add hasSingleArrayBackingStorage

allow for optimization only when there really is a single array, and not when there is a multi dimensional one

src/main/java/org/elasticsearch/index/fielddata/fieldcomparator/BytesRefOrdValComparator.java

@@ -387,12 +387,14 @@ public final class BytesRefOrdValComparator extends FieldComparator<BytesRef> {
         Object ordsStorage = docToOrd.ordinals().getBackingStorage();
         FieldComparator<BytesRef> perSegComp = null;
 
-        if (ordsStorage instanceof byte[]) {
-            perSegComp = new ByteOrdComparator((byte[]) ordsStorage, termsIndex, docBase);
-        } else if (ordsStorage instanceof short[]) {
-            perSegComp = new ShortOrdComparator((short[]) ordsStorage, termsIndex, docBase);
-        } else if (ordsStorage instanceof int[]) {
-            perSegComp = new IntOrdComparator((int[]) ordsStorage, termsIndex, docBase);
+        if (docToOrd.ordinals().hasSingleArrayBackingStorage()) {
+            if (ordsStorage instanceof byte[]) {
+                perSegComp = new ByteOrdComparator((byte[]) ordsStorage, termsIndex, docBase);
+            } else if (ordsStorage instanceof short[]) {
+                perSegComp = new ShortOrdComparator((short[]) ordsStorage, termsIndex, docBase);
+            } else if (ordsStorage instanceof int[]) {
+                perSegComp = new IntOrdComparator((int[]) ordsStorage, termsIndex, docBase);
+            }
         }
         // Don't specialize the long[] case since it's not
         // possible, ie, worse case is MAX_INT-1 docs with

src/main/java/org/elasticsearch/index/fielddata/ordinals/DocIdOrdinals.java

@@ -38,6 +38,11 @@ public class DocIdOrdinals implements Ordinals {
         this.numDocs = numDocs;
     }
 
+    @Override
+    public boolean hasSingleArrayBackingStorage() {
+        return false;
+    }
+
     @Override
     public Object getBackingStorage() {
         return null;

src/main/java/org/elasticsearch/index/fielddata/ordinals/EmptyOrdinals.java

@@ -36,6 +36,11 @@ public class EmptyOrdinals implements Ordinals {
         return 0;
     }
 
+    @Override
+    public boolean hasSingleArrayBackingStorage() {
+        return false;
+    }
+
     @Override
     public Object getBackingStorage() {
         return null;

src/main/java/org/elasticsearch/index/fielddata/ordinals/MultiFlatArrayOrdinals.java

@@ -50,6 +50,11 @@ public class MultiFlatArrayOrdinals implements Ordinals {
         this.numOrds = numOrds;
     }
 
+    @Override
+    public boolean hasSingleArrayBackingStorage() {
+        return false;
+    }
+
     @Override
     public Object getBackingStorage() {
         return ordinals;

src/main/java/org/elasticsearch/index/fielddata/ordinals/Ordinals.java

@@ -19,7 +19,6 @@
 
 package org.elasticsearch.index.fielddata.ordinals;
 
-import org.elasticsearch.common.RamUsage;
 import org.elasticsearch.index.fielddata.util.IntArrayRef;
 
 /**
@@ -27,6 +26,11 @@ import org.elasticsearch.index.fielddata.util.IntArrayRef;
  */
 public interface Ordinals {
 
+    /**
+     * Are the ordinals backed by a single ordinals array?
+     */
+    boolean hasSingleArrayBackingStorage();
+
     /**
      * Returns the backing storage for this ordinals.
      */

src/main/java/org/elasticsearch/index/fielddata/ordinals/SingleArrayOrdinals.java

@@ -37,6 +37,11 @@ public class SingleArrayOrdinals implements Ordinals {
         this.numOrds = numOrds;
     }
 
+    @Override
+    public boolean hasSingleArrayBackingStorage() {
+        return true;
+    }
+
     @Override
     public Object getBackingStorage() {
         return ordinals;

src/main/java/org/elasticsearch/index/fielddata/ordinals/SinglePackedOrdinals.java

@@ -38,6 +38,11 @@ public class SinglePackedOrdinals implements Ordinals {
         this.numOrds = numOrds;
     }
 
+    @Override
+    public boolean hasSingleArrayBackingStorage() {
+        return reader.hasArray();
+    }
+
     @Override
     public Object getBackingStorage() {
         if (reader.hasArray()) {