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/
quadstore.go
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/
quadstore.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 graph
// Defines the QuadStore interface. Every backing store must implement at
// least this interface.
//
// Most of these are pretty straightforward. As long as we can surface this
// interface, the rest of the stack will "just work" and we can connect to any
// quad backing store we prefer.
import (
"errors"
"fmt"
"io"
"github.com/google/cayley/quad"
)
// Value defines an opaque "quad store value" type. However the backend wishes
// to implement it, a Value is merely a token to a quad or a node that the
// backing store itself understands, and the base iterators pass around.
//
// For example, in a very traditional, graphd-style graph, these are int64s
// (guids of the primitives). In a very direct sort of graph, these could be
// pointers to structs, or merely quads, or whatever works best for the
// backing store.
//
// These must be comparable, or implement a Keyer interface
// so that they may be stored in maps.
type Value interface {
IsNode() bool
}
// Keyer provides a method for comparing types that are not otherwise comparable.
// The Key method must return a dynamic type that is comparable according to the
// Go language specification. The returned value must be unique for each receiver
// value.
type Keyer interface {
Key() interface{}
}
type key struct {
Val interface{}
Node bool
}
func (k key) IsNode() bool { return k.Node }
// ToKey prepares Value to be stored inside maps, calling Key() if necessary.
func ToKey(v Value) Value {
if k, ok := v.(Keyer); ok {
return key{
Val: k.Key(),
Node: v.IsNode(),
}
}
return v
}
type QuadStore interface {
// The only way in is through building a transaction, which
// is done by a replication strategy.
ApplyDeltas([]Delta, IgnoreOpts) error
// Given an opaque token, returns the quad for that token from the store.
Quad(Value) quad.Quad
// Given a direction and a token, creates an iterator of links which have
// that node token in that directional field.
QuadIterator(quad.Direction, Value) Iterator
// Returns an iterator enumerating all nodes in the graph.
NodesAllIterator() Iterator
// Returns an iterator enumerating all links in the graph.
QuadsAllIterator() Iterator
// Given a node ID, return the opaque token used by the QuadStore
// to represent that id.
ValueOf(quad.Value) Value
// Given an opaque token, return the node that it represents.
NameOf(Value) quad.Value
// Returns the number of quads currently stored.
Size() int64
// The last replicated transaction ID that this quadstore has verified.
Horizon() PrimaryKey
// Creates a fixed iterator which can compare Values
FixedIterator() FixedIterator
// Optimize an iterator in the context of the quad store.
// Suppose we have a better index for the passed tree; this
// gives the QuadStore the opportunity to replace it
// with a more efficient iterator.
OptimizeIterator(it Iterator) (Iterator, bool)
// Close the quad store and clean up. (Flush to disk, cleanly
// sever connections, etc)
Close()
// Convenience function for speed. Given a quad token and a direction
// return the node token for that direction. Sometimes, a QuadStore
// can do this without going all the way to the backing store, and
// gives the QuadStore the opportunity to make this optimization.
//
// Iterators will call this. At worst, a valid implementation is
//
// qs.ValueOf(qs.Quad(id).Get(dir))
//
QuadDirection(id Value, d quad.Direction) Value
// Get the type of QuadStore
//TODO replace this using reflection
Type() string
}
type Options map[string]interface{}
func (d Options) IntKey(key string) (int, bool, error) {
if val, ok := d[key]; ok {
switch vv := val.(type) {
case float64:
return int(vv), true, nil
default:
return 0, false, fmt.Errorf("Invalid %s parameter type from config: %T", key, val)
}
}
return 0, false, nil
}
func (d Options) StringKey(key string) (string, bool, error) {
if val, ok := d[key]; ok {
switch vv := val.(type) {
case string:
return vv, true, nil
default:
return "", false, fmt.Errorf("Invalid %s parameter type from config: %T", key, val)
}
}
return "", false, nil
}
func (d Options) BoolKey(key string) (bool, bool, error) {
if val, ok := d[key]; ok {
switch vv := val.(type) {
case bool:
return vv, true, nil
default:
return false, false, fmt.Errorf("Invalid %s parameter type from config: %T", key, val)
}
}
return false, false, nil
}
var ErrCannotBulkLoad = errors.New("quadstore: cannot bulk load")
var ErrDatabaseExists = errors.New("quadstore: cannot init; database already exists")
type BulkLoader interface {
// BulkLoad loads Quads from a quad.Unmarshaler in bulk to the QuadStore.
// It returns ErrCannotBulkLoad if bulk loading is not possible. For example if
// you cannot load in bulk to a non-empty database, and the db is non-empty.
BulkLoad(quad.Unmarshaler) error
}
type NewStoreFunc func(string, Options) (QuadStore, error)
type InitStoreFunc func(string, Options) error
type UpgradeStoreFunc func(string, Options) error
type NewStoreForRequestFunc func(QuadStore, Options) (QuadStore, error)
type QuadStoreRegistration struct {
NewFunc NewStoreFunc
NewForRequestFunc NewStoreForRequestFunc
UpgradeFunc UpgradeStoreFunc
InitFunc InitStoreFunc
IsPersistent bool
}
var storeRegistry = make(map[string]QuadStoreRegistration)
func RegisterQuadStore(name string, register QuadStoreRegistration) {
if _, found := storeRegistry[name]; found {
panic("already registered QuadStore " + name)
}
storeRegistry[name] = register
}
func NewQuadStore(name, dbpath string, opts Options) (QuadStore, error) {
r, registered := storeRegistry[name]
if !registered {
return nil, errors.New("quadstore: name '" + name + "' is not registered")
}
return r.NewFunc(dbpath, opts)
}
func InitQuadStore(name, dbpath string, opts Options) error {
r, registered := storeRegistry[name]
if registered {
return r.InitFunc(dbpath, opts)
}
return errors.New("quadstore: name '" + name + "' is not registered")
}
func NewQuadStoreForRequest(qs QuadStore, opts Options) (QuadStore, error) {
r, registered := storeRegistry[qs.Type()]
if registered {
return r.NewForRequestFunc(qs, opts)
}
return nil, errors.New("QuadStore does not support Per Request construction, check config")
}
func UpgradeQuadStore(name, dbpath string, opts Options) error {
r, registered := storeRegistry[name]
if registered {
if r.UpgradeFunc != nil {
return r.UpgradeFunc(dbpath, opts)
} else {
return nil
}
}
return errors.New("quadstore: name '" + name + "' is not registered")
}
func IsPersistent(name string) bool {
return storeRegistry[name].IsPersistent
}
func QuadStores() []string {
t := make([]string, 0, len(storeRegistry))
for n := range storeRegistry {
t = append(t, n)
}
return t
}
// NewQuadReader returns a quad.Reader, that will read all quads from the store.
func NewQuadReader(qs QuadStore) quad.ReadCloser {
return NewQuadReaderWithIterator(qs, qs.QuadsAllIterator())
}
// NewQuadReaderWithIterator returns a quad.Reader that reads quads from a given iterator.
//
// Closing a reader will also close an iterator.
func NewQuadReaderWithIterator(qs QuadStore, it Iterator) quad.ReadCloser {
nexter, ok := it.(Nexter)
if !ok {
panic("iterator is not a Nexter")
}
return &iteratorReader{qs: qs, it: nexter}
}
type iteratorReader struct {
qs QuadStore
it Nexter
}
func (r *iteratorReader) ReadQuad() (quad.Quad, error) {
if r.it.Next() {
return r.qs.Quad(r.it.Result()), nil
}
if err := r.it.Err(); err != nil {
return quad.Quad{}, err
}
return quad.Quad{}, io.EOF
}
func (r *iteratorReader) Close() error {
return r.it.Close()
}