optimize term and terms filter that do no match any documents

Author: kimchy

modules/elasticsearch/src/main/java/org/apache/lucene/search/PublicTermsFilter.java

@@ -64,7 +64,7 @@ public boolean equals(Object obj) {
     @Override
     public int hashCode() {
         int hash = 9;
-        for (Iterator<Term> iter = terms.iterator(); iter.hasNext();) {
+        for (Iterator<Term> iter = terms.iterator(); iter.hasNext(); ) {
             Term term = iter.next();
             hash = 31 * hash + term.hashCode();
         }
@@ -73,13 +73,19 @@ public int hashCode() {
 
     @Override
     public DocIdSet getDocIdSet(IndexReader reader) throws IOException {
-        OpenBitSet result = new OpenBitSet(reader.maxDoc());
+        OpenBitSet result = null;
         TermDocs td = reader.termDocs();
         try {
             for (Term term : terms) {
                 td.seek(term);
-                while (td.next()) {
+                if (td.next()) {
+                    if (result == null) {
+                        result = new OpenBitSet(reader.maxDoc());
+                    }
                     result.fastSet(td.doc());
+                    while (td.next()) {
+                        result.fastSet(td.doc());
+                    }
                 }
             }
         } finally {

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

@@ -46,15 +46,18 @@ public Term getTerm() {
     }
 
     @Override public DocIdSet getDocIdSet(IndexReader reader) throws IOException {
-        OpenBitSet result = new OpenBitSet(reader.maxDoc());
+        OpenBitSet result = null;
         TermDocs td = reader.termDocs();
         try {
             td.seek(term);
-            while (td.next()) {
+            if (td.next()) {
+                result = new OpenBitSet(reader.maxDoc());
                 result.fastSet(td.doc());
+                while (td.next()) {
+                    result.fastSet(td.doc());
+                }
             }
-        }
-        finally {
+        } finally {
             td.close();
         }
         return result;