/**
* 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.metamodel.data;
import java.util.Arrays;
import java.util.List;
import java.util.Map;
import java.util.concurrent.ConcurrentHashMap;
import org.apache.metamodel.query.SelectItem;
import org.apache.metamodel.schema.Column;
/**
* Most common implementation of {@link DataSetHeader}. This implementation is
* 'caching' in the sense that index values of selectitems are cached in a map
* to provide quick access when looking up by {@link SelectItem} or
* {@link Column}.
*/
public final class CachingDataSetHeader extends SimpleDataSetHeader implements DataSetHeader {
private static final long serialVersionUID = 1L;
// map of select item identity codes and indexes in the dataset
private transient Map<Integer, Integer> _selectItemIndexCache;
// map of column identity codes and indexes in the dataset
private transient Map<Integer, Integer> _columnIndexCache;
public CachingDataSetHeader(List<SelectItem> items) {
super(items);
}
public CachingDataSetHeader(SelectItem[] items) {
this(Arrays.asList(items));
}
@Override
public int indexOf(Column column) {
if (column == null) {
return -1;
}
if (_columnIndexCache == null) {
_columnIndexCache = new ConcurrentHashMap<Integer, Integer>(super.size());
}
final int identityCode = System.identityHashCode(column);
Integer index = _columnIndexCache.get(identityCode);
if (index == null) {
index = super.indexOf(column);
if (index != -1) {
_columnIndexCache.put(identityCode, index);
}
}
return index;
}
@Override
public final int indexOf(SelectItem item) {
if (item == null) {
return -1;
}
if (_selectItemIndexCache == null) {
_selectItemIndexCache = new ConcurrentHashMap<Integer, Integer>(super.size());
}
final int identityCode = System.identityHashCode(item);
Integer index = _selectItemIndexCache.get(identityCode);
if (index == null) {
index = super.indexOf(item);
if (index != -1) {
_selectItemIndexCache.put(identityCode, index);
}
}
return index;
}
}