Initial Commit

src/graph_mongo/mongo-triplestore-iterator-optimize.go

@@ -0,0 +1,53 @@
+// Copyright 2014 The Cayley Authors. All rights reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package graph_mongo
+
+import (
+	"graph"
+)
+
+func (ts *MongoTripleStore) OptimizeIterator(it graph.Iterator) (graph.Iterator, bool) {
+	switch it.Type() {
+	case "linksto":
+		return ts.optimizeLinksTo(it.(*graph.LinksToIterator))
+
+	}
+	return it, false
+}
+
+func (ts *MongoTripleStore) optimizeLinksTo(it *graph.LinksToIterator) (graph.Iterator, bool) {
+	l := it.GetSubIterators()
+	if l.Len() != 1 {
+		return it, false
+	}
+	primaryIt := l.Front().Value.(graph.Iterator)
+	if primaryIt.Type() == "fixed" {
+		size, _ := primaryIt.Size()
+		if size == 1 {
+			val, ok := primaryIt.Next()
+			if !ok {
+				panic("Sizes lie")
+			}
+			newIt := ts.GetTripleIterator(it.Direction(), val)
+			newIt.CopyTagsFrom(it)
+			for _, tag := range primaryIt.Tags() {
+				newIt.AddFixedTag(tag, val)
+			}
+			it.Close()
+			return newIt, true
+		}
+	}
+	return it, false
+}