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From mjsax <...@git.apache.org>
Subject [GitHub] flink pull request: [FLINK-1967] Introduce (Event)time in Streamin...
Date Fri, 03 Jul 2015 17:10:49 GMT
Github user mjsax commented on a diff in the pull request:

    https://github.com/apache/flink/pull/879#discussion_r33874602
  
    --- Diff: flink-staging/flink-streaming/flink-streaming-core/src/main/java/org/apache/flink/streaming/runtime/streamrecord/StreamRecord.java
---
    @@ -17,87 +17,104 @@
     
     package org.apache.flink.streaming.runtime.streamrecord;
     
    -import java.io.Serializable;
    -
    -import org.apache.flink.api.java.functions.KeySelector;
    -import org.apache.flink.api.java.tuple.Tuple;
    +import org.joda.time.Instant;
     
     /**
    - * Object for wrapping a tuple or other object with ID used for sending records
    - * between streaming task in Apache Flink stream processing.
    + * One value in a data stream. This stores the value and the associated timestamp.
      */
    -public class StreamRecord<T> implements Serializable {
    -	private static final long serialVersionUID = 1L;
    +public class StreamRecord<T> {
     
    -	private T streamObject;
    -	public boolean isTuple;
    +	// We store it as Object so that we can reuse a StreamElement for emitting
    +	// elements of a different type while still reusing the timestamp.
    +	private Object value;
    +	private Instant timestamp;
     
     	/**
    -	 * Creates an empty StreamRecord
    +	 * Creates a new {@link StreamRecord} wrapping the given value. The timestamp is set
to the
    +	 * result of {@code new Instant(0)}.
     	 */
    -	public StreamRecord() {
    +	public StreamRecord(T value) {
    +		this(value, new Instant(0));
     	}
     
     	/**
    -	 * Gets the wrapped object from the StreamRecord
    -	 * 
    -	 * @return The object wrapped
    +	 * Creates a new {@link StreamRecord} wrapping the given value. The timestamp is set
to the
    +	 * given timestamp.
     	 */
    -	public T getObject() {
    -		return streamObject;
    +	public StreamRecord(T value, Instant timestamp) {
    +		this.value = value;
    +		this.timestamp = timestamp;
     	}
     
    +
     	/**
    -	 * Gets the field of the contained object at the given position. If a tuple
    -	 * is wrapped then the getField method is invoked. If the StreamRecord
    -	 * contains and object of Basic types only position 0 could be returned.
    -	 * 
    -	 * @param pos
    -	 *            Position of the field to get.
    -	 * @return Returns the object contained in the position.
    +	 * Returns the value wrapped in this stream value.
     	 */
    -	public Object getField(int pos) {
    -		if (isTuple) {
    -			return ((Tuple) streamObject).getField(pos);
    -		} else {
    -			if (pos == 0) {
    -				return streamObject;
    -			} else {
    -				throw new IndexOutOfBoundsException();
    -			}
    -		}
    +	@SuppressWarnings("unchecked")
    +	public T getValue() {
    +		return (T) value;
     	}
     
     	/**
    -	 * Extracts key for the stored object using the keySelector provided.
    -	 * 
    -	 * @param keySelector
    -	 *            KeySelector for extracting the key
    -	 * @return The extracted key
    +	 * Returns the timestamp associated with this stream value/
     	 */
    -	public <R> R getKey(KeySelector<T, R> keySelector) {
    -		try {
    -			return keySelector.getKey(streamObject);
    -		} catch (Exception e) {
    -			throw new RuntimeException("Failed to extract key: " + e.getMessage());
    -		}
    +	public Instant getTimestamp() {
    +		return timestamp;
    +	}
    +
    +	/**
    +	 * Replace the currently stored value by the given new value. This returns a StreamElement
    +	 * with the generic type parameter that matches the new value while keeping the old
    +	 * timestamp.
    +	 *
    +	 * @param element Element to set in this stream value
    +	 * @return Returns the StreamElement with replaced value
    +	 */
    +	@SuppressWarnings("unchecked")
    +	public <X> StreamRecord<X> replace(X element) {
    +		this.value = element;
    +		return (StreamRecord<X>) this;
     	}
     
     	/**
    -	 * Sets the object stored
    -	 * 
    -	 * @param object
    -	 *            Object to set
    -	 * @return Returns the StreamRecord object
    +	 * Replace the currently stored value by the given new value and the currently stored
    +	 * timestamp with the new timestamp. This returns a StreamElement with the generic type
    +	 * parameter that matches the new value.
    +	 *
    +	 * @param element Element The new value
    +	 * @param timestamp The new timestamp
    +	 * @return Returns the StreamElement with replaced value
     	 */
    -	public StreamRecord<T> setObject(T object) {
    -		this.streamObject = object;
    -		return this;
    +	@SuppressWarnings("unchecked")
    +	public <X> StreamRecord<X> replace(X element, Instant timestamp) {
    --- End diff --
    
    I see. Makes sense. Still using generics seems to be the wrong approach to me. I would
got with Object type instead of T and X and add casts when using StreamRecord. This make the
changing type more explicit.


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