rename

graph/triplewriter.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 triples get
+// identified and replicated consistently across (potentially) multiple
+// instances. The simplest case is to keep an append-only log of triple
+// changes.
+
+import (
+	"errors"
+	"time"
+)
+
+type Procedure byte
+
+// The different types of actions a transaction can do.
+const (
+	Add Procedure = iota
+	Delete
+)
+
+type Transaction struct {
+	ID        int64
+	Triple    *Triple
+	Action    Procedure
+	Timestamp time.Time
+}
+
+type TripleWriter interface {
+	// Add a triple to the store.
+	AddTriple(*Triple) error
+
+	// Add a set of triples to the store, atomically if possible.
+	AddTripleSet([]*Triple) error
+
+	// Removes a triple matching the given one  from the database,
+	// if it exists. Does nothing otherwise.
+	RemoveTriple(*Triple) error
+}
+
+type NewTripleWriterFunc func(TripleStore, Options) (TripleWriter, error)
+
+var writerRegistry = make(map[string]NewTripleWriterFunc)
+
+func RegisterWriter(name string, newFunc NewTripleWriterFunc) {
+	if _, found := writerRegistry[name]; found {
+		panic("already registered TripleWriter " + name)
+	}
+	writerRegistry[name] = newFunc
+}
+
+func NewTripleWriter(name string, ts TripleStore, opts Options) (TripleWriter, error) {
+	newFunc, hasNew := writerRegistry[name]
+	if !hasNew {
+		return nil, errors.New("replication: name '" + name + "' is not registered")
+	}
+	return newFunc(ts, opts)
+}
+
+func WriterMethods() []string {
+	t := make([]string, 0, len(writerRegistry))
+	for n := range writerRegistry {
+		t = append(t, n)
+	}
+	return t
+}