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Posted to issues@ozone.apache.org by "szetszwo (via GitHub)" <gi...@apache.org> on 2023/05/26 16:56:50 UTC
[GitHub] [ozone] szetszwo opened a new pull request, #4782: HDDS-8707. Avoid linear search in DBDefinition implementations.
szetszwo opened a new pull request, #4782:
URL: https://github.com/apache/ozone/pull/4782
## What changes were proposed in this pull request?
DBDefinition declares the following method returning an array.
```java
public DBColumnFamilyDefinition[] getColumnFamilies();
```
It forces the callers to perform a linear search for looking up DBColumnFamilyDefinition by names. The method should return a `Map`.
## What is the link to the Apache JIRA
https://issues.apache.org/jira/browse/HDDS-8707
## How was this patch tested?
By existing unit tests.
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[GitHub] [ozone] szetszwo commented on pull request #4782: HDDS-8707. Avoid linear search in DBDefinition implementations.
Posted by "szetszwo (via GitHub)" <gi...@apache.org>.
szetszwo commented on PR #4782:
URL: https://github.com/apache/ozone/pull/4782#issuecomment-1573026297
When merging this, please add
```
Co-authored-by: Doroszlai, Attila <ad...@apache.org>
```
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[GitHub] [ozone] adoroszlai merged pull request #4782: HDDS-8707. Avoid linear search in DBDefinition implementations.
Posted by "adoroszlai (via GitHub)" <gi...@apache.org>.
adoroszlai merged PR #4782:
URL: https://github.com/apache/ozone/pull/4782
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[GitHub] [ozone] adoroszlai commented on pull request #4782: HDDS-8707. Avoid linear search in DBDefinition implementations.
Posted by "adoroszlai (via GitHub)" <gi...@apache.org>.
adoroszlai commented on PR #4782:
URL: https://github.com/apache/ozone/pull/4782#issuecomment-1573145809
Thanks @szetszwo for updating the patch.
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[GitHub] [ozone] szetszwo commented on a diff in pull request #4782: HDDS-8707. Avoid linear search in DBDefinition implementations.
Posted by "szetszwo (via GitHub)" <gi...@apache.org>.
szetszwo commented on code in PR #4782:
URL: https://github.com/apache/ozone/pull/4782#discussion_r1213811338
##########
hadoop-hdds/framework/src/main/java/org/apache/hadoop/hdds/utils/CollectionUtils.java:
##########
@@ -0,0 +1,87 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements. See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership. The ASF licenses this file
+ * to you 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.apache.hadoop.hdds.utils;
+
+import java.util.ArrayList;
+import java.util.Collection;
+import java.util.Collections;
+import java.util.HashMap;
+import java.util.Iterator;
+import java.util.List;
+import java.util.Map;
+import java.util.NoSuchElementException;
+import java.util.function.Function;
+import java.util.stream.Collectors;
+
+/** Utility methods for Java Collections. */
+public interface CollectionUtils {
+ static <KEY, VALUE> Map<KEY, VALUE> newUnmodifiableMap(
+ List<VALUE> values, Function<VALUE, KEY> getKey,
+ Map<KEY, VALUE> existing) {
+ final Map<KEY, VALUE> map = new HashMap<>(existing);
+ for (VALUE v : values) {
+ final KEY key = getKey.apply(v);
+ final VALUE previous = map.put(key, v);
+ if (previous != null) {
+ throw new IllegalArgumentException("Already exists: " + key
+ + ", previous " + previous.getClass());
+ }
+ }
+ return Collections.unmodifiableMap(map);
+ }
+
+ static <KEY, VALUE> Map<KEY, List<VALUE>> newUnmodifiableMultiMap(
+ List<VALUE> values, Function<VALUE, KEY> getKey) {
+ final Map<KEY, List<VALUE>> map = new HashMap<>();
+ for (VALUE v : values) {
+ final KEY key = getKey.apply(v);
+ map.computeIfAbsent(key, k -> new ArrayList<>()).add(v);
+ }
+ return Collections.unmodifiableMap(map.entrySet().stream()
+ .collect(Collectors.toMap(Map.Entry::getKey,
+ e -> Collections.unmodifiableList(e.getValue()))));
+ }
+
+ static <T> Iterator<T> newIterator(Collection<List<T>> values) {
+ final Iterator<List<T>> listIterator = values.iterator();
+ return new Iterator<T>() {
+ private Iterator<T> i;
+
+ private boolean hasNextItem() {
+ return i != null && i.hasNext();
+ }
+
+ @Override
+ public boolean hasNext() {
+ return listIterator.hasNext() || hasNextItem();
+ }
+
+ @Override
+ public T next() {
+ if (hasNextItem()) {
+ return i.next();
+ }
+ if (listIterator.hasNext()) {
+ i = listIterator.next().iterator();
+ return i.next();
+ }
+ throw new NoSuchElementException();
+ }
Review Comment:
@adoroszlai , good catch! You are right that it won't work if there are empty lists. Thanks for providing the code. Let me try it.
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[GitHub] [ozone] adoroszlai commented on a diff in pull request #4782: HDDS-8707. Avoid linear search in DBDefinition implementations.
Posted by "adoroszlai (via GitHub)" <gi...@apache.org>.
adoroszlai commented on code in PR #4782:
URL: https://github.com/apache/ozone/pull/4782#discussion_r1213435493
##########
hadoop-hdds/framework/src/main/java/org/apache/hadoop/hdds/utils/CollectionUtils.java:
##########
@@ -0,0 +1,87 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements. See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership. The ASF licenses this file
+ * to you 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.apache.hadoop.hdds.utils;
+
+import java.util.ArrayList;
+import java.util.Collection;
+import java.util.Collections;
+import java.util.HashMap;
+import java.util.Iterator;
+import java.util.List;
+import java.util.Map;
+import java.util.NoSuchElementException;
+import java.util.function.Function;
+import java.util.stream.Collectors;
+
+/** Utility methods for Java Collections. */
+public interface CollectionUtils {
+ static <KEY, VALUE> Map<KEY, VALUE> newUnmodifiableMap(
+ List<VALUE> values, Function<VALUE, KEY> getKey,
+ Map<KEY, VALUE> existing) {
+ final Map<KEY, VALUE> map = new HashMap<>(existing);
+ for (VALUE v : values) {
+ final KEY key = getKey.apply(v);
+ final VALUE previous = map.put(key, v);
+ if (previous != null) {
+ throw new IllegalArgumentException("Already exists: " + key
+ + ", previous " + previous.getClass());
+ }
+ }
+ return Collections.unmodifiableMap(map);
+ }
+
+ static <KEY, VALUE> Map<KEY, List<VALUE>> newUnmodifiableMultiMap(
+ List<VALUE> values, Function<VALUE, KEY> getKey) {
+ final Map<KEY, List<VALUE>> map = new HashMap<>();
+ for (VALUE v : values) {
+ final KEY key = getKey.apply(v);
+ map.computeIfAbsent(key, k -> new ArrayList<>()).add(v);
+ }
+ return Collections.unmodifiableMap(map.entrySet().stream()
+ .collect(Collectors.toMap(Map.Entry::getKey,
+ e -> Collections.unmodifiableList(e.getValue()))));
+ }
+
+ static <T> Iterator<T> newIterator(Collection<List<T>> values) {
+ final Iterator<List<T>> listIterator = values.iterator();
+ return new Iterator<T>() {
+ private Iterator<T> i;
+
+ private boolean hasNextItem() {
+ return i != null && i.hasNext();
+ }
+
+ @Override
+ public boolean hasNext() {
+ return listIterator.hasNext() || hasNextItem();
+ }
+
+ @Override
+ public T next() {
+ if (hasNextItem()) {
+ return i.next();
+ }
+ if (listIterator.hasNext()) {
+ i = listIterator.next().iterator();
+ return i.next();
+ }
+ throw new NoSuchElementException();
+ }
Review Comment:
If the current list has no more items, and the next list is empty, then `hasNext()` returns `true`, but `next()` throws `NoSuchElementException`.
I think a safe implementation would be:
```java
private Iterator<T> i = emptyIterator();
private Iterator<T> nextIterator() {
if (i.hasNext()) {
return i;
}
while (listIterator.hasNext()) {
i = listIterator.next().iterator();
if (i.hasNext()) {
return i;
}
}
return emptyIterator();
}
@Override
public boolean hasNext() {
return nextIterator().hasNext();
}
@Override
public T next() {
if (hasNext()) {
return i.next();
}
throw new NoSuchElementException();
}
```
Test:
```java
import org.junit.jupiter.api.Test;
import java.util.ArrayList;
import java.util.List;
import static java.util.Arrays.asList;
import static java.util.Collections.emptyList;
import static org.junit.jupiter.api.Assertions.assertEquals;
class TestCollectionUtils {
@Test
void someEmptyLists() {
List<List<String>> listOfLists = new ArrayList<>();
listOfLists.add(asList("a", "b"));
listOfLists.add(emptyList());
listOfLists.add(emptyList());
listOfLists.add(asList("c", "d"));
listOfLists.add(emptyList());
assertIteration(asList("a", "b", "c", "d"), listOfLists);
}
@Test
void allEmptyLists() {
List<List<String>> listOfLists = new ArrayList<>();
listOfLists.add(emptyList());
listOfLists.add(emptyList());
assertIteration(emptyList(), listOfLists);
}
@Test
void empty() {
assertIteration(emptyList(), emptyList());
}
private static <T> void assertIteration(List<T> expected,
List<List<T>> listOfLists) {
List<T> actual = new ArrayList<>();
CollectionUtils.newIterator(listOfLists).forEachRemaining(actual::add);
assertEquals(expected, actual);
}
}
```
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