/*
 * Copyright 2002-2014 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.springframework.jdbc.support.incrementer;

import javax.sql.DataSource;

/**
 * {@link DataFieldMaxValueIncrementer} that increments the maximum value of a given HSQL table
 * with the equivalent of an auto-increment column. Note: If you use this class, your HSQL
 * key column should <i>NOT</i> be auto-increment, as the sequence table does the job.
 *
 * <p>The sequence is kept in a table. There should be one sequence table per
 * table that needs an auto-generated key.
 *
 * <p>Example:
 *
 * <pre class="code">create table tab (id int not null primary key, text varchar(100));
 * create table tab_sequence (value identity);
 * insert into tab_sequence values(0);</pre>
 *
 * If "cacheSize" is set, the intermediate values are served without querying the
 * database. If the server or your application is stopped or crashes or a transaction
 * is rolled back, the unused values will never be served. The maximum hole size in
 * numbering is consequently the value of cacheSize.
 *
 * <p><b>NOTE:</b> HSQL now supports sequences and you should consider using them instead:
 * {@link HsqlSequenceMaxValueIncrementer}
 *
 * @author Jean-Pierre Pawlak
 * @author Thomas Risberg
 * @author Juergen Hoeller
 * @see HsqlSequenceMaxValueIncrementer
 */
public class HsqlMaxValueIncrementer extends AbstractIdentityColumnMaxValueIncrementer {

	/**
	 * Default constructor for bean property style usage.
	 * @see #setDataSource
	 * @see #setIncrementerName
	 * @see #setColumnName
	 */
	public HsqlMaxValueIncrementer() {
	}

	/**
	 * Convenience constructor.
	 * @param dataSource the DataSource to use
	 * @param incrementerName the name of the sequence/table to use
	 * @param columnName the name of the column in the sequence table to use
	 */
	public HsqlMaxValueIncrementer(DataSource dataSource, String incrementerName, String columnName) {
		super(dataSource, incrementerName, columnName);
	}


	@Override
	protected String getIncrementStatement() {
		return "insert into " + getIncrementerName() + " values(null)";
	}

	@Override
	protected String getIdentityStatement() {
		return "select max(identity()) from " + getIncrementerName();
	}

}
