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https://issues.apache.org/jira/browse/HADOOP-4065?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Pete Wyckoff updated HADOOP-4065:
---------------------------------
Description:
Implement generic FlatFileDeserializationRecordReader which assumes a
Serialization Implementation is specific in the JobConf and that once
instantiated, that Serialization Implementation can figure out the actual
class being Deserialized from the JobConf. e.g., the JobConf specifies
RecordIOSerialization and then the specific class is LogRecordObject.
Another way one might to do this is to use the SerializationFactory to do the
lookup of the Serialization Implementation; however, this requires all
Deserializers to be known apriori and registered and goes against the spirit of
a very generic FlatFileDeserializeRecordReader.
To ensure it is generic, I propose implementing the following Serialization
implementations:
1. RecordIOSerialization
2. LineReaderSerialization
3. ThriftSerialization
The first 2 should go in io/serialization and the Thrift one in contrib
somewhere.
was:
like textinputformat - looking for a concrete implementation to read binary
records from a flat file (that may be compressed).
it's assumed that hadoop can't split such a file. so the inputformat can set
splittable to false.
tricky aspects are:
- how to know what class the file contains (has to be in a configuration
somewhere).
- how to determine EOF (would be nice if hadoop can determine EOF and not have
the deserializer throw an exception (which is hard to distinguish from a
exception due to corruptions?)). this is easy for non-compressed streams - for
compressed streams - DecompressorStream has a useful looking getAvailable()
call - except the class is marked package private.
> support for reading binary data from flat files
> -----------------------------------------------
>
> Key: HADOOP-4065
> URL: https://issues.apache.org/jira/browse/HADOOP-4065
> Project: Hadoop Core
> Issue Type: Bug
> Components: mapred
> Reporter: Joydeep Sen Sarma
> Attachments: HADOOP-4065.0.txt, HADOOP-4065.1.txt, ThriftFlatFile.java
>
>
> Implement generic FlatFileDeserializationRecordReader which assumes a
> Serialization Implementation is specific in the JobConf and that once
> instantiated, that Serialization Implementation can figure out the actual
> class being Deserialized from the JobConf. e.g., the JobConf specifies
> RecordIOSerialization and then the specific class is LogRecordObject.
> Another way one might to do this is to use the SerializationFactory to do the
> lookup of the Serialization Implementation; however, this requires all
> Deserializers to be known apriori and registered and goes against the spirit
> of a very generic FlatFileDeserializeRecordReader.
> To ensure it is generic, I propose implementing the following Serialization
> implementations:
> 1. RecordIOSerialization
> 2. LineReaderSerialization
> 3. ThriftSerialization
> The first 2 should go in io/serialization and the Thrift one in contrib
> somewhere.
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