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From "Markus Jelsma (JIRA)" <>
Subject [jira] [Closed] (NUTCH-466) Flexible segment format
Date Fri, 01 Apr 2011 14:37:07 GMT


Markus Jelsma closed NUTCH-466.

    Resolution: Won't Fix

> Flexible segment format
> -----------------------
>                 Key: NUTCH-466
>                 URL:
>             Project: Nutch
>          Issue Type: Improvement
>          Components: searcher
>    Affects Versions: 1.0.0
>            Reporter: Andrzej Bialecki 
>            Assignee: Andrzej Bialecki 
>         Attachments:, segmentparts.patch
> In many situations it is necessary to store more data associated with pages than it's
possible now with the current segment format. Quite often it's a binary data. There are two
common workarounds for this: one is to use per-page metadata, either in Content or ParseData,
the other is to use an external independent database using page ID-s as foreign keys.
> Currently segments can consist of the following predefined parts: content, crawl_fetch,
crawl_generate, crawl_parse, parse_text and parse_data. I propose a third option, which is
a natural extension of this existing segment format, i.e. to introduce the ability to add
arbitrarily named segment "parts", with the only requirement that they should be MapFile-s
that store Writable keys and values. Alternatively, we could define a SegmentPart.Writer/Reader
to accommodate even more sophisticated scenarios.
> Existing segment API and searcher API (NutchBean, DistributedSearch Client/Server) should
be extended to handle such arbitrary parts.
> Example applications:
> * storing HTML previews of non-HTML pages, such as PDF, PS and Office documents
> * storing pre-tokenized version of plain text for faster snippet generation
> * storing linguistically tagged text for sophisticated data mining
> * storing image thumbnails
> etc, etc ...
> I'm going to prepare a patchset shortly. Any comments and suggestions are welcome.

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