Re: Question about trigram GIST index

[Robert DiFalco <robert.difalco@xxxxxxxxx>]

I'm pretty sure '%John%' uses the index.

explain analyze verbose SELECT name FROM wai_users WHERE lower(name) LIKE '%john%';

                                                          QUERY PLAN                                                          

------------------------------------------------------------------------------------------------------------------------------

 Bitmap Heap Scan on public.wai_users  (cost=53.45..1345.46 rows=900 width=14) (actual time=18.474..32.093 rows=1596 loops=1)

   Output: name

   Recheck Cond: (lower((wai_users.name)::text) ~~ '%john%'::text)

   ->  Bitmap Index Scan on idx_user_name  (cost=0.00..53.41 rows=900 width=0) (actual time=18.227..18.227 rows=1596 loops=1)

         Index Cond: (lower((wai_users.name)::text) ~~ '%john%'::text)

 Total runtime: 33.662 ms

(6 rows)

On Thu, Dec 18, 2014 at 10:00 AM, Giuseppe Broccolo <giuseppe.broccolo@xxxxxxxxxxxxxx> wrote:

I'm not sure about the '%' operator, but I'm sure that the GIST index will never be used in the

  SELECT * FROM users WHERE lower(name) LIKE '%john%';

query; it is used for left or right anchored search, such as 'john%' or '%john'.

Giuseppe.

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Giuseppe Broccolo - 2ndQuadrant Italy
PostgreSQL Training, Services and Support
giuseppe.broccolo@xxxxxxxxxxxxxx | www.2ndQuadrant.it