| /* |
| * 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 java.util.ArrayList; |
| import java.util.HashMap; |
| import java.util.List; |
| import java.util.Map; |
| |
| import org.apache.drill.shaded.guava.com.google.common.base.Preconditions; |
| import org.apache.drill.shaded.guava.com.google.common.collect.ImmutableList; |
| import org.apache.hadoop.hive.metastore.api.FieldSchema; |
| import org.apache.hadoop.hive.metastore.api.Table; |
| |
| /** |
| * The class represents "cache" for partition and table columns. |
| * Used to reduce physical plan for Hive tables. |
| * Only unique partition lists of columns stored in the column lists cache. |
| * Table columns should be stored at index 0. |
| */ |
| public class ColumnListsCache { |
| // contains immutable column lists |
| private final List<List<FieldSchema>> fields; |
| |
| // keys of the map are column lists and values are them positions in list fields |
| private final Map<List<FieldSchema>, Integer> keys; |
| |
| public ColumnListsCache(Table table) { |
| this(); |
| // table columns stored at index 0. |
| addOrGet(table.getSd().getCols()); |
| } |
| |
| public ColumnListsCache() { |
| this.fields = new ArrayList<>(); |
| this.keys = new HashMap<>(); |
| } |
| |
| /** |
| * Checks if column list has been added before and returns position of column list. |
| * If list is unique, adds list to the fields list and returns it position. |
| * Returns -1, if {@param columns} equals null. |
| * |
| * @param columns list of columns |
| * @return index of {@param columns} or -1, if {@param columns} equals null |
| */ |
| public int addOrGet(List<FieldSchema> columns) { |
| if (columns == null) { |
| return -1; |
| } |
| Integer index = keys.get(columns); |
| if (index != null) { |
| return index; |
| } else { |
| index = fields.size(); |
| final List<FieldSchema> immutableList = ImmutableList.copyOf(columns); |
| fields.add(immutableList); |
| keys.put(immutableList, index); |
| return index; |
| } |
| } |
| |
| /** |
| * Returns list of columns at the specified position in fields list, |
| * or null if index is negative or greater than fields list size. |
| * |
| * @param index index of column list to return |
| * @return list of columns at the specified position in fields list |
| * or null if index is negative or greater than fields list size |
| */ |
| public List<FieldSchema> getColumns(int index) { |
| return (index > -1 && index < fields.size()) ? fields.get(index) : null; |
| } |
| |
| /** |
| * Safely retrieves Hive table columns from cache. |
| * |
| * @return list of table columns defined in hive |
| */ |
| public List<FieldSchema> getTableSchemaColumns() { |
| List<FieldSchema> tableSchemaColumns = getColumns(0); |
| Preconditions.checkNotNull(tableSchemaColumns, "Failed to get columns for Hive table from cache."); |
| return tableSchemaColumns; |
| } |
| |
| public List<List<FieldSchema>> getFields() { |
| return new ArrayList<>(fields); |
| } |
| |
| } |