/**
* 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.hadoop.hive.serde2;
import java.util.ArrayList;
import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.util.StringUtils;
/**
* ColumnProjectionUtils.
*
*/
public final class ColumnProjectionUtils {
public static final String READ_COLUMN_IDS_CONF_STR = "hive.io.file.readcolumn.ids";
/**
* Sets read columns' ids(start from zero) for RCFile's Reader. Once a column
* is included in the list, RCFile's reader will not skip its value.
*
*/
public static void setReadColumnIDs(Configuration conf, ArrayList<Integer> ids) {
String id = toReadColumnIDString(ids);
setReadColumnIDConf(conf, id);
}
/**
* Sets read columns' ids(start from zero) for RCFile's Reader. Once a column
* is included in the list, RCFile's reader will not skip its value.
*
*/
public static void appendReadColumnIDs(Configuration conf,
ArrayList<Integer> ids) {
String id = toReadColumnIDString(ids);
if (id != null) {
String old = conf.get(READ_COLUMN_IDS_CONF_STR, null);
String newConfStr = id;
if (old != null) {
newConfStr = newConfStr + StringUtils.COMMA_STR + old;
}
setReadColumnIDConf(conf, newConfStr);
}
}
private static void setReadColumnIDConf(Configuration conf, String id) {
if (id == null || id.length() <= 0) {
conf.set(READ_COLUMN_IDS_CONF_STR, "");
return;
}
conf.set(READ_COLUMN_IDS_CONF_STR, id);
}
private static String toReadColumnIDString(ArrayList<Integer> ids) {
String id = null;
if (ids != null) {
for (int i = 0; i < ids.size(); i++) {
if (i == 0) {
id = "" + ids.get(i);
} else {
id = id + StringUtils.COMMA_STR + ids.get(i);
}
}
}
return id;
}
/**
* Returns an array of column ids(start from zero) which is set in the given
* parameter <tt>conf</tt>.
*/
public static ArrayList<Integer> getReadColumnIDs(Configuration conf) {
if (conf == null) {
return new ArrayList<Integer>(0);
}
String skips = conf.get(READ_COLUMN_IDS_CONF_STR, "");
String[] list = StringUtils.split(skips);
ArrayList<Integer> result = new ArrayList<Integer>(list.length);
for (String element : list) {
// it may contain duplicates, remove duplicates
Integer toAdd = Integer.parseInt(element);
if (!result.contains(toAdd)) {
result.add(toAdd);
}
}
return result;
}
/**
* Clears the read column ids set in the conf, and will read all columns.
*/
public static void setFullyReadColumns(Configuration conf) {
conf.set(READ_COLUMN_IDS_CONF_STR, "");
}
private ColumnProjectionUtils() {
// prevent instantiation
}
}