Ability to skip Incremental Index during query using query context

This PR adds adds the ability to skip incremental index when querying
results from realtime nodes. default behaviour is to include
incrementalIndex in queries.

review comment

server/src/main/java/io/druid/segment/realtime/plumber/RealtimePlumber.java

@@ -49,6 +49,7 @@
 import io.druid.data.input.Committer;
 import io.druid.data.input.InputRow;
 import io.druid.query.MetricsEmittingQueryRunner;
+import io.druid.query.NoopQueryRunner;
 import io.druid.query.Query;
 import io.druid.query.QueryRunner;
 import io.druid.query.QueryRunnerFactory;
@@ -132,6 +133,8 @@ public class RealtimePlumber implements Plumber
 
   private static final String COMMIT_METADATA_KEY = "%commitMetadata%";
   private static final String COMMIT_METADATA_TIMESTAMP_KEY = "%commitMetadataTimestamp%";
+  private static final String SKIP_INCREMENTAL_SEGMENT = "skipIncrementalSegment";
+
 
   public RealtimePlumber(
       DataSchema schema,
@@ -255,6 +258,7 @@ private Sink getSink(long timestamp)
   @Override
   public <T> QueryRunner<T> getQueryRunner(final Query<T> query)
   {
+    final boolean skipIncrementalSegment = query.getContextValue(SKIP_INCREMENTAL_SEGMENT, false);
     final QueryRunnerFactory<T, Query<T>> factory = conglomerate.findFactory(query);
     final QueryToolChest<T, Query<T>> toolchest = factory.getToolchest();
 
@@ -322,6 +326,10 @@ public QueryRunner<T> apply(FireHydrant input)
                                               return new ReportTimelineMissingSegmentQueryRunner<T>(descriptor);
                                             }
 
+                                            if (skipIncrementalSegment && !input.hasSwapped()) {
+                                              return new NoopQueryRunner<T>();
+                                            }
+
                                             // Prevent the underlying segment from closing when its being iterated
                                             final Closeable closeable = input.getSegment().increment();
                                             try {