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https://issues.apache.org/jira/browse/HADOOP-4192?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Pete Wyckoff resolved HADOOP-4192.
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Resolution: Invalid
should be attacking this the other way around by having a way of getting
serialization context info - the serialization class and the class to be
deserialized and pass these down.
> Class <? extends T> Deserializer.getRealClass() method to return the actual
> class of the objects from a deserializer
> --------------------------------------------------------------------------------------------------------------------
>
> Key: HADOOP-4192
> URL: https://issues.apache.org/jira/browse/HADOOP-4192
> Project: Hadoop Core
> Issue Type: Bug
> Components: mapred
> Reporter: Pete Wyckoff
>
> Note: this use case is completely for non-self describing files with
> Serialization framework records. If the Serialization Class and the actual
> type of records to be deserialized is configured higher up through the
> JobConf.
> It is motivated by the need to create a generic
> FlatFileDeserializerRecordReader that can be configued to use any
> Serialization implementation through the JobConf.
> Since A deserializer can return a subtype of the type it is instantiated to
> return, we can create generic Deserializers for a base type - e.g., Writable,
> Record, Thrift.Tbase where the RecordReader need not be specific to any of
> them.
> In which case,to implement RecordReader.getValueClass();, the generic
> RecordReader really needs to query that from the Deserializer.
> And since this RecordReader is generic even ithe Serialization Implementation
> it is going to use should come from the JobConf as should the actual specific
> class being Deserialized. e.g., Record/MyUserIDRecord, Writable/LongWritable.
> The RecordReader would need to know how the Serialization and Deserializer
> get their configuration info to implement getValueClass().
> A much cleaner way is to implement getRealClass I think.
>
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