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From "Steve Loughran (JIRA)" <j...@apache.org>
Subject [jira] [Created] (HADOOP-15606) FSDataInputStream/FSInputStream to implement a length()/size() method for amount of data
Date Sat, 14 Jul 2018 15:37:00 GMT
Steve Loughran created HADOOP-15606:
---------------------------------------

             Summary: FSDataInputStream/FSInputStream to implement a length()/size() method
for amount of data
                 Key: HADOOP-15606
                 URL: https://issues.apache.org/jira/browse/HADOOP-15606
             Project: Hadoop Common
          Issue Type: Improvement
          Components: fs, fs/s3
    Affects Versions: 3.1.0
            Reporter: Steve Loughran


server-side transcoding, predicate-pushdown filtering in storage, client-side decryption can
all result in an input stream shorter or longer than the file size as measured in getFileStatus/listFiles/listStatus.


Assuming the length is known once open() returns, the FSDataInputStream can return the length
of the data, which can then be used for accurate seeks within the data.

* requires the streams to know their length; easy to check (hasCapabilities), or make the
new method return an Optional<Long>, but caller will need to (a) look for this if present
and (b) fall back.
* Could be rolled out for all our own clients/connectors, would take time for others



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