From d8764cbdb168fc2a9f2cafc70478733dc5d7637d Mon Sep 17 00:00:00 2001
From: arnobrinkman <arnobrinkman@users.sourceforge.net>
Date: Wed, 4 May 2005 08:56:14 +0000
Subject: [PATCH] Fix problem with distributing sort to deeper RSE, query
 example: SELECT   RDB$RELATION_NAME FROM   (SELECT FIRST 10 * FROM
 RDB$RELATIONS ORDER BY RDB$RELATION_NAME DESC) ORDER BY   RDB$RELATION_NAME

---
 src/jrd/opt.cpp | 13 +++++++++++++
 1 file changed, 13 insertions(+)

diff --git a/src/jrd/opt.cpp b/src/jrd/opt.cpp
index fef28f3f19..a04b3df472 100644
--- a/src/jrd/opt.cpp
+++ b/src/jrd/opt.cpp
@@ -1679,6 +1679,16 @@ static void check_sorts(RecordSelExpr* rse)
 			while (node) {
 				if (node->nod_type == nod_rse) {
 					new_rse = (RecordSelExpr*) node;
+
+					// AB: Don't distribute the sort when a FIRST/SKIP is supllied, 
+					// because that will effect the behaviour from the deeper RSE.
+					if (new_rse->rse_first || new_rse->rse_skip) {
+						node = NULL;
+						break;
+					}
+
+					// Walk trough the relations of the RSE and see if a
+					// matching stream can be found.
 					if (new_rse->rse_jointype == blr_inner) {
 						if (new_rse->rse_count == 1) {
 							node = new_rse->rse_relation[0];
@@ -1691,12 +1701,14 @@ static void check_sorts(RecordSelExpr* rse)
 									((USHORT)(IPTR)subNode->nod_arg[e_rel_stream]) == sort_stream && 
 									new_rse != rse) 
 								{
+									// We have found the correct stream
 									sortStreamFound = true;
 									break;
 								}
 
 							}
 							if (sortStreamFound) {
+								// Set the sort to the found stream and clear the original sort
 								new_rse->rse_sorted = sort;
 								sort = rse->rse_sorted = NULL;
 							}
@@ -1715,6 +1727,7 @@ static void check_sorts(RecordSelExpr* rse)
 						((USHORT)(IPTR)node->nod_arg[e_rel_stream]) == sort_stream && 
 						new_rse && new_rse != rse) 
 					{
+						// We have found the correct stream, thus apply the sort here
 						new_rse->rse_sorted = sort;
 						sort = rse->rse_sorted = NULL;
 					}