Fix hashCode values of aggregations' BytesValues.

This commit removes FilterBytesValues which is very trappy as the default
implementation forwards all method calls to the delegate. So if you do any
non-trivial modification to the terms or to the order of the terms, you need
to remember to override currentValueHash, copyShared, and this is very
error-prone.

FieldDataSource.WithScript.BytesValues and ScriptBytesValues now return correct
hash codes, future bugs here would be catched by the new assertion in
SortedUniqueBytesValues.

This bug was causing performance issues with scripts as all terms were assumed
to have the same hash code.

Close elastic#5004

src/main/java/org/elasticsearch/search/aggregations/support/FieldDataSource.java

@@ -287,31 +287,34 @@ public org.elasticsearch.index.fielddata.BytesValues bytesValues() {
                 return bytesValues;
             }
 
-            static class SortedUniqueBytesValues extends FilterBytesValues {
+            static class SortedUniqueBytesValues extends BytesValues {
 
-                final BytesRef spare;
+                final BytesValues delegate;
                 int[] sortedIds;
                 final BytesRefHash bytes;
                 int numUniqueValues;
                 int pos = Integer.MAX_VALUE;
 
                 public SortedUniqueBytesValues(BytesValues delegate) {
-                    super(delegate);
+                    super(delegate.isMultiValued());
+                    this.delegate = delegate;
                     bytes = new BytesRefHash();
-                    spare = new BytesRef();
                 }
 
                 @Override
                 public int setDocument(int docId) {
-                    final int numValues = super.setDocument(docId);
+                    final int numValues = delegate.setDocument(docId);
                     if (numValues == 0) {
                         sortedIds = null;
                         return 0;
                     }
                     bytes.clear();
                     bytes.reinit();
                     for (int i = 0; i < numValues; ++i) {
-                        bytes.add(super.nextValue(), super.currentValueHash());
+                        final BytesRef next = delegate.nextValue();
+                        final int hash = delegate.currentValueHash();
+                        assert hash == next.hashCode();
+                        bytes.add(next, hash);
                     }
                     numUniqueValues = bytes.size();
                     sortedIds = bytes.sort(BytesRef.getUTF8SortedAsUnicodeComparator());
@@ -321,13 +324,8 @@ public int setDocument(int docId) {
 
                 @Override
                 public BytesRef nextValue() {
-                    bytes.get(sortedIds[pos++], spare);
-                    return spare;
-                }
-
-                @Override
-                public int currentValueHash() {
-                    return spare.hashCode();
+                    bytes.get(sortedIds[pos++], scratch);
+                    return scratch;
                 }
 
                 @Override
@@ -738,13 +736,11 @@ static class BytesValues extends org.elasticsearch.index.fielddata.BytesValues {
 
             private final FieldDataSource source;
             private final SearchScript script;
-            private final BytesRef scratch;
 
             public BytesValues(FieldDataSource source, SearchScript script) {
                 super(true);
                 this.source = source;
                 this.script = script;
-                scratch = new BytesRef();
             }
 
             @Override

src/main/java/org/elasticsearch/search/aggregations/support/bytes/ScriptBytesValues.java

@@ -37,7 +37,6 @@ public class ScriptBytesValues extends BytesValues implements ScriptValues {
 
     private Iterator<?> iter;
     private Object value;
-    private BytesRef scratch = new BytesRef();
 
     public ScriptBytesValues(SearchScript script) {
         super(true); // assume multi-valued