/**
* (c) Copyright 2014 WibiData, Inc.
*
* See the NOTICE file distributed with this work for additional
* information regarding copyright ownership.
*
* Licensed 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.kiji.schema.impl.cassandra;
import java.util.HashMap;
import java.util.Map;
import com.datastax.driver.core.PreparedStatement;
import com.datastax.driver.core.Session;
/**
* Caches prepared statement corresponding to Cassandra query strings.
*
*/
public class CassandraStatementCache {
// TODO: this class is a serious memory leak, as well as pretty slow due to the synchronization.
// Replace with a Guava cache with proper expiration.
private final Session mSession;
// TODO (SCHEMA-747): Use a concurrent map, with entries that expire.
private final Map<String, PreparedStatement> mStatementCache;
/**
* Create a new statement cache.
*
* @param session Open session to the Cassandra cluster.
*/
CassandraStatementCache(Session session) {
mSession = session;
mStatementCache = new HashMap<String, PreparedStatement>();
}
/**
* Get a prepared statement for a `String` query.
*
* If we have already cached this query, return the cached value. Otherwise, prepare the
* statement, insert the prepared statement into the cache, and return it.
*
* @param query to turn into a prepared statement.
* @return a prepared statement for the query.
*/
synchronized PreparedStatement getPreparedStatement(String query) {
if (!mStatementCache.containsKey(query)) {
PreparedStatement statement = mSession.prepare(query);
mStatementCache.put(query, statement);
}
return mStatementCache.get(query);
}
}