[jira] Commented: (AVRO-545) Move mapreduce bindings out of avro jar

["Scott Carey (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/AVRO-545?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12868901#action_12868901 ] 

Scott Carey commented on AVRO-545:
----------------------------------

The mapreduce dependency in Avro is specified as "optional", which means that consumers of avro do not automatically pull it in as a dependency.  In other words, its not a transitive dependency.  

We can move it to another jar "avro-mapred.jar", but there is only a KB or two difference in jar size at the moment.

{code}
    <dependency>
      <groupId>org.apache.hadoop</groupId>
      <artifactId>hadoop-core</artifactId>
      <version>0.20.2</version>
      <optional>true</optional>
    </dependency>
{code}

In short, if Hadoop 0.22 depends on Avro 1.4, it does not imply that Hadoop 0.22 depends on Hadoop 0.20.2 due to the above "optional" flag.


http://maven.apache.org/guides/introduction/introduction-to-optional-and-excludes-dependencies.html

>From the maven site:
{quote}
How do optional dependencies work?

Project-A -> Project-B

The diagram above says that Project-A depends on Project-B. When A declares B as an optional dependency in its POM, this relationship remains unchanged. Its just like a normal build where Project-B will be added in its classpath.

Project-X -> Project-A

But when another project(Project-X) declares Project-A as a dependency in its POM, the optional dependency takes effect. You'll notice that Project-B is not included in the classpath of Project-X; you will need to declare it directly in your POM in order for B to be included in X's classpath.

{quote}

> Move mapreduce bindings out of avro jar
> ---------------------------------------
>
>                 Key: AVRO-545
>                 URL: https://issues.apache.org/jira/browse/AVRO-545
>             Project: Avro
>          Issue Type: Bug
>          Components: java
>            Reporter: Owen O'Malley
>
> MapReduce should not depend on any jars (eg. avro's main jar) that also depend on the MapReduce jar.

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