Re: TS: Limited cover density ranking

I suggest you work on more general approach, see 
http://www.sai.msu.su/~megera/wiki/2009-08-12 for example.

btw, I don't like you changed ts_rank_cd arguments.

Oleg
On Fri, 27 Jan 2012, karavelov@mail.bg wrote:

> Hello,
>
> I have developed a variation of cover density ranking functions that counts only covers that are lesser than a specified limit. It is useful for finding combinations of terms that appear nearby one another. Here is an example of usage:
>
> -- normal cover density ranking : not changed
> luben=> select ts_rank_cd(to_tsvector('a b c d e g h i j k'), to_tsquery('a&d'));
> ts_rank_cd
> ------------
>  0.0333333
> (1 row)
>
> -- limited to 2
> luben=> select ts_rank_cd(2, to_tsvector('a b c d e g h i j k'), to_tsquery('a&d'));
> ts_rank_cd
> ------------
>          0
> (1 row)
>
> luben=> select ts_rank_cd(2, to_tsvector('a b c d e g h i j k a d'), to_tsquery('a&d'));
> ts_rank_cd
> ------------
>        0.1
> (1 row)
>
> -- limited to 3
> luben=> select ts_rank_cd(3, to_tsvector('a b c d e g h i j k'), to_tsquery('a&d'));
> ts_rank_cd
> ------------
>  0.0333333
> (1 row)
>
> luben=> select ts_rank_cd(3, to_tsvector('a b c d e g h i j k a d'), to_tsquery('a&d'));
> ts_rank_cd
> ------------
>   0.133333
> (1 row)
>
> Find attached a path agains 9.1.2 sources. I preferred to make a patch, not a separate extension because it is only 1 statement change in calc_rank_cd function. If I have to make an extension a lot of code would be duplicated between backend/utils/adt/tsrank.c and the extension.
>
> I have some questions:
>
> 1. Is it interesting to develop it further (documentation, cleanup, etc) for inclusion in one of the next versions? If this is the case, there are some further questions:
>
> - should I overload ts_rank_cd (as in examples above and the patch) or should I define new set of functions, for example ts_rank_lcd ?
> - should I define define this new sql level functions in core or should I go only with this 2 lines change in calc_rank_cd() and define the new functions as an extension? If we prefer the later, could I overload core functions with functions defined in extensions?
> - and finally there is always the possibility to duplicate the code and make an independent extension.
>
> 2. If I run the patched version on cluster that was initialized with unpatched server, is there a way to register the new functions in the system catalog without reinitializing the cluster?
>
> Best regards
> luben
>
> --
> Luben Karavelov

 	Regards,
 		Oleg
_____________________________________________________________
Oleg Bartunov, Research Scientist, Head of AstroNet (www.astronet.ru),
Sternberg Astronomical Institute, Moscow University, Russia
Internet: oleg@sai.msu.su, http://www.sai.msu.su/~megera/
phone: +007(495)939-16-83, +007(495)939-23-83