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iterator.go
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iterator.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 gaedatastore
import (
"context"
"fmt"
"github.com/pymjer/cayley/clog"
"github.com/pymjer/cayley/graph"
"github.com/pymjer/cayley/graph/iterator"
"github.com/pymjer/cayley/graph/refs"
"github.com/cayleygraph/quad"
"google.golang.org/appengine/datastore"
)
var _ iterator.Shape = &Iterator{}
const (
bufferSize = 50
)
type Iterator struct {
size int64
dir quad.Direction
qs *QuadStore
t *Token
isAll bool
kind string
}
func (it *Iterator) Iterate() iterator.Scanner {
if it.isAll {
return newAllIteratorNext(it.qs, it.kind)
}
return newIteratorNext(it.qs, it.kind, it.dir, it.t)
}
func (it *Iterator) Lookup() iterator.Index {
if it.isAll {
return newAllIteratorContains(it.qs, it.kind)
}
return newIteratorContains(it.qs, it.kind, it.dir, it.t)
}
func (qs *QuadStore) newIterator(k string, d quad.Direction, val graph.Ref) *Iterator {
t := val.(*Token)
if t == nil {
clog.Errorf("Token == nil")
}
return &Iterator{
dir: d,
qs: qs,
isAll: false,
t: t,
kind: k,
}
}
func (qs *QuadStore) newAllIterator(kind string) *Iterator {
return &Iterator{
qs: qs,
dir: quad.Any,
isAll: true,
kind: kind,
}
}
// No subiterators.
func (it *Iterator) SubIterators() []iterator.Shape {
return nil
}
func (it *Iterator) Sorted() bool { return false }
func (it *Iterator) Optimize(ctx context.Context) (iterator.Shape, bool) { return it, false }
func (it *Iterator) String() string {
name := ""
if it.t != nil {
tn, err := it.qs.NameOf(it.t)
if err != nil {
name = "ERROR(" + err.Error() + ")"
} else {
name = quad.StringOf(tn) + "/" + it.t.Hash
}
}
return fmt.Sprintf("GAE(%s)", name)
}
func (it *Iterator) getSize(ctx context.Context) (refs.Size, error) {
if it.size != 0 {
return refs.Size{
Value: it.size,
Exact: true,
}, nil
}
if !it.isAll {
// The number of references to this node is held in the nodes entity
key := it.qs.createKeyFromToken(it.t)
foundNode := new(NodeEntry)
err := datastore.Get(it.qs.context, key, foundNode)
if err != datastore.ErrNoSuchEntity {
err = nil
}
size := foundNode.Size
it.size = size
return refs.Size{
Value: it.size,
Exact: err == nil,
}, err
}
var size int64
st, err := it.qs.Stats(context.Background(), true)
if it.kind == nodeKind {
size = st.Nodes.Value
} else {
size = st.Quads.Value
}
it.size = size
return refs.Size{
Value: it.size,
Exact: err == nil,
}, err
}
func (it *Iterator) Stats(ctx context.Context) (iterator.Costs, error) {
sz, err := it.getSize(ctx)
// TODO (panamafrancis) calculate costs
return iterator.Costs{
ContainsCost: 1,
NextCost: 5,
Size: sz,
}, err
}
type iteratorNext struct {
dir quad.Direction
qs *QuadStore
name string
isAll bool
kind string
hash string
done bool
buffer []string
offset int
last string
result graph.Ref
err error
}
func newIteratorNext(qs *QuadStore, k string, d quad.Direction, t *Token) *iteratorNext {
if t == nil {
clog.Errorf("Token == nil")
}
if t.Kind != nodeKind {
clog.Errorf("Cannot create an iterator from a non-node value")
return &iteratorNext{done: true}
}
if k != nodeKind && k != quadKind {
clog.Errorf("Cannot create iterator for unknown kind")
return &iteratorNext{done: true}
}
if qs.context == nil {
clog.Errorf("Cannot create iterator without a valid context")
return &iteratorNext{done: true}
}
tn, err := qs.NameOf(t)
if err != nil {
clog.Errorf("Creating iterator token lookup error: %v", err)
return &iteratorNext{done: true, err: err}
}
name := quad.StringOf(tn)
return &iteratorNext{
name: name,
dir: d,
qs: qs,
isAll: false,
kind: k,
hash: t.Hash,
done: false,
}
}
func newAllIteratorNext(qs *QuadStore, kind string) *iteratorNext {
if kind != nodeKind && kind != quadKind {
clog.Errorf("Cannot create iterator for an unknown kind")
return &iteratorNext{done: true}
}
if qs.context == nil {
clog.Errorf("Cannot create iterator without a valid context")
return &iteratorNext{done: true}
}
return &iteratorNext{
qs: qs,
dir: quad.Any,
isAll: true,
kind: kind,
}
}
func (it *iteratorNext) Close() error {
it.buffer = nil
it.offset = 0
it.done = true
it.last = ""
it.result = nil
return nil
}
func (it *iteratorNext) TagResults(dst map[string]graph.Ref) {}
func (it *iteratorNext) NextPath(ctx context.Context) bool {
return false
}
func (it *iteratorNext) Result() graph.Ref {
return it.result
}
func (it *iteratorNext) Next(ctx context.Context) bool {
if it.offset+1 < len(it.buffer) {
it.offset++
it.result = &Token{Kind: it.kind, Hash: it.buffer[it.offset]}
return true
}
if it.done {
return false
}
// Reset buffer and offset
it.offset = 0
it.buffer = make([]string, 0, bufferSize)
// Create query
// TODO (panamafrancis) Keys only query?
q := datastore.NewQuery(it.kind).Limit(bufferSize)
if !it.isAll {
// Filter on the direction {subject,objekt...}
q = q.Filter(it.dir.String()+" =", it.name)
}
// Get last cursor position
cursor, err := datastore.DecodeCursor(it.last)
if err == nil {
q = q.Start(cursor)
}
// Buffer the keys of the next 50 matches
t := q.Run(it.qs.context)
for {
// Quirk of the datastore, you cannot pass a nil value to to Next()
// even if you just want the keys
var k *datastore.Key
skip := false
if it.kind == quadKind {
temp := new(QuadEntry)
k, err = t.Next(temp)
// Skip if quad has been deleted
if len(temp.Added) <= len(temp.Deleted) {
skip = true
}
} else {
temp := new(NodeEntry)
k, err = t.Next(temp)
// Skip if node has been deleted
if temp.Size == 0 {
skip = true
}
}
if err == datastore.Done {
it.done = true
break
}
if err != nil {
clog.Errorf("Error fetching next entry %v", err)
it.err = err
return false
}
if !skip {
it.buffer = append(it.buffer, k.StringID())
}
}
// Save cursor position
cursor, err = t.Cursor()
if err == nil {
it.last = cursor.String()
}
// Protect against bad queries
if it.done && len(it.buffer) == 0 {
clog.Warningf("Query did not return any results")
return false
}
// First result
it.result = &Token{Kind: it.kind, Hash: it.buffer[it.offset]}
return true
}
func (it *iteratorNext) Err() error {
return it.err
}
func (it *iteratorNext) Sorted() bool { return false }
func (it *iteratorNext) String() string {
return fmt.Sprintf("GAE(%s/%s)", it.name, it.hash)
}
type iteratorContains struct {
dir quad.Direction
qs *QuadStore
name string
isAll bool
kind string
hash string
done bool
result graph.Ref
err error
}
func newIteratorContains(qs *QuadStore, k string, d quad.Direction, t *Token) *iteratorContains {
if t == nil {
clog.Errorf("Token == nil")
}
if t.Kind != nodeKind {
clog.Errorf("Cannot create an iterator from a non-node value")
return &iteratorContains{done: true}
}
if k != nodeKind && k != quadKind {
clog.Errorf("Cannot create iterator for unknown kind")
return &iteratorContains{done: true}
}
if qs.context == nil {
clog.Errorf("Cannot create iterator without a valid context")
return &iteratorContains{done: true}
}
tn, err := qs.NameOf(t)
if err != nil {
clog.Errorf("Creating iterator token lookup error: %v", err)
return &iteratorContains{done: true, err: err}
}
name := quad.StringOf(tn)
return &iteratorContains{
name: name,
dir: d,
qs: qs,
isAll: false,
kind: k,
hash: t.Hash,
done: false,
}
}
func newAllIteratorContains(qs *QuadStore, kind string) *iteratorContains {
if kind != nodeKind && kind != quadKind {
clog.Errorf("Cannot create iterator for an unknown kind")
return &iteratorContains{done: true}
}
if qs.context == nil {
clog.Errorf("Cannot create iterator without a valid context")
return &iteratorContains{done: true}
}
return &iteratorContains{
qs: qs,
dir: quad.Any,
isAll: true,
kind: kind,
}
}
func (it *iteratorContains) Close() error {
it.done = true
it.result = nil
return nil
}
func (it *iteratorContains) Contains(ctx context.Context, v graph.Ref) bool {
if it.isAll {
// The result needs to be set, so when contains is called, the result can be retrieved
it.result = v
return true
}
t := v.(*Token)
if t == nil {
clog.Errorf("Could not cast to token")
return false
}
if t.Kind == nodeKind {
clog.Errorf("Contains does not work with node values")
return false
}
// Contains is for when you want to know that an iterator refers to a quad
var offset int
switch it.dir {
case quad.Subject:
offset = 0
case quad.Predicate:
offset = (quad.HashSize * 2)
case quad.Object:
offset = (quad.HashSize * 2) * 2
case quad.Label:
offset = (quad.HashSize * 2) * 3
}
val := t.Hash[offset : offset+(quad.HashSize*2)]
if val == it.hash {
return true
}
return false
}
func (it *iteratorContains) TagResults(dst map[string]graph.Ref) {}
func (it *iteratorContains) NextPath(ctx context.Context) bool {
return false
}
func (it *iteratorContains) Result() graph.Ref {
return it.result
}
func (it *iteratorContains) Err() error {
return it.err
}
func (it *iteratorContains) Sorted() bool { return false }
func (it *iteratorContains) String() string {
return fmt.Sprintf("GAE(%s/%s)", it.name, it.hash)
}