Re: bug in ts_rank_cd

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