jacques-n commented on a change in pull request #11063:
URL: https://github.com/apache/arrow/pull/11063#discussion_r700629594
##########
File path:
java/memory/memory-core/src/main/java/org/apache/arrow/util/Collections2.java
##########
@@ -46,23 +45,55 @@ private Collections2() {}
* Converts the iterable into a new {@link List}.
*/
public static <T> List<T> toList(Iterable<T> iterable) {
- return StreamSupport.stream(iterable.spliterator(),
false).collect(Collectors.toList());
+ if (iterable instanceof Collection<?>) {
+ // If iterable is a collection, take advantage of it for a more
efficient copy
+ return new ArrayList<T>((Collection<T>) iterable);
+ }
+ return toList(iterable.iterator());
}
+ /**
+ * Converts the iterable into a new immutable {@link List}.
+ */
+ public static <T> List<T> toImmutableList(Iterable<T> iterable) {
+ return Collections.unmodifiableList(toList(iterable));
+ }
+
+
/** Copies the elements of <code>map</code> to a new unmodifiable map. */
public static <K, V> Map<K, V> immutableMapCopy(Map<K, V> map) {
- Map<K, V> newMap = new HashMap<>();
- newMap.putAll(map);
- return java.util.Collections.unmodifiableMap(newMap);
+ return Collections.unmodifiableMap(new HashMap<>(map));
}
/** Copies the elements of list to a new unmodifiable list. */
public static <V> List<V> immutableListCopy(List<V> list) {
- return
Collections.unmodifiableList(list.stream().collect(Collectors.toList()));
+ return Collections.unmodifiableList(new ArrayList<>(list));
}
/** Copies the values to a new unmodifiable list. */
public static <V> List<V> asImmutableList(V...values) {
return Collections.unmodifiableList(Arrays.asList(values));
}
+
+ /**
+ * Creates a human readable string from the remaining elements in iterator.
+ *
+ * The output should be similar to {@code Arrays#toString(Object[])}
+ */
+ public static String toString(Iterator<?> iterator) {
+ if (!iterator.hasNext()) {
Review comment:
Isn't there a better stream-y way to do this with join?
##########
File path:
java/vector/src/main/java/org/apache/arrow/vector/types/pojo/Schema.java
##########
@@ -97,7 +97,7 @@ public static Schema
convertSchema(org.apache.arrow.flatbuf.Schema schema) {
String value = kv.value();
metadata.put(key == null ? "" : key, value == null ? "" : value);
}
- return new Schema(Collections2.immutableListCopy(fields),
Collections2.immutableMapCopy(metadata));
+ return new Schema(true, Collections.unmodifiableList(fields),
Collections.unmodifiableMap(metadata));
Review comment:
You're skipping the defensive copy here? Seems like a change in behavior.
##########
File path:
java/vector/src/main/java/org/apache/arrow/vector/types/pojo/FieldType.java
##########
@@ -68,11 +69,9 @@ public FieldType(boolean nullable, ArrowType type,
DictionaryEncoding dictionary
extensionMetadata.put(ExtensionType.EXTENSION_METADATA_KEY_NAME,
((ExtensionType) type).extensionName());
extensionMetadata.put(ExtensionType.EXTENSION_METADATA_KEY_METADATA,
((ExtensionType) type).serialize());
if (metadata != null) {
- for (Map.Entry<String, String> entry : metadata.entrySet()) {
- extensionMetadata.put(entry.getKey(), entry.getValue());
- }
+ extensionMetadata.putAll(metadata);
}
- this.metadata = Collections2.immutableMapCopy(extensionMetadata);
+ this.metadata = Collections.unmodifiableMap(extensionMetadata);
Review comment:
You're removing the copy here. Is this safe?
##########
File path:
java/memory/memory-core/src/main/java/org/apache/arrow/util/Collections2.java
##########
@@ -46,23 +45,55 @@ private Collections2() {}
* Converts the iterable into a new {@link List}.
*/
public static <T> List<T> toList(Iterable<T> iterable) {
- return StreamSupport.stream(iterable.spliterator(),
false).collect(Collectors.toList());
+ if (iterable instanceof Collection<?>) {
+ // If iterable is a collection, take advantage of it for a more
efficient copy
+ return new ArrayList<T>((Collection<T>) iterable);
+ }
+ return toList(iterable.iterator());
}
+ /**
+ * Converts the iterable into a new immutable {@link List}.
+ */
+ public static <T> List<T> toImmutableList(Iterable<T> iterable) {
+ return Collections.unmodifiableList(toList(iterable));
Review comment:
Can we specialize this so it avoids a copy if the existing set is
unmodifiable with a safe backing. Same with the unmodifiable map below. Seems
like you could then keep the defensive copies you've removed below in Schema
and FieldType
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