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From "Doug Cutting (JIRA)" <j...@apache.org>
Subject [jira] Commented: (LUCENE-756) Maintain norms in a single file .nrm
Date Thu, 21 Dec 2006 18:48:22 GMT
    [ http://issues.apache.org/jira/browse/LUCENE-756?page=comments#action_12460313 ] 
            
Doug Cutting commented on LUCENE-756:
-------------------------------------

Since we're adding a new file, shouldn't we give it a header, so that it's format can be revised?
 Something like:
  new byte[] {'N','R','M',VERSION}
as the first four bytes.  We might someday decide to change the representation used, e.g.,
a different one-byte-float format, or permit higher resolution, or compression, or somesuch.

Also, should we use a constant for ".nrm" extension, so that it's checked at compile-time?

> Maintain norms in a single file .nrm
> ------------------------------------
>
>                 Key: LUCENE-756
>                 URL: http://issues.apache.org/jira/browse/LUCENE-756
>             Project: Lucene - Java
>          Issue Type: Improvement
>          Components: Index
>            Reporter: Doron Cohen
>         Assigned To: Doron Cohen
>            Priority: Minor
>         Attachments: nrm.patch.txt
>
>
> Non-compound indexes are ~10% faster at indexing, and perform 50% IO activity comparing
to compound indexes. But their file descriptors foot print is much higher. 
> By maintaining all field norms in a single .nrm file, we can bound the number of files
used by non compound indexes, and possibly allow more applications to use this format.
> More details on the motivation for this in: http://www.nabble.com/potential-indexing-perormance-improvement-for-compound-index---cut-IO---have-more-files-though-tf2826909.html
(in particular http://www.nabble.com/Re%3A-potential-indexing-perormance-improvement-for-compound-index---cut-IO---have-more-files-though-p7910403.html).

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