Sorry for sounding the false alarm. I was not running the vanilla
postgres and that is why I was seeing that problem. Should have checked
with the vanilla one.
-Sushant
On Tue, 2010-12-21 at 23:03 -0500, Tom Lane wrote:
> Sushant Sinha <sushant354@gmail.com> writes:
> > There is a bug in ts_rank_cd. It does not correctly give rank when the
> > query lexeme is the first one in the tsvector.
>
> Hmm ... I cannot reproduce the behavior you're complaining of.
> You say
>
> > select ts_rank_cd(to_tsvector('english', 'abc sdd'),
> > plainto_tsquery('english', 'abc'));
> > ts_rank_cd
> > ------------
> > 0
>
> but I get
>
> regression=# select ts_rank_cd(to_tsvector('english', 'abc sdd'),
> regression(# plainto_tsquery('english', 'abc'));
> ts_rank_cd
> ------------
> 0.1
> (1 row)
>
> > The problem is that the Cover finding algorithm ignores the lexeme at
> > the 0th position,
>
> As far as I can tell, there is no "0th position" --- tsvector counts
> positions from one. The only way to see pos == 0 in the input to
> Cover() is if the tsvector has been stripped of position information.
> ts_rank_cd is documented to return 0 in that situation. Your patch
> would have the effect of causing it to return some nonzero, but quite
> bogus, ranking.
>
> regards, tom lane