Search Postgresql Archives

Re: Grouping By Similarity (using pg_trgm)?

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

 



That produces pretty much the same results as the CROSS JOIN I was using before.  Because each "my_value" in the table are different, if I group on just their value then I will always have the full result set and a bunch of essentially duplicated results.

Any other ideas/options?

On Thu, May 14, 2015 at 12:08 PM David G. Johnston <david.g.johnston@xxxxxxxxx> wrote:

On Thu, May 14, 2015 at 11:58 AM, Cory Tucker <cory.tucker@xxxxxxxxx> wrote:
[pg version 9.3 or 9.4]

Suppose I have a simple table:

create table data (
  my_value  TEXT NOT NULL
);
CREATE INDEX idx_my_value ON data USING gin(my_value gin_trgm_ops);


Now I would like to essentially do group by to get a count of all the values that are sufficiently similar.  I can do it using something like a CROSS JOIN to join the table on itself, but then I still am getting all the rows with duplicate counts.  

Is there a way to do a group by query and only return a single "my_value" column and a count of the number of times other values are similar while also not returning the included similar values in the output, too?


​Concept below - not bothering to lookup the functions/operators for pg_trgm:

SELECT my_value_src, count(*)
FROM (SELECT my_value AS my_value_src FROM data) src
JOIN (SELECT my_value AS my_value_compareto FROM data) comparedto
ON ( func(my_value_src, my_value_compareto) < # )
GROUP BY my_value_src

​David J.


[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
[Index of Archives]     [Postgresql Jobs]     [Postgresql Admin]     [Postgresql Performance]     [Linux Clusters]     [PHP Home]     [PHP on Windows]     [Kernel Newbies]     [PHP Classes]     [PHP Books]     [PHP Databases]     [Postgresql & PHP]     [Yosemite]
  Powered by Linux