LUCENE-6035: FilteredDocIdSet(Iterator) expose the delegate instance.

git-svn-id: https://svn.apache.org/repos/asf/lucene/dev/trunk@1635596 13f79535-47bb-0310-9956-ffa450edef68

lucene/core/src/java/org/apache/lucene/search/FilteredDocIdSet.java

@@ -52,7 +52,12 @@ public abstract class FilteredDocIdSet extends DocIdSet {
   public FilteredDocIdSet(DocIdSet innerSet) {
     _innerSet = innerSet;
   }
-  
+
+  /** Return the wrapped {@link DocIdSet}. */
+  public DocIdSet getDelegate() {
+    return _innerSet;
+  }
+
   /** This DocIdSet implementation is cacheable if the inner set is cacheable. */
   @Override
   public boolean isCacheable() {

lucene/core/src/java/org/apache/lucene/search/FilteredDocIdSetIterator.java

@@ -41,6 +41,11 @@ public abstract class FilteredDocIdSetIterator extends DocIdSetIterator {
     doc = -1;
   }
 
+  /** Return the wrapped {@link DocIdSetIterator}. */
+  public DocIdSetIterator getDelegate() {
+    return _innerIter;
+  }
+
   /**
    * Validation method to determine whether a docid should be in the result set.
    * @param doc docid to be tested