use an array to represent the keys in the uid filter

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

@@ -23,6 +23,7 @@ import org.apache.lucene.index.IndexReader;
 import org.apache.lucene.index.Term;
 import org.apache.lucene.index.TermDocs;
 import org.apache.lucene.util.FixedBitSet;
+import org.elasticsearch.common.lucene.Lucene;
 
 import java.io.IOException;
 import java.util.Iterator;
@@ -77,8 +78,8 @@ public class PublicTermsFilter extends Filter {
         TermDocs td = reader.termDocs();
         try {
             // batch read, in Lucene 4.0 its no longer needed
-            int[] docs = new int[32];
-            int[] freqs = new int[32];
+            int[] docs = new int[Lucene.BATCH_ENUM_DOCS];
+            int[] freqs = new int[Lucene.BATCH_ENUM_DOCS];
             for (Term term : terms) {
                 td.seek(term);
                 int number = td.read(docs, freqs);

src/main/java/org/apache/lucene/search/XTermsFilter.java

@@ -23,6 +23,7 @@ import org.apache.lucene.index.IndexReader;
 import org.apache.lucene.index.Term;
 import org.apache.lucene.index.TermDocs;
 import org.apache.lucene.util.FixedBitSet;
+import org.elasticsearch.common.lucene.Lucene;
 
 import java.io.IOException;
 import java.util.Arrays;
@@ -70,8 +71,8 @@ public class XTermsFilter extends Filter {
         TermDocs td = reader.termDocs();
         try {
             // batch read, in Lucene 4.0 its no longer needed
-            int[] docs = new int[32];
-            int[] freqs = new int[32];
+            int[] docs = new int[Lucene.BATCH_ENUM_DOCS];
+            int[] freqs = new int[Lucene.BATCH_ENUM_DOCS];
             for (Term term : terms) {
                 td.seek(term);
                 int number = td.read(docs, freqs);

src/main/java/org/elasticsearch/common/lucene/Lucene.java

@@ -51,6 +51,8 @@ public class Lucene {
 
     public static ScoreDoc[] EMPTY_SCORE_DOCS = new ScoreDoc[0];
 
+    public static final int BATCH_ENUM_DOCS = 32;
+
     public static Version parseVersion(@Nullable String version, Version defaultVersion, ESLogger logger) {
         if (version == null) {
             return defaultVersion;

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

@@ -25,6 +25,7 @@ import org.apache.lucene.index.TermDocs;
 import org.apache.lucene.search.DocIdSet;
 import org.apache.lucene.search.Filter;
 import org.apache.lucene.util.FixedBitSet;
+import org.elasticsearch.common.lucene.Lucene;
 
 import java.io.IOException;
 
@@ -50,8 +51,8 @@ public class TermFilter extends Filter {
         try {
             td.seek(term);
             // batch read, in Lucene 4.0 its no longer needed
-            int[] docs = new int[32];
-            int[] freqs = new int[32];
+            int[] docs = new int[Lucene.BATCH_ENUM_DOCS];
+            int[] freqs = new int[Lucene.BATCH_ENUM_DOCS];
             int number = td.read(docs, freqs);
             if (number > 0) {
                 result = new FixedBitSet(reader.maxDoc());

src/main/java/org/elasticsearch/index/search/UidFilter.java

@@ -33,22 +33,28 @@ import org.elasticsearch.index.mapper.Uid;
 import org.elasticsearch.index.mapper.internal.UidFieldMapper;
 
 import java.io.IOException;
-import java.util.*;
+import java.util.Arrays;
+import java.util.Collection;
+import java.util.List;
 
 public class UidFilter extends Filter {
 
-    private final Set<Term> uids;
+    private final Term[] uids;
 
     private final BloomCache bloomCache;
 
     public UidFilter(Collection<String> types, List<String> ids, BloomCache bloomCache) {
         this.bloomCache = bloomCache;
-        this.uids = new TreeSet<Term>();
+        this.uids = new Term[types.size() * ids.size()];
+        int i = 0;
         for (String type : types) {
             for (String id : ids) {
-                uids.add(UidFieldMapper.TERM_FACTORY.createTerm(Uid.createUid(type, id)));
+                uids[i++] = UidFieldMapper.TERM_FACTORY.createTerm(Uid.createUid(type, id));
             }
         }
+        if (this.uids.length > 1) {
+            Arrays.sort(this.uids);
+        }
     }
 
     // TODO Optimizations
@@ -69,6 +75,7 @@ public class UidFilter extends Filter {
                     td = reader.termDocs();
                 }
                 td.seek(uid);
+                // no need for batching, its on the UID, there will be only one doc
                 while (td.next()) {
                     if (set == null) {
                         set = new FixedBitSet(reader.maxDoc());
@@ -94,7 +101,14 @@ public class UidFilter extends Filter {
 
     @Override
     public String toString() {
-        return "UidFilter(" + uids + ")";
+        StringBuilder builder = new StringBuilder();
+        for (Term term : uids) {
+            if (builder.length() > 0) {
+                builder.append(' ');
+            }
+            builder.append(term);
+        }
+        return builder.toString();
     }
 
     @Override

src/test/java/org/elasticsearch/test/integration/validate/SimpleValidateQueryTests.java

@@ -116,10 +116,10 @@ public class SimpleValidateQueryTests extends AbstractNodesTests {
         assertThat(response.queryExplanations().get(0).error(), containsString("Failed to parse"));
         assertThat(response.queryExplanations().get(0).explanation(), nullValue());
 
-        assertExplanation(QueryBuilders.queryString("_id:1"), equalTo("ConstantScore(UidFilter([_uid:type1#1]))"));
+        assertExplanation(QueryBuilders.queryString("_id:1"), equalTo("ConstantScore(_uid:type1#1)"));
 
         assertExplanation(QueryBuilders.idsQuery("type1").addIds("1").addIds("2"),
-                equalTo("ConstantScore(UidFilter([_uid:type1#1, _uid:type1#2]))"));
+                equalTo("ConstantScore(_uid:type1#1 _uid:type1#2)"));
 
         assertExplanation(QueryBuilders.queryString("foo"), equalTo("_all:foo"));