cmccabe commented on a change in pull request #11311:
URL: https://github.com/apache/kafka/pull/11311#discussion_r713235847
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File path: metadata/src/main/java/org/apache/kafka/image/TopicsImage.java
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@@ -92,6 +98,148 @@ public int hashCode() {
return Objects.hash(topicsById, topicsByName);
}
+ /**
+ * Expose a view of this TopicsImage as a map from topic names to IDs.
+ *
+ * Like TopicsImage itself, this map is immutable.
+ */
+ public Map<String, Uuid> topicNameToIdView() {
+ return new TopicNameToIdMap();
+ }
+
+ class TopicNameToIdMap extends AbstractMap<String, Uuid> {
+ private final TopicNameToIdMapEntrySet set = new
TopicNameToIdMapEntrySet();
+
+ @Override
+ public boolean containsKey(Object key) {
+ return topicsByName.containsKey(key);
+ }
+
+ @Override
+ public Uuid get(Object key) {
+ TopicImage image = topicsByName.get(key);
+ if (image == null) return null;
+ return image.id();
+ }
+
+ @Override
+ public Set<Entry<String, Uuid>> entrySet() {
+ return set;
+ }
+ }
+
+ class TopicNameToIdMapEntrySet extends AbstractSet<Entry<String, Uuid>> {
+ @Override
+ public Iterator<Entry<String, Uuid>> iterator() {
+ return new
TopicNameToIdMapEntrySetIterator(topicsByName.entrySet().iterator());
+ }
+
+ @SuppressWarnings("rawtypes")
+ @Override
+ public boolean contains(Object o) {
+ if (!(o instanceof Entry)) return false;
+ Entry other = (Entry) o;
+ TopicImage image = topicsByName.get(other.getKey());
+ if (image == null) return false;
+ return image.id().equals(other.getValue());
+ }
+
+ @Override
+ public int size() {
+ return topicsByName.size();
+ }
+ }
+
+ static class TopicNameToIdMapEntrySetIterator implements
Iterator<Entry<String, Uuid>> {
+ private final Iterator<Entry<String, TopicImage>> iterator;
+
+ TopicNameToIdMapEntrySetIterator(Iterator<Entry<String, TopicImage>>
iterator) {
+ this.iterator = iterator;
+ }
+
+ @Override
+ public boolean hasNext() {
+ return this.iterator.hasNext();
+ }
+
+ @Override
+ public Entry<String, Uuid> next() {
+ Entry<String, TopicImage> entry = iterator.next();
+ return new SimpleImmutableEntry<>(entry.getKey(),
entry.getValue().id());
Review comment:
The existing code literally copies the entire map every time. Copying
the entire map is going to be more expensive than copying just the Entry
elements (although again, this is something we should not be doing, so not
worth optimizing)
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