Package org.apache.solr.client.solrj.io.stream

Class ReducerStream

java.lang.Object

org.apache.solr.client.solrj.io.stream.TupleStream

org.apache.solr.client.solrj.io.stream.ReducerStream

All Implemented Interfaces:

Closeable, Serializable, AutoCloseable, Expressible, org.apache.solr.common.MapSerializable, org.apache.solr.common.MapWriter, org.apache.solr.common.NavigableObject

public class ReducerStream
extends TupleStream
implements Expressible

Iterates over a TupleStream and buffers Tuples that are equal based on a comparator. This allows tuples to be grouped by common field(s).

The read() method emits one tuple per group. The fields of the emitted Tuple reflect the first tuple encountered in the group.

Use the Tuple.getMaps() method to return all the Tuples in the group. This method returns a list of maps (including the group head), which hold the data for each Tuple in the group.

Note: The ReducerStream requires that it's underlying stream be sorted and partitioned by the same fields as it's comparator.

Since:

5.1.0

See Also:

Serialized Form

Nested Class Summary

Nested classes/interfaces inherited from class org.apache.solr.client.solrj.io.stream.TupleStream

TupleStream.IgnoreException

Nested classes/interfaces inherited from interface org.apache.solr.common.MapWriter

org.apache.solr.common.MapWriter.EntryWriter

Field Summary

Fields inherited from interface org.apache.solr.common.MapWriter

EMPTY

Constructor Summary

Constructors

Constructor	Description
ReducerStream(StreamExpression expression, StreamFactory factory)
ReducerStream(TupleStream stream, StreamComparator comp, ReduceOperation op)
ReducerStream(TupleStream stream, StreamEqualitor eq, ReduceOperation op)

Method Summary

Modifier and Type	Method	Description
List<TupleStream>	children()
void	close()
int	getCost()
StreamComparator	getStreamSort()	Return the stream sort - ie, the order in which records are returned
void	open()
Tuple	read()
void	setStreamContext(StreamContext context)
Explanation	toExplanation(StreamFactory factory)	Returns an explanation about the stream object
StreamExpression	toExpression(StreamFactory factory)

Methods inherited from class org.apache.solr.client.solrj.io.stream.TupleStream

getShards, getShards, getStreamNodeId, writeMap

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Methods inherited from interface org.apache.solr.common.MapWriter

append, jsonStr, toMap

Methods inherited from interface org.apache.solr.common.NavigableObject

_forEachEntry, _forEachEntry, _forEachEntry, _get, _get, _getStr, _getStr, _size

Constructor Detail

ReducerStream

public ReducerStream(TupleStream stream,
                     StreamEqualitor eq,
                     ReduceOperation op)
              throws IOException

Throws:

IOException

ReducerStream

public ReducerStream(TupleStream stream,
                     StreamComparator comp,
                     ReduceOperation op)
              throws IOException

Throws:

IOException

ReducerStream

public ReducerStream(StreamExpression expression,
                     StreamFactory factory)
              throws IOException

Throws:

IOException

Method Detail

toExpression

public StreamExpression toExpression(StreamFactory factory)
                              throws IOException

Specified by:

toExpression in interface Expressible

Throws:

IOException

toExplanation

public Explanation toExplanation(StreamFactory factory)
                          throws IOException

Description copied from interface: Expressible

Returns an explanation about the stream object

Specified by:

toExplanation in interface Expressible

Specified by:

toExplanation in class TupleStream

Parameters:

factory - Stream factory for this, contains information about the function name

Returns:

Explanation about this stream object containing explanations of any child stream objects

Throws:

IOException - throw on any error

setStreamContext

public void setStreamContext(StreamContext context)

Specified by:

setStreamContext in class TupleStream

children

public List<TupleStream> children()

Specified by:

children in class TupleStream

open

public void open()
          throws IOException

Specified by:

open in class TupleStream

Throws:

IOException

close

public void close()
           throws IOException

Specified by:

close in interface AutoCloseable

Specified by:

close in interface Closeable

Specified by:

close in class TupleStream

Throws:

IOException

read

public Tuple read()
           throws IOException

Specified by:

read in class TupleStream

Throws:

IOException

getStreamSort

public StreamComparator getStreamSort()

Return the stream sort - ie, the order in which records are returned

Specified by:

getStreamSort in class TupleStream

getCost

public int getCost()

Overrides:

getCost in class TupleStream