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89 lines
2.4 KiB
89 lines
2.4 KiB
// Copyright 2015 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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import "github.com/google/cayley/quad"
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// Transaction stores a bunch of Deltas to apply atomatically on the database.
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type Transaction struct {
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// Deltas stores the deltas in the right order
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Deltas []Delta
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// deltas stores the deltas in a map to avoid duplications
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deltas map[Delta]struct{}
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}
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// NewTransaction initialize a new transaction.
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func NewTransaction() *Transaction {
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return &Transaction{Deltas: make([]Delta, 0, 10), deltas: make(map[Delta]struct{}, 10)}
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}
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// AddQuad adds a new quad to the transaction if it is not already present in it.
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// If there is a 'remove' delta for that quad, it will remove that delta from
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// the transaction instead of actually addind the quad.
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func (t *Transaction) AddQuad(q quad.Quad) {
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ad, rd := createDeltas(q)
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if _, adExists := t.deltas[ad]; !adExists {
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if _, rdExists := t.deltas[rd]; rdExists {
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t.deleteDelta(rd)
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} else {
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t.addDelta(ad)
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}
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}
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}
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// RemoveQuad adds a quad to remove to the transaction.
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// The quad will be removed from the database if it is not present in the
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// transaction, otherwise it simply remove it from the transaction.
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func (t *Transaction) RemoveQuad(q quad.Quad) {
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ad, rd := createDeltas(q)
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if _, adExists := t.deltas[ad]; adExists {
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t.deleteDelta(ad)
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} else {
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if _, rdExists := t.deltas[rd]; !rdExists {
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t.addDelta(rd)
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}
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}
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}
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func createDeltas(q quad.Quad) (ad, rd Delta) {
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ad = Delta{
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Quad: q,
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Action: Add,
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}
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rd = Delta{
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Quad: q,
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Action: Delete,
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}
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return
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}
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func (t *Transaction) addDelta(d Delta) {
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t.Deltas = append(t.Deltas, d)
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t.deltas[d] = struct{}{}
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}
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func (t *Transaction) deleteDelta(d Delta) {
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delete(t.deltas, d)
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for i, id := range t.Deltas {
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if id == d {
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t.Deltas = append(t.Deltas[:i], t.Deltas[i+1:]...)
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break
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}
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}
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}
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