reduce memory usage for end points

do not copy entire segments when not needed,
reduces memory pressure on the coordinator when no. of segments is
large enough.

server/src/main/java/io/druid/server/coordinator/DruidCoordinator.java

@@ -422,7 +422,7 @@ public class DruidCoordinator
     }
   }
 
-  public Set<DataSegment> getAvailableDataSegments()
+  public Set<DataSegment> getOrderedAvailableDataSegments()
   {
     Set<DataSegment> availableSegments = Sets.newTreeSet(Comparators.inverse(DataSegment.bucketMonthComparator()));
 
@@ -452,6 +452,23 @@ public class DruidCoordinator
     return availableSegments;
   }
 
+  public Iterable<DataSegment> getAvailableDataSegments()
+  {
+    return Iterables.concat(
+        Iterables.transform(
+            databaseSegmentManager.getInventory(),
+            new Function<DruidDataSource, Iterable<DataSegment>>()
+            {
+              @Override
+              public Iterable<DataSegment> apply(DruidDataSource input)
+              {
+                return input.getSegments();
+              }
+            }
+        )
+    );
+  }
+
   @LifecycleStart
   public void start()
   {

server/src/main/java/io/druid/server/coordinator/helper/DruidCoordinatorSegmentInfoLoader.java

@@ -41,7 +41,7 @@ public class DruidCoordinatorSegmentInfoLoader implements DruidCoordinatorHelper
   public DruidCoordinatorRuntimeParams run(DruidCoordinatorRuntimeParams params)
   {
     // Display info about all available segments
-    final Set<DataSegment> availableSegments = coordinator.getAvailableDataSegments();
+    final Set<DataSegment> availableSegments = coordinator.getOrderedAvailableDataSegments();
     if (log.isDebugEnabled()) {
       log.debug("Available DataSegments");
       for (DataSegment dataSegment : availableSegments) {