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