46f987ca51
Previously, an incorrectly initialised Delta (omission of Action) would result in an Add operation. Make that detectable and return an error.
101 lines
2.5 KiB
Go
101 lines
2.5 KiB
Go
// Copyright 2014 The Cayley Authors. All rights reserved.
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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package graph
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// Defines the interface for consistent replication of a graph instance.
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//
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// Separate from the backend, this dictates how individual quads get
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// identified and replicated consistently across (potentially) multiple
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// instances. The simplest case is to keep an append-only log of quad
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// changes.
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import (
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"errors"
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"time"
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"github.com/google/cayley/quad"
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)
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type Procedure int8
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// The different types of actions a transaction can do.
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const (
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Add Procedure = +1
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Delete Procedure = -1
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)
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type Delta struct {
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ID PrimaryKey
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Quad quad.Quad
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Action Procedure
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Timestamp time.Time
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}
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type Handle struct {
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QuadStore QuadStore
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QuadWriter QuadWriter
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}
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func (h *Handle) Close() {
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h.QuadStore.Close()
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h.QuadWriter.Close()
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}
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var (
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ErrQuadExists = errors.New("quad exists")
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ErrQuadNotExist = errors.New("quad does not exist")
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)
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type QuadWriter interface {
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// Add a quad to the store.
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AddQuad(quad.Quad) error
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// Add a set of quads to the store, atomically if possible.
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AddQuadSet([]quad.Quad) error
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// Removes a quad matching the given one from the database,
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// if it exists. Does nothing otherwise.
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RemoveQuad(quad.Quad) error
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// Cleans up replication and closes the writing aspect of the database.
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Close() error
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}
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type NewQuadWriterFunc func(QuadStore, Options) (QuadWriter, error)
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var writerRegistry = make(map[string]NewQuadWriterFunc)
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func RegisterWriter(name string, newFunc NewQuadWriterFunc) {
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if _, found := writerRegistry[name]; found {
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panic("already registered QuadWriter " + name)
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}
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writerRegistry[name] = newFunc
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}
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func NewQuadWriter(name string, qs QuadStore, opts Options) (QuadWriter, error) {
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newFunc, hasNew := writerRegistry[name]
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if !hasNew {
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return nil, errors.New("replication: name '" + name + "' is not registered")
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}
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return newFunc(qs, opts)
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}
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func WriterMethods() []string {
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t := make([]string, 0, len(writerRegistry))
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for n := range writerRegistry {
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t = append(t, n)
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}
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return t
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}
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