/**
* 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.mahout.cf.taste.impl.similarity.jdbc;
import org.apache.mahout.cf.taste.common.Refreshable;
import org.apache.mahout.cf.taste.common.TasteException;
import org.apache.mahout.cf.taste.impl.common.jdbc.AbstractJDBCComponent;
import org.apache.mahout.cf.taste.impl.common.jdbc.ResultSetIterator;
import org.apache.mahout.cf.taste.impl.model.jdbc.ConnectionPoolDataSource;
import org.apache.mahout.cf.taste.impl.similarity.GenericItemSimilarity;
import org.apache.mahout.cf.taste.similarity.ItemSimilarity;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import javax.sql.DataSource;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.util.Collection;
import java.util.Iterator;
import java.util.concurrent.locks.ReentrantLock;
/**
* loads all similarities from the database into RAM
*/
abstract class AbstractJDBCInMemoryItemSimilarity extends AbstractJDBCComponent implements ItemSimilarity {
private ItemSimilarity delegate;
private final DataSource dataSource;
private final String getAllItemSimilaritiesSQL;
private final ReentrantLock reloadLock;
private static final Logger log = LoggerFactory.getLogger(AbstractJDBCInMemoryItemSimilarity.class);
AbstractJDBCInMemoryItemSimilarity(DataSource dataSource, String getAllItemSimilaritiesSQL) {
AbstractJDBCComponent.checkNotNullAndLog("getAllItemSimilaritiesSQL", getAllItemSimilaritiesSQL);
if (!(dataSource instanceof ConnectionPoolDataSource)) {
log.warn("You are not using ConnectionPoolDataSource. Make sure your DataSource pools connections "
+ "to the database itself, or database performance will be severely reduced.");
}
this.dataSource = dataSource;
this.getAllItemSimilaritiesSQL = getAllItemSimilaritiesSQL;
this.reloadLock = new ReentrantLock();
reload();
}
@Override
public double itemSimilarity(long itemID1, long itemID2) throws TasteException {
return delegate.itemSimilarity(itemID1, itemID2);
}
@Override
public double[] itemSimilarities(long itemID1, long[] itemID2s) throws TasteException {
return delegate.itemSimilarities(itemID1, itemID2s);
}
@Override
public long[] allSimilarItemIDs(long itemID) throws TasteException {
return delegate.allSimilarItemIDs(itemID);
}
@Override
public void refresh(Collection<Refreshable> alreadyRefreshed) {
log.debug("Reloading...");
reload();
}
protected void reload() {
if (reloadLock.tryLock()) {
try {
delegate = new GenericItemSimilarity(new JDBCSimilaritiesIterable(dataSource, getAllItemSimilaritiesSQL));
} finally {
reloadLock.unlock();
}
}
}
private static class JDBCSimilaritiesIterable implements Iterable<GenericItemSimilarity.ItemItemSimilarity> {
private final DataSource dataSource;
private final String getAllItemSimilaritiesSQL;
private JDBCSimilaritiesIterable(DataSource dataSource, String getAllItemSimilaritiesSQL) {
this.dataSource = dataSource;
this.getAllItemSimilaritiesSQL = getAllItemSimilaritiesSQL;
}
@Override
public Iterator<GenericItemSimilarity.ItemItemSimilarity> iterator() {
try {
return new JDBCSimilaritiesIterator(dataSource, getAllItemSimilaritiesSQL);
} catch (SQLException sqle) {
throw new IllegalStateException(sqle);
}
}
}
private static final class JDBCSimilaritiesIterator
extends ResultSetIterator<GenericItemSimilarity.ItemItemSimilarity> {
private JDBCSimilaritiesIterator(DataSource dataSource, String getAllItemSimilaritiesSQL) throws SQLException {
super(dataSource, getAllItemSimilaritiesSQL);
}
@Override
protected GenericItemSimilarity.ItemItemSimilarity parseElement(ResultSet resultSet) throws SQLException {
return new GenericItemSimilarity.ItemItemSimilarity(resultSet.getLong(1),
resultSet.getLong(2),
resultSet.getDouble(3));
}
}
}