Is spgist intended to support prefix searches with LIKE?
I ask because, first, it seems like something spgist ought to be good
at (unless I'm confused), and, second, the text_ops opfamily includes
these operators:
~<~(text,text)~<=~(text,text)~>=~(text,text)~>~(text,text)
...which seems to be the same operators that are used for btree
pattern-matching searches:
rhaas=# explain select count(*) from person where last_name like 'WAR%'; QUERY
PLAN
------------------------------------------------------------------------------------------Aggregate
(cost=2519.27..2519.28rows=1 width=0) -> Bitmap Heap Scan on person (cost=24.70..2496.75 rows=9005 width=0)
Filter:(last_name ~~ 'WAR%'::text) -> Bitmap Index Scan on person_tpo (cost=0.00..22.45
rows=900 width=0) Index Cond: ((last_name ~>=~ 'WAR'::text) AND
(last_name ~<~ 'WAS'::text))
(5 rows)
...but when I create an index like this:
create index person_spg on person using spgist (last_name text_ops);
...I can't get LIKE to use it, even if I disable seqscans.
Thoughts?
--
Robert Haas
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company