Flexible segment format
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Key: NUTCH-466
URL: https://issues.apache.org/jira/browse/NUTCH-466
Project: Nutch
Issue Type: Improvement
Components: searcher
Affects Versions: 1.0.0
Reporter: Andrzej Bialecki
Assigned To: Andrzej Bialecki
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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