Github user ravipesala commented on a diff in the pull request:
https://github.com/apache/carbondata/pull/2402#discussion_r197817666
--- Diff:
core/src/main/java/org/apache/carbondata/core/localdictionary/dictionaryholder/MapBasedDictionaryStore.java
---
@@ -0,0 +1,135 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License. You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.apache.carbondata.core.localdictionary.dictionaryholder;
+
+import java.util.Map;
+import java.util.concurrent.ConcurrentHashMap;
+
+import
org.apache.carbondata.core.cache.dictionary.DictionaryByteArrayWrapper;
+import
org.apache.carbondata.core.localdictionary.exception.DictionaryThresholdReachedException;
+
+/**
+ * Map based dictionary holder class, it will use map to hold
+ * the dictionary key and its value
+ */
+public class MapBasedDictionaryStore implements DictionaryStore {
+
+ /**
+ * use to assign dictionary value to new key
+ */
+ private int lastAssignValue;
+
+ /**
+ * to maintain dictionary key value
+ */
+ private final Map<DictionaryByteArrayWrapper, Integer> dictionary;
+
+ /**
+ * maintaining array for reverse lookup
+ * otherwise iterating everytime in map for reverse lookup will be
slowdown the performance
+ * It will only maintain the reference
+ */
+ private byte[][] referenceDictionaryArray;
--- End diff --
Better directly use `DictionaryByteArrayWrapper` array here
---
