Hi Yong,
The *LineRecordReader* has a *FSDataInputStream* named *fileIn.* It then
has a separate *Seekable* named *filePosition*, which is set equal to
*fileIn.* *filePosition.seek()* is never called. In the constructor,
*fileIn.seek()* is called, but never again. For the rest of the class, the
only call made to *filePosition* is *getPos()*. As I mentioned in the
first email, this seems redundant.
The question comes from this bit of code:
> private long getFilePosition() throws IOException {
> long retVal;
> if (isCompressedInput() && null != filePosition) {
> retVal = filePosition.getPos();
> } else {
> retVal = pos;
> }
> return retVal;
> }
That's the only place *filePosition* is used. If there's also a field name
*pos* that tracks the same thing, then why use the *filePosition* at all?
Isn't that just duplicate work?
Thanks for giving me time,
Brian
On Wed, Feb 19, 2014 at 2:55 PM, java8964 <[email protected]> wrote:
> Hi, Brian:
>
> I hope I understand your question correctly. Here is my view what provided
> from the Seekable interface.
>
> The Seekable interface also defines the "seek(long pos)" method, which
> allows the client to seek to a specified position in the underline
> InputStream.
>
> In the RecordReader, it will get the start position and an instance of the
> inputSplit, but the underline input stream is not open or available yet.
>
> The RecordReader will find the correct start position of the stream, and
> use Seekable interface to "seek" the specified start position, and start to
> read the bytes from there, to translates following bytes data into <K, V>
> pairs.
>
> Without Seekable interface, there is no way to "seek" to the correct
> starting position.
>
> Yong
>
> ------------------------------
> Date: Wed, 19 Feb 2014 14:39:00 -0500
> Subject: Question about the usage of Seekable within the LineRecordReader
> From: [email protected]
> To: [email protected]
>
>
> Hi List,
> In order to write my own record reader, I'm taking a look at the
> *LineRecordReader* in v 2.2.0. I notice that it uses *Seekable* in order
> to tell where it is in the file when using something other than an
> *InputStream*. As far as I can see, the only reason its used is to get
> the current position within the file (within *getFilePosition()* ).
>
> My question is: Why? It looks like the file position is already tracked
> by the *pos* field. Is there a reason to use *Seekable.getPos()* instead
> of looking at *pos*?
>
> Thanks for the help,
> Brian
>
