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quadwriter.go
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/
quadwriter.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 interface for consistent replication of a graph instance.
//
// Separate from the backend, this dictates how individual quads get
// identified and replicated consistently across (potentially) multiple
// instances. The simplest case is to keep an append-only log of quad
// changes.
import (
"errors"
"time"
"github.com/cayleygraph/cayley/quad"
)
type Procedure int8
func (p Procedure) String() string {
switch p {
case +1:
return "add"
case -1:
return "delete"
default:
return "invalid"
}
}
// The different types of actions a transaction can do.
const (
Add Procedure = +1
Delete Procedure = -1
)
type Delta struct {
ID PrimaryKey
Quad quad.Quad
Action Procedure
Timestamp time.Time
}
type Handle struct {
QuadStore
QuadWriter
}
type IgnoreOpts struct {
IgnoreDup, IgnoreMissing bool
}
func (h *Handle) Close() {
h.QuadStore.Close()
h.QuadWriter.Close()
}
var (
ErrQuadExists = errors.New("quad exists")
ErrQuadNotExist = errors.New("quad does not exist")
ErrInvalidAction = errors.New("invalid action")
)
// DeltaError records an error and the delta that caused it.
type DeltaError struct {
Delta Delta
Err error
}
func (e *DeltaError) Error() string {
return e.Delta.Action.String() + " " + e.Delta.Quad.String() + ": " + e.Err.Error()
}
// IsQuadExist returns whether an error is a DeltaError
// with the Err field equal to ErrQuadExists.
func IsQuadExist(err error) bool {
if err == ErrQuadExists {
return true
}
de, ok := err.(*DeltaError)
return ok && de.Err == ErrQuadExists
}
// IsQuadNotExist returns whether an error is a DeltaError
// with the Err field equal to ErrQuadNotExist.
func IsQuadNotExist(err error) bool {
if err == ErrQuadNotExist {
return true
}
de, ok := err.(*DeltaError)
return ok && de.Err == ErrQuadNotExist
}
// IsInvalidAction returns whether an error is a DeltaError
// with the Err field equal to ErrInvalidAction.
func IsInvalidAction(err error) bool {
if err == ErrInvalidAction {
return true
}
de, ok := err.(*DeltaError)
return ok && de.Err == ErrInvalidAction
}
var (
// IgnoreDuplicates specifies whether duplicate quads
// cause an error during loading or are ignored.
IgnoreDuplicates = false
// IgnoreMissing specifies whether missing quads
// cause an error during deletion or are ignored.
IgnoreMissing = false
)
type QuadWriter interface {
// AddQuad adds a quad to the store.
AddQuad(quad.Quad) error
// TODO(barakmich): Deprecate in favor of transaction.
// AddQuadSet adds a set of quads to the store, atomically if possible.
AddQuadSet([]quad.Quad) error
// RemoveQuad removes a quad matching the given one from the database,
// if it exists. Does nothing otherwise.
RemoveQuad(quad.Quad) error
// ApplyTransaction applies a set of quad changes.
ApplyTransaction(*Transaction) error
// RemoveNode removes all quads which have the given node as subject, predicate, object, or label.
RemoveNode(Value) error
// Close cleans up replication and closes the writing aspect of the database.
Close() error
}
type NewQuadWriterFunc func(QuadStore, Options) (QuadWriter, error)
var writerRegistry = make(map[string]NewQuadWriterFunc)
func RegisterWriter(name string, newFunc NewQuadWriterFunc) {
if _, found := writerRegistry[name]; found {
panic("already registered QuadWriter " + name)
}
writerRegistry[name] = newFunc
}
func NewQuadWriter(name string, qs QuadStore, opts Options) (QuadWriter, error) {
newFunc, hasNew := writerRegistry[name]
if !hasNew {
return nil, errors.New("replication: name '" + name + "' is not registered")
}
return newFunc(qs, opts)
}
func WriterMethods() []string {
t := make([]string, 0, len(writerRegistry))
for n := range writerRegistry {
t = append(t, n)
}
return t
}