[pg_trgm] Making similarity(?, ?) < ? use an index
| От | Greg Navis |
|---|---|
| Тема | [pg_trgm] Making similarity(?, ?) < ? use an index |
| Дата | |
| Msg-id | CAA6WWt834QH-f20okyv6repnHm5oqe-16z0GAdiH4RzPBf9t+A@mail.gmail.com обсуждение исходный текст |
| Ответы |
Re: [pg_trgm] Making similarity(?, ?) < ? use an index
Re: [pg_trgm] Making similarity(?, ?) < ? use an index |
| Список | pgsql-general |
Hey!
I'm playing with pg_trgm. It seems that `lhs % rhs` is _almost_ equivalent to `similarity(lhs, rhs) < show_limit()`. The difference that I noticed is that `%` uses a GIN index while `similarity` does not.
```
grn=# \d restaurants
Table "public.restaurants"
Column | Type | Modifiers
--------+------------------------+-----------
city | character varying(255) | not null
Indexes:
"restaurants_city_trgm_idx" gin (city gin_trgm_ops)
grn=# SELECT COUNT(*) FROM restaurants;
count
--------
515475
(1 row)
Time: 45.964 ms
grn=# EXPLAIN ANALYZE SELECT * FROM restaurants WHERE similarity(city, 'warsw') > show_limit();
QUERY PLAN
--------------------------------------------------------------------------------------------------------------------
Seq Scan on restaurants (cost=0.00..11692.81 rows=171825 width=10) (actual time=16.436..665.062 rows=360 loops=1)
Filter: (similarity((city)::text, 'warsw'::text) > show_limit())
Rows Removed by Filter: 515115
Planning time: 0.139 ms
Execution time: 665.105 ms
(5 rows)
Time: 665.758 ms
```
My question is: is it possible to make `similarity` use the index? If not, is there a way to speed up the query above?
Best regards
--
--
Greg Navis
I help tech companies to scale Heroku-hosted Rails apps.
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