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quadstore_iterator_optimize.go
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/
quadstore_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 (
"context"
"github.com/cayleygraph/cayley/graph"
"github.com/cayleygraph/cayley/graph/iterator"
)
func (qs *QuadStore) OptimizeIterator(it graph.Iterator) (graph.Iterator, bool) {
switch it.Type() {
case graph.LinksTo:
return qs.optimizeLinksTo(it.(*iterator.LinksTo))
}
return it, false
}
func (qs *QuadStore) optimizeLinksTo(it *iterator.LinksTo) (graph.Iterator, bool) {
subs := it.SubIterators()
if len(subs) != 1 {
return it, false
}
ctx := context.TODO()
primary := subs[0]
if primary.Type() == graph.Fixed {
size, _ := primary.Size()
if size == 1 {
if !primary.Next(ctx) {
panic("unexpected size during optimize")
}
val := primary.Result()
newIt := qs.QuadIterator(it.Direction(), val)
nt := newIt.Tagger()
nt.CopyFrom(it)
for _, tag := range primary.Tagger().Tags() {
nt.AddFixed(tag, val)
}
it.Close()
return newIt, true
}
}
return it, false
}