| /** |
| * 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.metamodel.jdbc.dialects; |
| |
| import org.apache.metamodel.jdbc.JdbcDataContext; |
| import org.apache.metamodel.query.Query; |
| |
| /** |
| * Query rewriter for databases that support LIMIT and OFFSET keywords for max |
| * rows and first row properties. |
| */ |
| public abstract class LimitOffsetQueryRewriter extends DefaultQueryRewriter { |
| |
| public LimitOffsetQueryRewriter(JdbcDataContext dataContext) { |
| super(dataContext); |
| } |
| |
| @Override |
| public final boolean isFirstRowSupported() { |
| return true; |
| } |
| |
| @Override |
| public final boolean isMaxRowsSupported() { |
| return true; |
| } |
| |
| /** |
| * {@inheritDoc} |
| * |
| * If the Max rows and/or First row property of the query is set, then we |
| * will use the database's LIMIT and OFFSET functions. |
| */ |
| @Override |
| public String rewriteQuery(Query query) { |
| String queryString = super.rewriteQuery(query); |
| Integer maxRows = query.getMaxRows(); |
| Integer firstRow = query.getFirstRow(); |
| if (maxRows != null || firstRow != null) { |
| if (maxRows == null) { |
| maxRows = Integer.MAX_VALUE; |
| } |
| queryString = queryString + " LIMIT " + maxRows; |
| |
| if (firstRow != null && firstRow > 1) { |
| // offset is 0-based |
| int offset = firstRow - 1; |
| queryString = queryString + " OFFSET " + offset; |
| } |
| } |
| |
| |
| return queryString; |
| } |
| } |