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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 specific language governing permissions and
* limitations under the License.
*/
package org.apache.solr.client.solrj.io.stream;
import java.io.IOException;
import java.util.ArrayList;
import java.util.List;
import java.util.Locale;
import org.apache.solr.client.solrj.io.Tuple;
import org.apache.solr.client.solrj.io.comp.FieldComparator;
import org.apache.solr.client.solrj.io.comp.StreamComparator;
import org.apache.solr.client.solrj.io.stream.expr.Explanation;
import org.apache.solr.client.solrj.io.stream.expr.Explanation.ExpressionType;
import org.apache.solr.client.solrj.io.stream.expr.Expressible;
import org.apache.solr.client.solrj.io.stream.expr.StreamExplanation;
import org.apache.solr.client.solrj.io.stream.expr.StreamExpression;
import org.apache.solr.client.solrj.io.stream.expr.StreamExpressionNamedParameter;
import org.apache.solr.client.solrj.io.stream.expr.StreamExpressionValue;
import org.apache.solr.client.solrj.io.stream.expr.StreamFactory;
/**
* Merges two or more streams together ordering the Tuples based on a Comparator.
* All streams must be sorted by the fields being compared - this will be validated on construction.
**/
public class MergeStream extends TupleStream implements Expressible {
private static final long serialVersionUID = 1;
private PushBackStream[] streams;
private StreamComparator comp;
public MergeStream(TupleStream streamA, TupleStream streamB, StreamComparator comp) throws IOException {
init(comp, streamA, streamB);
}
public MergeStream(StreamComparator comp, TupleStream ... streams) throws IOException {
init(comp, streams);
}
public MergeStream(StreamExpression expression,StreamFactory factory) throws IOException {
// grab all parameters out
List streamExpressions = factory.getExpressionOperandsRepresentingTypes(expression, Expressible.class, TupleStream.class);
StreamExpressionNamedParameter onExpression = factory.getNamedOperand(expression, "on");
// validate expression contains only what we want.
if(expression.getParameters().size() != streamExpressions.size() + 1){
throw new IOException(String.format(Locale.ROOT,"Invalid expression %s - unknown operands found", expression));
}
if(streamExpressions.size() < 2){
throw new IOException(String.format(Locale.ROOT,"Invalid expression %s - expecting at least two streams but found %d (must be PushBackStream types)",expression, streamExpressions.size()));
}
if(null == onExpression || !(onExpression.getParameter() instanceof StreamExpressionValue)){
throw new IOException(String.format(Locale.ROOT,"Invalid expression %s - expecting single 'on' parameter listing fields to merge on but didn't find one",expression));
}
TupleStream[] streams = new TupleStream[streamExpressions.size()];
for(int idx = 0; idx < streamExpressions.size(); ++idx){
streams[idx] = factory.constructStream(streamExpressions.get(idx));
}
init( factory.constructComparator(((StreamExpressionValue)onExpression.getParameter()).getValue(), FieldComparator.class),
streams
);
}
private void init(StreamComparator comp, TupleStream ... streams) throws IOException {
// All streams must both be sorted so that comp can be derived from
for(TupleStream stream : streams){
if(!comp.isDerivedFrom(stream.getStreamSort())){
throw new IOException("Invalid MergeStream - all substream comparators (sort) must be a superset of this stream's comparator.");
}
}
// Convert to PushBack streams so we can push back tuples
this.streams = new PushBackStream[streams.length];
for(int idx = 0; idx < streams.length; ++idx){
this.streams[idx] = new PushBackStream(streams[idx]);
}
this.comp = comp;
}
@Override
public StreamExpression toExpression(StreamFactory factory) throws IOException{
return toExpression(factory, true);
}
private StreamExpression toExpression(StreamFactory factory, boolean includeStreams) throws IOException {
// function name
StreamExpression expression = new StreamExpression(factory.getFunctionName(this.getClass()));
// streams
for(PushBackStream stream : streams){
if(includeStreams){
expression.addParameter(stream.toExpression(factory));
}
else{
expression.addParameter("");
}
}
// on
expression.addParameter(new StreamExpressionNamedParameter("on",comp.toExpression(factory)));
return expression;
}
@Override
public Explanation toExplanation(StreamFactory factory) throws IOException {
StreamExplanation explanation = new StreamExplanation(getStreamNodeId().toString());
explanation.setFunctionName(factory.getFunctionName(this.getClass()));
explanation.setImplementingClass(this.getClass().getName());
explanation.setExpressionType(ExpressionType.STREAM_DECORATOR);
explanation.setExpression(toExpression(factory, false).toString());
explanation.addHelper(comp.toExplanation(factory));
for(PushBackStream stream : streams){
explanation.addChild(stream.toExplanation(factory));
}
return explanation;
}
public void setStreamContext(StreamContext context) {
for(PushBackStream stream : streams){
stream.setStreamContext(context);
}
}
public List children() {
List l = new ArrayList();
for(PushBackStream stream : streams){
l.add(stream);
}
return l;
}
public void open() throws IOException {
for(PushBackStream stream : streams){
stream.open();
}
}
public void close() throws IOException {
for(PushBackStream stream : streams){
stream.close();
}
}
public Tuple read() throws IOException {
// might be able to optimize this by sorting the streams based on the next to read tuple from each.
// if we can ensure the sort of the streams and update it in less than linear time then there would
// be some performance gain. But, assuming the # of streams is kinda small then this might not be
// worth it
Tuple minimum = null;
PushBackStream minimumStream = null;
for(PushBackStream stream : streams){
Tuple current = stream.read();
if(current.EOF){
stream.pushBack(current);
continue;
}
if(null == minimum){
minimum = current;
minimumStream = stream;
continue;
}
if(comp.compare(current, minimum) < 0){
// Push back on its stream
minimumStream.pushBack(minimum);
minimum = current;
minimumStream = stream;
continue;
}
else{
stream.pushBack(current);
}
}
// If all EOF then min will be null, else min is the current minimum
if(null == minimum){
// return EOF, doesn't matter which cause we're done
return streams[0].read();
}
return minimum;
// Tuple a = streamA.read();
// Tuple b = streamB.read();
//
// if(a.EOF && b.EOF) {
// return a;
// }
//
// if(a.EOF) {
// streamA.pushBack(a);
// return b;
// }
//
// if(b.EOF) {
// streamB.pushBack(b);
// return a;
// }
//
// int c = comp.compare(a,b);
//
// if(c < 0) {
// streamB.pushBack(b);
// return a;
// } else {
// streamA.pushBack(a);
// return b;
// }
}
/** Return the stream sort - ie, the order in which records are returned */
public StreamComparator getStreamSort(){
return comp;
}
public int getCost() {
return 0;
}
}
