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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:
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.
was:
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
Serialization Implementations to be known apriori and registered and goes
against the spirit of a very generic FlatFileDeserializeRecordReader. (see
below re: adding Serialization implementations to contrib).
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.
reverting to original description :)
> 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
>
>
> 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.
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