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Sequential File

Posted: Tue May 29, 2012 2:08 am
by PhaniKonagalla
Hi,

Can we use UNIX commands in Sequential file stage other than FileName.
Can the Sequential file run in parallel?

Posted: Tue May 29, 2012 3:33 am
by ray.wurlod
Yes and yes.

You can use any well-formed UNIX command as a Filter. The Sequential File stage will consume stdout from the filter command.

The Sequential File stage can run in parallel if you specify multiple readers per node or specify that it is to read more than one file.

Posted: Tue May 29, 2012 3:53 am
by zulfi123786
you could also read a file parallely by specifying multiple nodes per reader provided its a fixed width file.

Posted: Tue May 29, 2012 3:57 am
by zulfi123786
ray.wurlod wrote:The Sequential File stage can run in parallel if you specify multiple readers per node or specify that it is to read more than one file.
When a file pattern is used, it was my assumption that the files are concatenated and the result is read sequentially. with the above quote does it mean the files are read in parallel, if yes then is it one reader per file ?

Posted: Tue May 29, 2012 9:02 am
by jwiles
Your assumption is correct as far as the default operation of the stage is concerned when using a file pattern: It will concatenate the files prior to reading them.

The files which match a pattern can be read in parallel if the environment variable <a href="http://publib.boulder.ibm.com/infocente ... FILESET</a> is set. The underlying operator then will read the files as if they were members of a fileset. IIRC it will be one reader per file, up to the degree of parallelism in which your job is running.

Regards,