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triplestore.go
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triplestore.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 TripleStore 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
// triple backing store we prefer.
import (
"errors"
"github.com/barakmich/glog"
"github.com/google/cayley/quad"
)
// Defines an opaque "triple store value" type. However the backend wishes to
// implement it, a Value is merely a token to a triple 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 triples, or whatever works best for the
// backing store.
type Value interface{}
type TripleStore interface {
// Add a triple to the store.
AddTriple(*quad.Quad)
// Add a set of triples to the store, atomically if possible.
AddTripleSet([]*quad.Quad)
// Removes a triple matching the given one from the database,
// if it exists. Does nothing otherwise.
RemoveTriple(*quad.Quad)
// Given an opaque token, returns the triple 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.
TripleIterator(quad.Direction, Value) Iterator
// Returns an iterator enumerating all nodes in the graph.
NodesAllIterator() Iterator
// Returns an iterator enumerating all links in the graph.
TriplesAllIterator() Iterator
// Given a node ID, return the opaque token used by the TripleStore
// to represent that id.
ValueOf(string) Value
// Given an opaque token, return the node that it represents.
NameOf(Value) string
// Returns the number of triples currently stored.
Size() int64
// Creates a fixed iterator which can compare Values
FixedIterator() FixedIterator
// Optimize an iterator in the context of the triple store.
// Suppose we have a better index for the passed tree; this
// gives the TripleStore the opportunity to replace it
// with a more efficient iterator.
OptimizeIterator(it Iterator) (Iterator, bool)
// Close the triple store and clean up. (Flush to disk, cleanly
// sever connections, etc)
Close()
// Convenience function for speed. Given a triple token and a direction
// return the node token for that direction. Sometimes, a TripleStore
// can do this without going all the way to the backing store, and
// gives the TripleStore the opportunity to make this optimization.
//
// Iterators will call this. At worst, a valid implementation is
// ts.IdFor(ts.quad.Quad(id).Get(dir))
TripleDirection(id Value, d quad.Direction) Value
}
type Options map[string]interface{}
func (d Options) IntKey(key string) (int, bool) {
if val, ok := d[key]; ok {
switch vv := val.(type) {
case float64:
return int(vv), true
default:
glog.Fatalln("Invalid", key, "parameter type from config.")
}
}
return 0, false
}
func (d Options) StringKey(key string) (string, bool) {
if val, ok := d[key]; ok {
switch vv := val.(type) {
case string:
return vv, true
default:
glog.Fatalln("Invalid", key, "parameter type from config.")
}
}
return "", false
}
var ErrCannotBulkLoad = errors.New("triplestore: cannot bulk load")
type BulkLoader interface {
// BulkLoad loads Quads from a quad.Unmarshaler in bulk to the TripleStore.
// 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) (TripleStore, error)
type InitStoreFunc func(string, Options) error
var storeRegistry = make(map[string]NewStoreFunc)
var storeInitRegistry = make(map[string]InitStoreFunc)
func RegisterTripleStore(name string, newFunc NewStoreFunc, initFunc InitStoreFunc) {
if _, found := storeRegistry[name]; found {
panic("already registered TripleStore " + name)
}
storeRegistry[name] = newFunc
if initFunc != nil {
storeInitRegistry[name] = initFunc
}
}
func NewTripleStore(name, dbpath string, opts Options) (TripleStore, error) {
newFunc, hasNew := storeRegistry[name]
if !hasNew {
return nil, errors.New("triplestore: name '" + name + "' is not registered")
}
return newFunc(dbpath, opts)
}
func InitTripleStore(name, dbpath string, opts Options) error {
initFunc, hasInit := storeInitRegistry[name]
if hasInit {
return initFunc(dbpath, opts)
}
if _, isRegistered := storeRegistry[name]; isRegistered {
return nil
}
return errors.New("triplestore: name '" + name + "' is not registered")
}
func TripleStores() []string {
t := make([]string, 0, len(storeRegistry))
for n := range storeRegistry {
t = append(t, n)
}
return t
}