org.apache.lucene.store.jdbc.lock.PhantomReadLock Maven / Gradle / Ivy
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/*
* Copyright 2004-2009 the original author or authors.
*
* 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.apache.lucene.store.jdbc.lock;
import java.io.IOException;
import java.sql.PreparedStatement;
import java.sql.Types;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.apache.lucene.store.Lock;
import org.apache.lucene.store.jdbc.JdbcDirectory;
import org.apache.lucene.store.jdbc.support.JdbcTemplate;
/**
* A lock based on phantom reads and table level locking. For most database and most transaction
* isolation levels this lock is suffecient.
*
*
The existance of the lock in the database, marks it as being locked.
*
*
The benefits of using this lock is the ability to release it.
*
* @author kimchy
*/
public class PhantomReadLock extends Lock implements JdbcLock {
private static final Log log = LogFactory.getLog(PhantomReadLock.class);
private JdbcDirectory jdbcDirectory;
private String name;
public void configure(JdbcDirectory jdbcDirectory, String name) throws IOException {
this.jdbcDirectory = jdbcDirectory;
this.name = name;
}
public void initializeDatabase(JdbcDirectory jdbcDirectory) {
// do nothing
}
public boolean obtain() {
try {
if (jdbcDirectory.getDialect().useExistsBeforeInsertLock()) {
// there are databases where the fact that an exception was thrown
// invalidates the connection. So first we check if it exists, and
// then insert it.
if (jdbcDirectory.fileExists(name)) {
return false;
}
}
jdbcDirectory.getJdbcTemplate().executeUpdate(jdbcDirectory.getTable().sqlInsert(),
new JdbcTemplate.PrepateStatementAwareCallback() {
public void fillPrepareStatement(PreparedStatement ps) throws Exception {
ps.setFetchSize(1);
ps.setString(1, name);
ps.setNull(2, Types.BLOB);
ps.setLong(3, 0);
ps.setBoolean(4, false);
}
});
} catch (Exception e) {
if (log.isTraceEnabled()) {
log.trace("Obtain Lock exception (might be valid) [" + e.getMessage() + "]");
}
return false;
}
return true;
}
public void release() {
try {
jdbcDirectory.getJdbcTemplate().executeUpdate(jdbcDirectory.getTable().sqlDeleteByName(),
new JdbcTemplate.PrepateStatementAwareCallback() {
public void fillPrepareStatement(PreparedStatement ps) throws Exception {
ps.setFetchSize(1);
ps.setString(1, name);
}
});
} catch (Exception e) {
if (log.isTraceEnabled()) {
log.trace("Release Lock exception (might be valid) [" + e.getMessage() + "]");
}
}
}
public boolean isLocked() {
try {
return jdbcDirectory.fileExists(name);
} catch (Exception e) {
return false;
}
}
public String toString() {
return "PhantomReadLock[" + name + "/" + jdbcDirectory.getTable() + "]";
}
}