HopRewriteRule.java

/**
 * (C) Copyright IBM Corp. 2010, 2015
 *
 * 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.ibm.bi.dml.hops.rewrite;

import java.util.ArrayList;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;

import com.ibm.bi.dml.hops.Hop;
import com.ibm.bi.dml.hops.HopsException;

/**
 * Base class for all hop rewrites in order to enable generic
 * application of all rules.
 * 
 */
public abstract class HopRewriteRule 
{


	protected static final Log LOG = LogFactory.getLog(HopRewriteRule.class.getName());
		
	/**
	 * Handle a generic (last-level) hop DAG with multiple roots.
	 * 
	 * @param roots
	 * @param state
	 * @return
	 * @throws HopsException
	 */
	public abstract ArrayList<Hop> rewriteHopDAGs( ArrayList<Hop> roots, ProgramRewriteStatus state ) 
		throws HopsException;
	
	/**
	 * Handle a predicate hop DAG with exactly one root.
	 * 
	 * @param root
	 * @param state
	 * @return
	 * @throws HopsException
	 */
	public abstract Hop rewriteHopDAG( Hop root, ProgramRewriteStatus state ) 
		throws HopsException;
}