Query DSL: Bool filter does not take should clauses properly into account, closes elastic#1511.

Author: kimchy

modules/elasticsearch/src/main/java/org/elasticsearch/common/lucene/search/XBooleanFilter.java

@@ -89,10 +89,6 @@ public DocIdSet getDocIdSet(IndexReader reader) throws IOException {
 
         if (notFilters != null) {
             for (int i = 0; i < notFilters.size(); i++) {
-                if (res == null) {
-                    res = new FixedBitSet(reader.maxDoc());
-                    res.set(0, reader.maxDoc()); // NOTE: may set bits on deleted docs
-                }
                 final DocIdSet disi = getDISI(notFilters, i, reader);
                 if (disi != null) {
                     DocSets.andNot(res, disi);
@@ -106,12 +102,7 @@ public DocIdSet getDocIdSet(IndexReader reader) throws IOException {
                 if (disi == null) {
                     return null;
                 }
-                if (res == null) {
-                    res = new FixedBitSet(reader.maxDoc());
-                    DocSets.or(res, disi);
-                } else {
-                    DocSets.and(res, disi);
-                }
+                DocSets.and(res, disi);
             }
         }