On Thu, Feb 8, 2018 at 6:26 AM, Adrien Nayrat <adrien.nay...@dalibo.com> wrote:
> Hello, > > While reading [1] I notice $subject operators lacks of explanation in > documentation. > [..] > > > ~<~ less than > ~>~ greater than > ~<=~ less than or equal to > ~>=~ greater than or equal to > > For all, it is a character-by-character comparison regardless of > collation. We > encounter them when we use text_pattern_ops for example : > > create index ON users ( location text_pattern_ops); > explain select * from users where location like 'test%'; > QUERY PLAN > ------------------------------------------------------------ > ------------------------ > Index Scan using users_location_idx1 on users (cost=0.43..2.46 rows=54 > width=201) > Index Cond: ((location ~>=~ 'test'::text) AND (location ~<~ > 'tesu'::text)) > Filter: (location ~~ 'test%'::text) > (3 lignes) > > > Should we add them on this page? > https://www.postgresql.org/docs/devel/static/functions-string.html > > Thanks! > > > 1: https://www.postgresql.org/docs/current/static/spgist- > builtin-opclasses.html > > I'd be inclined to remove those four operators from the spgist page's table and replace them with "LIKE". Then in the text below the table explain that LIKE is implemented using a combination of those four operators. If we do add them to the functions and operators chapter it should be in the pattern matching section: https://www.postgresql.org/docs/devel/static/functions-matching.html 9.7.1 LIKE needs a table containing [!]~~ and [!]~~* added anyway; tacking these on as well and noting them as implementation functions (i.e., not something a user would want to invoke directly typically) would be appropriate. David J.
