Use a cursor for fetching data in -d or -D mode, so that pg_dump doesn't

run out of memory with large tables in these modes.  Patch from
Martijn van Oosterhout.

src/bin/pg_dump/pg_dump.c

@@ -22,7 +22,7 @@
  *
  *
  * IDENTIFICATION
- *	  $Header: /cvsroot/pgsql/src/bin/pg_dump/pg_dump.c,v 1.226 2001/08/27 01:09:59 tgl Exp $
+ *	  $Header: /cvsroot/pgsql/src/bin/pg_dump/pg_dump.c,v 1.227 2001/08/27 20:33:07 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -400,20 +400,34 @@ dumpClasses_dumpData(Archive *fout, char *oid, void *dctxv)
 
 	if (fout->remoteVersion >= 70100)
 	{
-		appendPQExpBuffer(q, "SELECT * FROM ONLY %s", fmtId(classname, force_quotes));
+		appendPQExpBuffer(q, "DECLARE _pg_dump_cursor CURSOR FOR SELECT * FROM ONLY %s", fmtId(classname, force_quotes));
 	} else {
-		appendPQExpBuffer(q, "SELECT * FROM %s", fmtId(classname, force_quotes));
+		appendPQExpBuffer(q, "DECLARE _pg_dump_cursor CURSOR FOR SELECT * FROM %s", fmtId(classname, force_quotes));
 	}
 
 	res = PQexec(g_conn, q->data);
 	if (!res ||
-		PQresultStatus(res) != PGRES_TUPLES_OK)
+		PQresultStatus(res) != PGRES_COMMAND_OK)
 	{
 		write_msg(NULL, "dumpClasses(): SQL command failed\n");
 		write_msg(NULL, "Error message from server: %s", PQerrorMessage(g_conn));
 		write_msg(NULL, "The command was: %s\n", q->data);
 		exit_nicely();
 	}
+	
+	do {
+		PQclear(res);
+
+		res = PQexec(g_conn, "FETCH 100 FROM _pg_dump_cursor");
+		if (!res ||
+			PQresultStatus(res) != PGRES_TUPLES_OK)
+		{
+			write_msg(NULL, "dumpClasses(): SQL command failed\n");
+			write_msg(NULL, "Error message from server: %s", PQerrorMessage(g_conn));
+			write_msg(NULL, "The command was: FETCH 100 FROM _pg_dump_cursor\n");
+			exit_nicely();
+		}
+
 		for (tuple = 0; tuple < PQntuples(res); tuple++)
 		{
 			archprintf(fout, "INSERT INTO %s ", fmtId(classname, force_quotes));
@@ -470,7 +484,21 @@ dumpClasses_dumpData(Archive *fout, char *oid, void *dctxv)
 			}
 			archprintf(fout, ");\n");
 		}
+
+	} while( PQntuples(res) > 0 );
+	PQclear(res);
+
+	res = PQexec(g_conn, "CLOSE _pg_dump_cursor");
+	if (!res ||
+		PQresultStatus(res) != PGRES_COMMAND_OK)
+	{
+		write_msg(NULL, "dumpClasses(): SQL command failed\n");
+		write_msg(NULL, "Error message from server: %s", PQerrorMessage(g_conn));
+		write_msg(NULL, "The command was: CLOSE _pg_dump_cursor\n");
+		exit_nicely();
+	}
 	PQclear(res);
+
 	destroyPQExpBuffer(q);
 	return 1;
 }