, Oid lobjId, char *filename)
     }
 
     /*
-     * read in from the Unix file and write to the inversion file
+     * read in from the inversion file and write to the Unix file
      */
     while ((nbytes = lo_read(conn, lobj_fd, buf, BUFSIZE)) &gt; 0)
     {

src/test/examples/testlo.c

@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/test/examples/testlo.c,v 1.25 2004/12/31 22:03:58 pgsql Exp $
+ *	  $PostgreSQL: pgsql/src/test/examples/testlo.c,v 1.26 2006/03/02 21:49:09 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -113,7 +113,7 @@ overwrite(PGconn *conn, Oid lobjId, int start, int len)
 	int			nwritten;
 	int			i;
 
-	lobj_fd = lo_open(conn, lobjId, INV_READ);
+	lobj_fd = lo_open(conn, lobjId, INV_WRITE);
 	if (lobj_fd < 0)
 		fprintf(stderr, "can't open large object %u", lobjId);
 
@@ -156,7 +156,7 @@ exportFile(PGconn *conn, Oid lobjId, char *filename)
 	int			fd;
 
 	/*
-	 * create an inversion "object"
+	 * open the large object
 	 */
 	lobj_fd = lo_open(conn, lobjId, INV_READ);
 	if (lobj_fd < 0)
@@ -173,7 +173,7 @@ exportFile(PGconn *conn, Oid lobjId, char *filename)
 	}
 
 	/*
-	 * read in from the Unix file and write to the inversion file
+	 * read in from the inversion file and write to the Unix file
 	 */
 	while ((nbytes = lo_read(conn, lobj_fd, buf, BUFSIZE)) > 0)
 	{