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indexed_linksto.go
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indexed_linksto.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 mongo
import (
"gopkg.in/mgo.v2"
"gopkg.in/mgo.v2/bson"
"github.com/google/cayley/graph"
"github.com/google/cayley/graph/iterator"
"github.com/google/cayley/quad"
)
var _ graph.Nexter = &LinksTo{}
var linksToType graph.Type
func init() {
linksToType = graph.RegisterIterator("mongo-linksto")
}
// LinksTo is a MongoDB-dependent version of a LinksTo iterator. Like the normal
// LinksTo, it represents a set of links to a set of nodes, represented by its
// subiterator. However, this iterator may often be faster than the generic
// LinksTo, as it can use the secondary indices in Mongo as features within the
// Mongo query, reducing the size of the result set and speeding up iteration.
type LinksTo struct {
uid uint64
collection string
tags graph.Tagger
qs *QuadStore
primaryIt graph.Iterator
dir quad.Direction
nextIt *mgo.Iter
result graph.Value
runstats graph.IteratorStats
lset []graph.Linkage
err error
}
// NewLinksTo constructs a new indexed LinksTo iterator for Mongo around a direction
// and a subiterator of nodes.
func NewLinksTo(qs *QuadStore, it graph.Iterator, collection string, d quad.Direction, lset []graph.Linkage) *LinksTo {
return &LinksTo{
uid: iterator.NextUID(),
qs: qs,
primaryIt: it,
dir: d,
nextIt: nil,
lset: lset,
collection: collection,
}
}
func (it *LinksTo) buildConstraint() bson.M {
constraint := bson.M{}
for _, set := range it.lset {
var s []string
for _, v := range set.Values {
s = append(s, it.qs.NameOf(v))
}
constraint[set.Dir.String()] = bson.M{"$in": s}
if len(s) == 1 {
constraint[set.Dir.String()] = s[0]
}
}
return constraint
}
func (it *LinksTo) buildIteratorFor(d quad.Direction, val graph.Value) *mgo.Iter {
name := it.qs.NameOf(val)
constraint := it.buildConstraint()
constraint[d.String()] = name
return it.qs.db.C(it.collection).Find(constraint).Iter()
}
func (it *LinksTo) UID() uint64 {
return it.uid
}
func (it *LinksTo) Tagger() *graph.Tagger {
return &it.tags
}
// Return the direction under consideration.
func (it *LinksTo) Direction() quad.Direction { return it.dir }
// Tag these results, and our subiterator's results.
func (it *LinksTo) TagResults(dst map[string]graph.Value) {
for _, tag := range it.tags.Tags() {
dst[tag] = it.Result()
}
for tag, value := range it.tags.Fixed() {
dst[tag] = value
}
it.primaryIt.TagResults(dst)
}
// DEPRECATED
func (it *LinksTo) ResultTree() *graph.ResultTree {
tree := graph.NewResultTree(it.Result())
tree.AddSubtree(it.primaryIt.ResultTree())
return tree
}
// Optimize the LinksTo, by replacing it if it can be.
func (it *LinksTo) Optimize() (graph.Iterator, bool) {
return it, false
}
func (it *LinksTo) Next() bool {
var result struct {
ID string `bson:"_id"`
Added []int64 `bson:"Added"`
Deleted []int64 `bson:"Deleted"`
}
graph.NextLogIn(it)
it.runstats.Next += 1
if it.nextIt != nil && it.nextIt.Next(&result) {
it.runstats.ContainsNext += 1
if it.collection == "quads" && len(result.Added) <= len(result.Deleted) {
return it.Next()
}
it.result = result.ID
return graph.NextLogOut(it, it.result, true)
}
if it.nextIt != nil {
// If there's an error in the 'next' iterator, we save it and we're done.
it.err = it.nextIt.Err()
if it.err != nil {
return false
}
}
// Subiterator is empty, get another one
if !graph.Next(it.primaryIt) {
// Possibly save error
it.err = it.primaryIt.Err()
// We're out of nodes in our subiterator, so we're done as well.
return graph.NextLogOut(it, 0, false)
}
if it.nextIt != nil {
it.nextIt.Close()
}
it.nextIt = it.buildIteratorFor(it.dir, it.primaryIt.Result())
// Recurse -- return the first in the next set.
return it.Next()
}
func (it *LinksTo) Err() error {
return it.err
}
func (it *LinksTo) Result() graph.Value {
return it.result
}
func (it *LinksTo) Close() error {
var err error
if it.nextIt != nil {
err = it.nextIt.Close()
}
_err := it.primaryIt.Close()
if _err != nil && err == nil {
err = _err
}
return err
}
func (it *LinksTo) NextPath() bool {
ok := it.primaryIt.NextPath()
if !ok {
it.err = it.primaryIt.Err()
}
return ok
}
func (it *LinksTo) Type() graph.Type {
return linksToType
}
func (it *LinksTo) Clone() graph.Iterator {
m := NewLinksTo(it.qs, it.primaryIt.Clone(), it.collection, it.dir, it.lset)
m.tags.CopyFrom(it)
return m
}
func (it *LinksTo) Contains(val graph.Value) bool {
graph.ContainsLogIn(it, val)
it.runstats.Contains += 1
for _, set := range it.lset {
dval := it.qs.QuadDirection(val, set.Dir)
good := false
for _, val := range set.Values {
if val == dval {
good = true
break
}
}
if !good {
return graph.ContainsLogOut(it, val, false)
}
}
node := it.qs.QuadDirection(val, it.dir)
if it.primaryIt.Contains(node) {
it.result = val
return graph.ContainsLogOut(it, val, true)
}
it.err = it.primaryIt.Err()
return graph.ContainsLogOut(it, val, false)
}
func (it *LinksTo) Describe() graph.Description {
primary := it.primaryIt.Describe()
return graph.Description{
UID: it.UID(),
Type: it.Type(),
Direction: it.dir,
Iterator: &primary,
}
}
func (it *LinksTo) Reset() {
it.primaryIt.Reset()
if it.nextIt != nil {
it.nextIt.Close()
}
it.nextIt = nil
}
// Return a guess as to how big or costly it is to next the iterator.
func (it *LinksTo) Stats() graph.IteratorStats {
subitStats := it.primaryIt.Stats()
// TODO(barakmich): These should really come from the quadstore itself
fanoutFactor := int64(20)
checkConstant := int64(1)
nextConstant := int64(2)
size := fanoutFactor * subitStats.Size
csize, _ := it.qs.getSize(it.collection, it.buildConstraint())
if size > csize {
size = csize
}
return graph.IteratorStats{
NextCost: nextConstant + subitStats.NextCost,
ContainsCost: checkConstant + subitStats.ContainsCost,
Size: size,
Next: it.runstats.Next,
Contains: it.runstats.Contains,
ContainsNext: it.runstats.ContainsNext,
}
}
func (it *LinksTo) Size() (int64, bool) {
return it.Stats().Size, false
}
// Return a list containing only our subiterator.
func (it *LinksTo) SubIterators() []graph.Iterator {
return []graph.Iterator{it.primaryIt}
}