src/main/java/org/apache/sysds/runtime/instructions/spark/FrameAppendMSPInstruction.java

/*
 * 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.sysds.runtime.instructions.spark;

import org.apache.spark.api.java.JavaPairRDD;
import org.apache.spark.api.java.function.PairFlatMapFunction;
import org.apache.sysds.hops.OptimizerUtils;
import org.apache.sysds.runtime.DMLRuntimeException;
import org.apache.sysds.runtime.controlprogram.context.ExecutionContext;
import org.apache.sysds.runtime.controlprogram.context.SparkExecutionContext;
import org.apache.sysds.runtime.instructions.cp.CPOperand;
import org.apache.sysds.runtime.instructions.spark.data.LazyIterableIterator;
import org.apache.sysds.runtime.instructions.spark.data.PartitionedBroadcast;
import org.apache.sysds.runtime.matrix.data.FrameBlock;
import org.apache.sysds.runtime.matrix.operators.Operator;
import scala.Tuple2;

import java.util.Iterator;

public class FrameAppendMSPInstruction extends AppendMSPInstruction {

	protected FrameAppendMSPInstruction(Operator op, CPOperand in1, CPOperand in2, CPOperand offset, CPOperand out,
			boolean cbind, String opcode, String istr) {
		super(op, in1, in2, offset, out, cbind, opcode, istr);
	}

	@Override
	public void processInstruction(ExecutionContext ec) {
		// map-only append (rhs must be vector and fit in mapper mem)
		SparkExecutionContext sec = (SparkExecutionContext)ec;
		checkBinaryAppendInputCharacteristics(sec, _cbind, false, false);
		
		JavaPairRDD<Long,FrameBlock> in1 = sec.getFrameBinaryBlockRDDHandleForVariable( input1.getName() );
		PartitionedBroadcast<FrameBlock> in2 = sec.getBroadcastForFrameVariable( input2.getName() );
		
		//execute map-append operations (partitioning preserving if keys for blocks not changing)
		JavaPairRDD<Long,FrameBlock> out = null;
		if( preservesPartitioning(_cbind) ) {
			out = in1.mapPartitionsToPair(
					new MapSideAppendPartitionFunction(in2), true);
		}
		else 
			throw new DMLRuntimeException("Append type rbind not supported for frame mappend, instead use rappend");
		
		//put output RDD handle into symbol table
		updateBinaryAppendOutputDataCharacteristics(sec, _cbind);
		sec.setRDDHandleForVariable(output.getName(), out);
		sec.addLineageRDD(output.getName(), input1.getName());
		sec.addLineageBroadcast(output.getName(), input2.getName());
		
		//update schema of output with merged input schemas
		sec.getFrameObject(output.getName()).setSchema(
			sec.getFrameObject(input1.getName()).mergeSchemas(
			sec.getFrameObject(input2.getName())));
	}

	private static boolean preservesPartitioning( boolean cbind ) {
		//Partitions for input1 will be preserved in case of cbind, 
		// where as in case of rbind partitions will not be preserved.
		return cbind;
	}

	private static class MapSideAppendPartitionFunction implements  PairFlatMapFunction<Iterator<Tuple2<Long,FrameBlock>>, Long, FrameBlock> 
	{
		private static final long serialVersionUID = -3997051891171313830L;

		private PartitionedBroadcast<FrameBlock> _pm = null;
		
		public MapSideAppendPartitionFunction(PartitionedBroadcast<FrameBlock> binput)  
		{
			_pm = binput;
		}

		@Override
		public LazyIterableIterator<Tuple2<Long, FrameBlock>> call(Iterator<Tuple2<Long, FrameBlock>> arg0)
			throws Exception 
		{
			return new MapAppendPartitionIterator(arg0);
		}
		
		/**
		 * Lazy mappend iterator to prevent materialization of entire partition output in-memory.
		 * The implementation via mapPartitions is required to preserve partitioning information,
		 * which is important for performance. 
		 */
		private class MapAppendPartitionIterator extends LazyIterableIterator<Tuple2<Long, FrameBlock>>
		{
			public MapAppendPartitionIterator(Iterator<Tuple2<Long, FrameBlock>> in) {
				super(in);
			}

			@Override
			protected Tuple2<Long, FrameBlock> computeNext(Tuple2<Long, FrameBlock> arg)
				throws Exception
			{
				Long ix = arg._1();
				FrameBlock in1 = arg._2();
			
				int rowix = (ix.intValue()-1)/OptimizerUtils.DEFAULT_FRAME_BLOCKSIZE+1;
				int colix = 1;
				
				FrameBlock in2 = _pm.getBlock(rowix, colix);
				FrameBlock out = in1.append(in2, new FrameBlock(), true); //cbind
				return new Tuple2<>(ix, out);
			}			
		}
	}
}