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From "ASF GitHub Bot (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (FLINK-4460) Side Outputs in Flink
Date Fri, 10 Mar 2017 14:18:06 GMT

    [ https://issues.apache.org/jira/browse/FLINK-4460?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15905155#comment-15905155
] 

ASF GitHub Bot commented on FLINK-4460:
---------------------------------------

Github user kl0u commented on a diff in the pull request:

    https://github.com/apache/flink/pull/3484#discussion_r105397933
  
    --- Diff: flink-core/src/main/java/org/apache/flink/util/OutputTag.java ---
    @@ -0,0 +1,115 @@
    +/*
    + * 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.flink.util;
    +
    +import static java.util.Objects.requireNonNull;
    +
    +import java.io.IOException;
    +import java.io.ObjectInputStream;
    +import java.io.Serializable;
    +
    +import org.apache.flink.annotation.PublicEvolving;
    +import org.apache.flink.api.common.functions.InvalidTypesException;
    +import org.apache.flink.api.common.typeinfo.TypeHint;
    +import org.apache.flink.api.common.typeinfo.TypeInformation;
    +
    +
    +/**
    + * An {@link OutputTag} is a typed and named tag to use for tagging side outputs
    + * of an operator.
    + *
    + * <p>An {@code OutputTag} must always be an anonymous inner class so that Flink
can derive
    + * a {@link TypeInformation} for the generic type parameter.
    + *
    + * <p>Example:
    + * <pre>{@code
    + * OutputTag<Tuple2<String, Long>> info = new OutputTag<Tuple2<String,
Long>>("late-data"){});
    + * }</pre>
    + *
    + * @param <T> the type of elements in the side-output stream.
    + */
    +@PublicEvolving
    +public class OutputTag<T> implements Serializable {
    +
    +	private static final long serialVersionUID = 1L;
    +
    +	private final String id;
    +
    +	private transient TypeInformation<T> typeInfo;
    +
    +	/**
    +	 * Creates a new named {@code OutputTag} with the given id.
    +	 *
    +	 * @param id The id of the created {@code OutputTag}.
    +     */
    +	public OutputTag(String id) {
    +		Preconditions.checkNotNull(id, "OutputTag id cannot be null.");
    +		this.id = requireNonNull(id);
    +
    +		try {
    +			TypeHint<T> typeHint =
    +					new TypeHint<T>(OutputTag.class, this, 0) {};
    +			this.typeInfo = typeHint.getTypeInfo();
    +		} catch (InvalidTypesException e) {
    +			throw new InvalidTypesException("Could not determine TypeInformation for generic "
+
    +					"OutputTag type. Did you forget to make your OutputTag an anonymous inner class?",
e);
    +		}
    +	}
    +
    +	/**
    +	 * Creates a new named {@code OutputTag} with the given id and output {@link TypeInformation}.
    +	 *
    +	 * @param id The id of the created {@code OutputTag}.
    +	 * @param typeInfo The {@code TypeInformation} for the side output.
    +	 */
    +	public OutputTag(String id, TypeInformation<T> typeInfo) {
    +		this.id = Preconditions.checkNotNull(id, "OutputTag id cannot be null.");
    +		this.typeInfo =
    +				Preconditions.checkNotNull(typeInfo, "TypeInformation cannot be null.");
    +	}
    +
    +	private void readObject(ObjectInputStream in) throws IOException, ClassNotFoundException
{
    +		in.defaultReadObject();
    +		typeInfo = null;
    +	}
    +
    +	public String getId() {
    +		return id;
    +	}
    +
    +	public TypeInformation<T> getTypeInfo() {
    +		return typeInfo;
    +	}
    +
    +	@Override
    +	public boolean equals(Object obj) {
    +		return obj instanceof OutputTag
    --- End diff --
    
    Two points:
    1) we cannot have `this.id == null` or `(OutputTag) obj).id == null` because we check
at the constructor, so this method can be simplified.
    2) we never check for uniqueness of the `outputTag.id`. We should do it at the translation.
This is also a correctness issue as this may result in undesired sideoutput "collisions.


> Side Outputs in Flink
> ---------------------
>
>                 Key: FLINK-4460
>                 URL: https://issues.apache.org/jira/browse/FLINK-4460
>             Project: Flink
>          Issue Type: New Feature
>          Components: Core, DataStream API
>    Affects Versions: 1.2.0, 1.1.3
>            Reporter: Chen Qin
>            Assignee: Chen Qin
>              Labels: latearrivingevents, sideoutput
>
> https://docs.google.com/document/d/1vg1gpR8JL4dM07Yu4NyerQhhVvBlde5qdqnuJv4LcV4/edit?usp=sharing



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