[GitHub] [hadoop-ozone] adoroszlai commented on a change in pull request #1381: HDDS-4201. Improve the performance of OmKeyLocationInfoGroup

[GitBox <gi...@apache.org>]

adoroszlai commented on a change in pull request #1381:
URL: https://github.com/apache/hadoop-ozone/pull/1381#discussion_r483005141



##########
File path: hadoop-ozone/common/src/main/java/org/apache/hadoop/ozone/om/helpers/OmKeyLocationInfoGroup.java
##########
@@ -36,8 +36,13 @@
   public OmKeyLocationInfoGroup(long version,
                                 List<OmKeyLocationInfo> locations) {
     this.version = version;
-    this.locationVersionMap = locations.stream()
-        .collect(Collectors.groupingBy(OmKeyLocationInfo::getCreateVersion));
+    locationVersionMap = new HashMap<>();
+    for (OmKeyLocationInfo info : locations) {
+      if (!locationVersionMap.containsKey(info.getCreateVersion())) {
+        locationVersionMap.put(info.getCreateVersion(), new ArrayList<>());
+      }
+      locationVersionMap.get(info.getCreateVersion()).add(info);

Review comment:
       I think we can avoid two map lookups (and long autoboxing) by using `computeIfAbsent`:
   
   ```suggestion
         locationVersionMap
             .computeIfAbsent(info.getCreateVersion(), v -> new ArrayList<>())
             .add(info);
   ```




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