1 files changed, 95 insertions, 0 deletions
diff --git a/contrib/storage-hive/core/src/main/java/org/apache/drill/exec/store/hive/HivePartitionHolder.java b/contrib/storage-hive/core/src/main/java/org/apache/drill/exec/store/hive/HivePartitionHolder.java
new file mode 100644
index 000000000..803144e0b
--- /dev/null
+++ b/contrib/storage-hive/core/src/main/java/org/apache/drill/exec/store/hive/HivePartitionHolder.java
@@ -0,0 +1,95 @@
+/*
+ * 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.drill.exec.store.hive;
+
+import com.fasterxml.jackson.annotation.JsonCreator;
+import com.fasterxml.jackson.annotation.JsonProperty;
+
+import java.util.ArrayList;
+import java.util.Collections;
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+
+/**
+ * Helper class that stores partition values per key.
+ * Key to index mapper contains key and index corresponding to partition values position in partition values list.
+ * Since several keys may have that same partition values, such structure is optimized to save memory usage.
+ * Partition values are stored in list of consecutive values.
+ */
+public class HivePartitionHolder {
+
+  private final Map<String, Integer> keyToIndexMapper;
+  private final List<List<String>> partitionValues;
+
+  @JsonCreator
+  public HivePartitionHolder(@JsonProperty("keyToIndexMapper") Map<String, Integer> keyToIndexMapper,
+                             @JsonProperty("partitionValues") List<List<String>> partitionValues) {
+    this.keyToIndexMapper = keyToIndexMapper;
+    this.partitionValues = partitionValues;
+  }
+
+  public HivePartitionHolder() {
+    this.keyToIndexMapper = new HashMap<>();
+    this.partitionValues = new ArrayList<>();
+  }
+
+  @JsonProperty
+  public Map<String, Integer> getKeyToIndexMapper() {
+    return keyToIndexMapper;
+  }
+
+  @JsonProperty
+  public List<List<String>> getPartitionValues() {
+    return partitionValues;
+  }
+
+  /**
+   * Checks if partition values already exist in holder.
+   * If not, adds them to holder and adds key and index corresponding to partition values to mapper.
+   * If partition values exist, adds key and existing partition values index to mapper.
+   *
+   * @param key mapper key
+   * @param values partition values
+   */
+  public void add(String key, List<String> values) {
+    int index = partitionValues.indexOf(values);
+    if (index == -1) {
+      index = partitionValues.size();
+      partitionValues.add(values);
+
+    }
+    keyToIndexMapper.put(key, index);
+  }
+
+  /**
+   * Returns list of partition values stored in holder for the given key.
+   * If there are no corresponding partition values, return empty list.
+   *
+   * @param key mapper key
+   * @return list of partition values
+   */
+  public List<String> get(String key) {
+    Integer index = keyToIndexMapper.get(key);
+    if (index == null) {
+      return Collections.emptyList();
+    }
+    return partitionValues.get(index);
+  }
+
+}