Subject: Normalized Ranking example incorrect in text search
From: Simon Riggs <simon@2ndquadrant.com>
To: pgsql-docs@postgresql.org
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Date: Wed, 14 Nov 2007 06:24:51 +0000
Message-Id: <1195021491.4378.71.camel@ebony.site>
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http://developer.postgresql.org/pgdocs/postgres/textsearch-controls.html
Ranking Search Results

shows and example which says

"This is the same example using normalized ranking"

and then gives a query which calculates normalization in an incorrect
manner, yet without using the normalization parameter. A correct example
would be something like this:

SELECT title, ts_rank_cd(textsearch, query, 8 /*Normalization*/) AS rank
FROM apod, to_tsquery('neutrino|(dark & matter)') query
WHERE query @@ textsearch
ORDER BY rank DESC LIMIT 10;

I can't rerun the query because I don't have the example data set used.
Is that available?

This section also describes the two ranking functions supplied and
suggests you can write your own also.
- Can we say what the differences are between the two ranking functions?
Why do we have two?
- Can we supply or link to an example ranking function to allow people
to write their own?

-- 
  Simon Riggs
  2ndQuadrant  http://www.2ndQuadrant.com