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https://issues.apache.org/jira/browse/HADOOP-5452?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12680755#action_12680755
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he yongqiang commented on HADOOP-5452:
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Hong,that's right for SequenceFile,maybe in the sequecefile it is needed for
the strict type check, since we don't want add additional information to record
key's and value's class name.
How about relax the strict type check in the MapTask? As you can see from this
issue's description, I encountered this error in MapTask.
I want the mapper and reducer classes in our project more clear/clean and donot
need to convert everytime we use the types. So I am afraid that I can not take
the wrapper solution. Or there other solution?
> Relax the strict type check by allowing subclasses pass the check
> -----------------------------------------------------------------
>
> Key: HADOOP-5452
> URL: https://issues.apache.org/jira/browse/HADOOP-5452
> Project: Hadoop Core
> Issue Type: Improvement
> Reporter: he yongqiang
>
> The type check like:
> {code}
> if (key.getClass() != keyClass)
> throw new IOException("wrong key class: "+key.getClass().getName()
> +" is not "+keyClass);
> if (val.getClass() != valClass)
> throw new IOException("wrong value class: "+val.getClass().getName()
> +" is not "+valClass);
> {code}
> is used a lot when a type check is needed.
> I found their uses in org.apache.hadoop.io.SequenceFile,
> org.apache.hadoop.mapred.IFile, org.apache.hadoop.mapred.MapTask. Because i
> search with(key.getClass() != keyClass), so these codes may also appear in
> other classes.
> I suggest we can relax the strict type check by using
> {code}
> if (key.getClass().isAssignableFrom(keyClass))
> {code}
> The error in my situation is listed below:
> {panel:borderStyle=dashed| borderColor=#ccc| titleBGColor=#F7D6C1|
> bgColor=#FFFFCE}
> java.io.IOException: Type mismatch in value from map: expected
> cn.ac.ict.vega.type.Type, recieved cn.ac.ict.vega.type.Type$Float
> at
> org.apache.hadoop.mapred.MapTask$MapOutputBuffer.collect(MapTask.java:553)
> at
> cn.ac.ict.vega.parse.mapreduce.block.FilterColumnBlockMapper.map(FilterColumnBlockMapper.java:77)
> at
> cn.ac.ict.vega.parse.mapreduce.block.BlockMapRunner.run(BlockMapRunner.java:33)
> at org.apache.hadoop.mapred.MapTask.run(MapTask.java:332)
> at org.apache.hadoop.mapred.Child.main(Child.java:155)
> {panel}
> Float is a sub class of Type. I wish it can pass the check. I use Type
> instead of Float is because i can not determint exactly whether it is Float,
> String or some others.
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