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 *   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
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package org.apache.cayenne.dba.oracle;

import java.util.List;

import org.apache.cayenne.access.DataNode;
import org.apache.cayenne.access.translator.select.DefaultSelectTranslator;
import org.apache.cayenne.dba.DbAdapter;
import org.apache.cayenne.map.EntityResolver;
import org.apache.cayenne.query.Query;

/**
 * Select translator that implements Oracle-specific optimizations.
 * 
 */
class OracleSelectTranslator extends DefaultSelectTranslator {

	/**
	 * @since 4.0
	 */
	public OracleSelectTranslator(Query query, DbAdapter adapter, EntityResolver entityResolver) {
		super(query, adapter, entityResolver);
	}

	@Override
	protected void appendLimitAndOffsetClauses(StringBuilder buffer) {
		int offset = queryMetadata.getFetchOffset();
		int limit = queryMetadata.getFetchLimit();

		if (limit > 0 || offset > 0) {
			int max = (limit <= 0) ? Integer.MAX_VALUE : limit + offset;

			buffer.insert(0, "select * from ( select tid.*, ROWNUM rnum from (");
			buffer.append(") tid where ROWNUM <=").append(max).append(") where rnum  > ").append(offset);
		}
	}

	@Override
	protected void appendSelectColumns(StringBuilder buffer, List<String> selectColumnExpList) {

		// we need to add aliases to all columns to make fetch
		// limit and offset work properly on Oracle (see CAY-1266)

		// append columns (unroll the loop's first element)
		int columnCount = selectColumnExpList.size();
		buffer.append(selectColumnExpList.get(0));
		if(!selectColumnExpList.get(0).contains(" AS ")) {
			buffer.append(" AS c0");
		}

		// assume there is at least 1 element
		for (int i = 1; i < columnCount; i++) {
			buffer.append(", ");
			buffer.append(selectColumnExpList.get(i));
			if(!selectColumnExpList.get(i).contains(" AS ")) {
				buffer.append(" AS c").append(i);
			}
		}
	}
}