forked from cayleygraph/cayley
/
leveldb_triplestore_iterator_optimize.go
53 lines (48 loc) · 1.44 KB
/
leveldb_triplestore_iterator_optimize.go
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// 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 leveldb
import (
"github.com/google/cayley/graph"
)
func (ts *LevelDBTripleStore) OptimizeIterator(it graph.Iterator) (graph.Iterator, bool) {
switch it.Type() {
case "linksto":
return ts.optimizeLinksTo(it.(*graph.LinksToIterator))
}
return it, false
}
func (ts *LevelDBTripleStore) 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
}