[GitHub] [ozone] adoroszlai commented on a change in pull request #2367: HDDS-5384 OM refreshPipeline should not invoke the expensive OmKeyLocationInfoGroup.getLocationList()

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

adoroszlai commented on a change in pull request #2367:
URL: https://github.com/apache/ozone/pull/2367#discussion_r658609903



##########
File path: hadoop-ozone/common/src/main/java/org/apache/hadoop/ozone/om/helpers/OmKeyLocationInfoGroup.java
##########
@@ -89,17 +90,27 @@ public long getVersion() {
     return version;
   }
 
+  /**
+   * Use this expensive method only when absolutely needed!
+   * It creates a new list so it is not an O(1) operation.
+   * Use getLocationLists() instead.
+   * @return a list of OmKeyLocationInfo
+   */
   public List<OmKeyLocationInfo> getLocationList() {
     return locationVersionMap.values().stream().flatMap(List::stream)
         .collect(Collectors.toList());
   }
 
+  public Collection<List<OmKeyLocationInfo>> getLocationLists() {
+    return locationVersionMap.values();
+  }
+
   public long getLocationListCount() {
     return locationVersionMap.values().stream().mapToLong(List::size).sum();
   }
 
-  public List<OmKeyLocationInfo> getLocationList(Long versionToFetch) {
-    return new ArrayList<>(locationVersionMap.get(versionToFetch));
+  public Collection<OmKeyLocationInfo> getLocationList(Long versionToFetch) {

Review comment:
       According to call hierarchy this is only used in write path, once per key (from `BlockOutputStreamEntryPool#addPreallocateBlocks`).  Based on that, I think we could omit this change now.
   
   Return type does not need to be changed anyway.

##########
File path: hadoop-ozone/ozone-manager/src/main/java/org/apache/hadoop/ozone/om/KeyManagerImpl.java
##########
@@ -745,33 +745,34 @@ protected void refreshPipeline(List<OmKeyInfo> keyList) throws IOException {
     }
 
     Set<Long> containerIDs = new HashSet<>();
-    for (OmKeyInfo keyInfo : keyList) {
-      List<OmKeyLocationInfoGroup> locationInfoGroups =
-          keyInfo.getKeyLocationVersions();
-
-      for (OmKeyLocationInfoGroup key : locationInfoGroups) {
-        for (OmKeyLocationInfo k : key.getLocationList()) {
-          containerIDs.add(k.getContainerID());
-        }
-      }
-    }
+    keyList.forEach(
+        keyInfo -> keyInfo.getKeyLocationVersions().forEach(
+            key -> key.getLocationLists().forEach(
+                OmKeyLocationInfoList -> OmKeyLocationInfoList.forEach(

Review comment:
       Variable name looks like class name.
   
   ```suggestion
                   locationList -> locationList.forEach(
   ```
   
   (Same in the other loop below.)




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