Attemp to improve hasPendingUpdates()

- Create update list using Stream, so that
  hasPendingUpdates() can short cut on first update found.
- Might improve performance when there is large number of updates in a Tx.

Change-Id: I20820b7212c642315a620d715b5c750e35d31dd0

@@ -20,7 +20,9 @@ import java.util.List;
 import java.util.Map;
 import java.util.Set;
 import java.util.concurrent.CompletableFuture;
-
+import java.util.stream.Collectors;
+import java.util.stream.Stream;
+import org.apache.commons.lang3.tuple.Pair;
 import org.onlab.util.HexString;
 import org.onosproject.store.primitives.MapUpdate;
 import org.onosproject.store.service.AsyncConsistentMap;
@@ -189,41 +191,49 @@ public class DefaultTransactionalMap<K, V> implements TransactionalMap<K, V>, Tr
         return updates().size();
     }
 
-    protected List<MapUpdate<K, V>> updates() {
-        List<MapUpdate<K, V>> updates = Lists.newLinkedList();
-        deleteSet.forEach(key -> {
-            Versioned<V> original = readCache.get(key);
-            if (original != null) {
-                updates.add(MapUpdate.<K, V>newBuilder()
-                        .withMapName(name)
-                        .withType(MapUpdate.Type.REMOVE_IF_VERSION_MATCH)
-                        .withKey(key)
-                        .withCurrentVersion(original.version())
-                        .build());
-            }
-        });
-        writeCache.forEach((key, value) -> {
-            Versioned<V> original = readCache.get(key);
-            if (original == null) {
-                updates.add(MapUpdate.<K, V>newBuilder()
-                        .withMapName(name)
-                        .withType(MapUpdate.Type.PUT_IF_ABSENT)
-                        .withKey(key)
-                        .withValue(value)
-                        .build());
-            } else {
-                updates.add(MapUpdate.<K, V>newBuilder()
-                        .withMapName(name)
-                        .withType(MapUpdate.Type.PUT_IF_VERSION_MATCH)
-                        .withKey(key)
-                        .withCurrentVersion(original.version())
-                        .withValue(value)
-                        .build());
-            }
-        });
-        return updates;
+    @Override
+    public boolean hasPendingUpdates() {
+        return updatesStream().findAny().isPresent();
     }
 
+    protected Stream<MapUpdate<K, V>> updatesStream() {
+        return Stream.concat(
+            // 1st stream: delete ops
+            deleteSet.stream()
+                .map(key -> Pair.of(key, readCache.get(key)))
+                .filter(e -> e.getValue() != null)
+                .map(e -> MapUpdate.<K, V>newBuilder()
+                 .withMapName(name)
+                 .withType(MapUpdate.Type.REMOVE_IF_VERSION_MATCH)
+                 .withKey(e.getKey())
+                 .withCurrentVersion(e.getValue().version())
+                 .build()),
+            // 2nd stream: write ops
+            writeCache.entrySet().stream()
+                    .map(e -> {
+                        Versioned<V> original = readCache.get(e.getKey());
+                        if (original == null) {
+                            return MapUpdate.<K, V>newBuilder()
+                                    .withMapName(name)
+                                    .withType(MapUpdate.Type.PUT_IF_ABSENT)
+                                    .withKey(e.getKey())
+                                    .withValue(e.getValue())
+                                    .build();
+                        } else {
+                            return MapUpdate.<K, V>newBuilder()
+                                    .withMapName(name)
+                                    .withType(MapUpdate.Type.PUT_IF_VERSION_MATCH)
+                                    .withKey(e.getKey())
+                                    .withCurrentVersion(original.version())
+                                    .withValue(e.getValue())
+                                    .build();
+                        }
+                    }));
+    }
+
+    protected List<MapUpdate<K, V>> updates() {
+        return updatesStream().collect(Collectors.toList());
+    }
 
     protected List<MapUpdate<String, byte[]>> toMapUpdates() {
         List<MapUpdate<String, byte[]>> updates = Lists.newLinkedList();