diff --git a/src/backend/tcop/postgres.c b/src/backend/tcop/postgres.c
index a5484d9..08f1788 100644
--- a/src/backend/tcop/postgres.c
+++ b/src/backend/tcop/postgres.c
@@ -943,10 +943,6 @@ exec_simple_query(const char *query_string)
 
 		plantree_list = pg_plan_queries(querytree_list, 0, NULL);
 
-		/* Done with the snapshot used for parsing/planning */
-		if (snapshot_set)
-			PopActiveSnapshot();
-
 		/* If we got a cancel signal in analysis or planning, quit */
 		CHECK_FOR_INTERRUPTS();
 
@@ -971,9 +967,19 @@ exec_simple_query(const char *query_string)
 						  NULL);
 
 		/*
-		 * Start the portal.  No parameters here.
+		 * Start the portal.
+		 * 
+		 * If we took a snapshot for parsing/planning, the portal may be
+		 * able to reuse it for the execution phase.  Currently, this will only
+		 * happen in PORTAL_ONE_SELECT mode.  But even if PortalStart doesn't
+		 * end up being able to do this, keeping the parse/plan snapshot around
+		 * until after we start the portal doesn't cost much.
 		 */
-		PortalStart(portal, NULL, false);
+		PortalStart(portal, NULL, snapshot_set);
+
+		/* Done with the snapshot used for parsing/planning */
+		if (snapshot_set)
+			PopActiveSnapshot();
 
 		/*
 		 * Select the appropriate output format: text unless we are doing a
@@ -1696,14 +1702,18 @@ exec_bind_message(StringInfo input_message)
 					  cplan->stmt_list,
 					  cplan);
 
-	/* Done with the snapshot used for parameter I/O and parsing/planning */
-	if (snapshot_set)
-		PopActiveSnapshot();
-
 	/*
 	 * And we're ready to start portal execution.
+	 *
+	 * If we took a snapshot for parsing/planning, we'll try to reuse it
+	 * for query execution (currently, reuse will only occur if
+	 * PORTAL_ONE_SELECT mode is chosen).
 	 */
-	PortalStart(portal, params, false);
+	PortalStart(portal, params, snapshot_set);
+
+	/* Done with the snapshot used for parameter I/O and parsing/planning */
+	if (snapshot_set)
+		PopActiveSnapshot();
 
 	/*
 	 * Apply the result format requests to the portal.
diff --git a/src/backend/tcop/pquery.c b/src/backend/tcop/pquery.c
index c41272b..75c7dee 100644
--- a/src/backend/tcop/pquery.c
+++ b/src/backend/tcop/pquery.c
@@ -446,10 +446,11 @@ FetchStatementTargetList(Node *stmt)
  * the query, they must be passed in here (caller is responsible for
  * giving them appropriate lifetime).
  *
- * The caller can optionally pass a snapshot to be used; pass InvalidSnapshot
- * for the normal behavior of setting a new snapshot.  This parameter is
- * presently ignored for non-PORTAL_ONE_SELECT portals (it's only intended
- * to be used for cursors).
+ * The use_active_snapshot parameter is currently used only for
+ * PORTAL_ONE_SELECT portals.  If it is true, the active snapshot will
+ * be used when starting up the executor; if false, a new snapshot will
+ * be taken.  This is used both for cursors and to avoid taking an entirely
+ * new snapshot when it isn't necessary.
  *
  * On return, portal is ready to accept PortalRun() calls, and the result
  * tupdesc (if any) is known.