-
Notifications
You must be signed in to change notification settings - Fork 418
/
MergingIterator.java
183 lines (161 loc) · 5.41 KB
/
MergingIterator.java
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
/*
* Copyright (C) 2011 the original author or authors.
* See the notice.md file distributed with this work for additional
* information regarding copyright ownership.
*
* 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 org.iq80.leveldb.util;
import org.iq80.leveldb.impl.InternalKey;
import java.util.Comparator;
import java.util.Iterator;
import java.util.List;
import java.util.Map.Entry;
import java.util.NoSuchElementException;
import java.util.PriorityQueue;
public final class MergingIterator
extends AbstractSeekingIterator<InternalKey, Slice>
{
private final List<? extends InternalIterator> levels;
private final PriorityQueue<ComparableIterator> priorityQueue;
private final Comparator<InternalKey> comparator;
public MergingIterator(List<? extends InternalIterator> levels, Comparator<InternalKey> comparator)
{
this.levels = levels;
this.comparator = comparator;
this.priorityQueue = new PriorityQueue<>(levels.size() + 1);
resetPriorityQueue(comparator);
}
@Override
protected void seekToFirstInternal()
{
for (InternalIterator level : levels) {
level.seekToFirst();
}
resetPriorityQueue(comparator);
}
@Override
protected void seekInternal(InternalKey targetKey)
{
for (InternalIterator level : levels) {
level.seek(targetKey);
}
resetPriorityQueue(comparator);
}
private void resetPriorityQueue(Comparator<InternalKey> comparator)
{
int i = 1;
for (InternalIterator level : levels) {
if (level.hasNext()) {
priorityQueue.add(new ComparableIterator(level, comparator, i++, level.next()));
}
}
}
@Override
protected Entry<InternalKey, Slice> getNextElement()
{
Entry<InternalKey, Slice> result = null;
ComparableIterator nextIterator = priorityQueue.poll();
if (nextIterator != null) {
result = nextIterator.next();
if (nextIterator.hasNext()) {
priorityQueue.add(nextIterator);
}
}
return result;
}
@Override
public String toString()
{
StringBuilder sb = new StringBuilder();
sb.append("MergingIterator");
sb.append("{levels=").append(levels);
sb.append(", comparator=").append(comparator);
sb.append('}');
return sb.toString();
}
private static class ComparableIterator
implements Iterator<Entry<InternalKey, Slice>>, Comparable<ComparableIterator>
{
private final InternalIterator iterator;
private final Comparator<InternalKey> comparator;
private final int ordinal;
private Entry<InternalKey, Slice> nextElement;
private ComparableIterator(InternalIterator iterator, Comparator<InternalKey> comparator, int ordinal, Entry<InternalKey, Slice> nextElement)
{
this.iterator = iterator;
this.comparator = comparator;
this.ordinal = ordinal;
this.nextElement = nextElement;
}
@Override
public boolean hasNext()
{
return nextElement != null;
}
@Override
public Entry<InternalKey, Slice> next()
{
if (nextElement == null) {
throw new NoSuchElementException();
}
Entry<InternalKey, Slice> result = nextElement;
if (iterator.hasNext()) {
nextElement = iterator.next();
}
else {
nextElement = null;
}
return result;
}
@Override
public void remove()
{
throw new UnsupportedOperationException();
}
@Override
public boolean equals(Object o)
{
if (this == o) {
return true;
}
if (o == null || getClass() != o.getClass()) {
return false;
}
ComparableIterator comparableIterator = (ComparableIterator) o;
if (ordinal != comparableIterator.ordinal) {
return false;
}
if (nextElement != null ? !nextElement.equals(comparableIterator.nextElement) : comparableIterator.nextElement != null) {
return false;
}
return true;
}
@Override
public int hashCode()
{
int result = ordinal;
result = 31 * result + (nextElement != null ? nextElement.hashCode() : 0);
return result;
}
@Override
public int compareTo(ComparableIterator that)
{
int result = comparator.compare(this.nextElement.getKey(), that.nextElement.getKey());
if (result == 0) {
result = Integer.compare(this.ordinal, that.ordinal);
}
return result;
}
}
}