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/**
* 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 java.util.List;
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";
public static final String READ_ALL_COLUMNS = "hive.io.file.read.all.columns";
public static final String READ_COLUMN_NAMES_CONF_STR = "hive.io.file.readcolumn.names";
private static final String READ_COLUMN_IDS_CONF_STR_DEFAULT = "";
private static final boolean READ_ALL_COLUMNS_DEFAULT = true;
/**
* @deprecated for backwards compatibility with <= 0.12, use setReadAllColumns
*/
@Deprecated
public static void setFullyReadColumns(Configuration conf) {
setReadAllColumns(conf);
}
/**
* @deprecated for backwards compatibility with <= 0.12, use setReadAllColumns
* and appendReadColumns
*/
@Deprecated
public static void setReadColumnIDs(Configuration conf, List ids) {
setReadColumnIDConf(conf, READ_COLUMN_IDS_CONF_STR_DEFAULT);
appendReadColumns(conf, ids);
}
/**
* @deprecated for backwards compatibility with <= 0.12, use appendReadColumns
*/
@Deprecated
public static void appendReadColumnIDs(Configuration conf, List ids) {
appendReadColumns(conf, ids);
}
/**
* Sets the READ_ALL_COLUMNS flag and removes any previously
* set column ids.
*/
public static void setReadAllColumns(Configuration conf) {
conf.setBoolean(READ_ALL_COLUMNS, true);
setReadColumnIDConf(conf, READ_COLUMN_IDS_CONF_STR_DEFAULT);
}
/**
* Returns the READ_ALL_COLUMNS columns flag.
*/
public static boolean isReadAllColumns(Configuration conf) {
return conf.getBoolean(READ_ALL_COLUMNS, READ_ALL_COLUMNS_DEFAULT);
}
/**
* Appends read columns' ids (start from zero). Once a column
* is included in the list, a underlying record reader of a columnar file format
* (e.g. RCFile and ORC) can know what columns are needed.
*/
public static void appendReadColumns(Configuration conf, List ids) {
String id = toReadColumnIDString(ids);
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);
// Set READ_ALL_COLUMNS to false
conf.setBoolean(READ_ALL_COLUMNS, false);
}
public static void appendReadColumns(
Configuration conf, List ids, List names) {
appendReadColumns(conf, ids);
appendReadColumnNames(conf, names);
}
/**
* Returns an array of column ids(start from zero) which is set in the given
* parameter conf.
*/
public static List getReadColumnIDs(Configuration conf) {
String skips = conf.get(READ_COLUMN_IDS_CONF_STR, READ_COLUMN_IDS_CONF_STR_DEFAULT);
String[] list = StringUtils.split(skips);
List result = new ArrayList(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;
}
private static void setReadColumnIDConf(Configuration conf, String id) {
if (id.trim().isEmpty()) {
conf.set(READ_COLUMN_IDS_CONF_STR, READ_COLUMN_IDS_CONF_STR_DEFAULT);
} else {
conf.set(READ_COLUMN_IDS_CONF_STR, id);
}
}
private static void appendReadColumnNames(Configuration conf, List cols) {
String old = conf.get(READ_COLUMN_NAMES_CONF_STR, "");
StringBuilder result = new StringBuilder(old);
boolean first = old.isEmpty();
for(String col: cols) {
if (first) {
first = false;
} else {
result.append(',');
}
result.append(col);
}
conf.set(READ_COLUMN_NAMES_CONF_STR, result.toString());
}
private static String toReadColumnIDString(List ids) {
String id = "";
for (int i = 0; i < ids.size(); i++) {
if (i == 0) {
id = id + ids.get(i);
} else {
id = id + StringUtils.COMMA_STR + ids.get(i);
}
}
return id;
}
private ColumnProjectionUtils() {
// prevent instantiation
}
}
