com.blazebit.persistence.impl.dialect.MySQLDbmsLimitHandler Maven / Gradle / Ivy
/*
* Copyright 2014 - 2019 Blazebit.
*
* 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 com.blazebit.persistence.impl.dialect;
import com.blazebit.persistence.impl.function.CyclicUnsignedCounter;
import java.sql.PreparedStatement;
import java.sql.SQLException;
/**
* @author Christian Beikov
* @since 1.2.0
*/
public class MySQLDbmsLimitHandler extends AbstractDbmsLimitHandler {
private static final ThreadLocal threadLocalCounter = new ThreadLocal() {
@Override
protected CyclicUnsignedCounter initialValue() {
return new CyclicUnsignedCounter(-1);
}
};
public MySQLDbmsLimitHandler() {
super(20);
}
public MySQLDbmsLimitHandler(int length) {
super(length);
}
@Override
public boolean supportsVariableLimit() {
return true;
}
/**
* Uses a workaround for limit in IN predicates because of an limitation of MySQL.
* See http://dev.mysql.com/doc/refman/5.0/en/subquery-restrictions.html for reference.
*
*/
@Override
public void applySql(StringBuilder sqlSb, boolean isSubquery, String limit, String offset) {
if (isSubquery) {
// Insert it after the open bracket
sqlSb.insert(1, "select * from (");
}
if (limit != null) {
if (offset != null) {
sqlSb.append(" limit ").append(offset).append(',').append(limit);
} else {
sqlSb.append(" limit ").append(limit);
}
} else if (offset != null) {
// The biggest possible limit to be able to make an OFFSET only query
sqlSb.append(" limit ").append(offset).append(",18446744073709551610");
}
if (isSubquery) {
String limitSubqueryAlias = "_tmp_" + threadLocalCounter.get().incrementAndGet();
sqlSb.append(") as ").append(limitSubqueryAlias);
}
}
@Override
public int bindLimitParametersAtEndOfQuery(Integer limit, Integer offset, PreparedStatement statement, int index) throws SQLException {
if (limit != null) {
if (offset != null) {
statement.setInt(index, offset);
statement.setInt(index + 1, limit);
return 2;
} else {
statement.setInt(index, limit);
return 1;
}
} else if (offset != null) {
statement.setInt(index, offset);
return 1;
}
return 0;
}
}