Re: index on ILIKE/LIKE - PostgreSQL 9.2 - Mailing list pgsql-general

På torsdag 12. mai 2016 kl. 02:30:33, skrev Lucas Possamai <drum.lucas@gmail.com>:

Hi there!

 

I've got a simple but slow query:

 

 SELECT DISTINCT title  
FROM ja_jobs WHERE title ILIKE '%RYAN WER%'
and clientid = 31239  AND time_job > 1457826264
order BY title
limit 10

 

Explain analyze: 

 

Limit  (cost=5946.40..5946.41 rows=1 width=19) (actual time=2746.759..2746.772 rows=1 loops=1)
  ->  Unique  (cost=5946.40..5946.41 rows=1 width=19) (actual time=2746.753..2746.763 rows=1 loops=1)
        ->  Sort  (cost=5946.40..5946.41 rows=1 width=19) (actual time=2746.750..2746.754 rows=4 loops=1)
              Sort Key: "title"
              Sort Method: quicksort  Memory: 25kB
              ->  Bitmap Heap Scan on "ja_jobs"  (cost=49.02..5946.39 rows=1 width=19) (actual time=576.275..2746.609 rows=4 loops=1)
                    Recheck Cond: (("clientid" = 31239) AND ("time_job" > 1457826264))
                    Filter: (("title")::"text" ~~* '%RYAN WER%'::"text")
                    Rows Removed by Filter: 791
                    ->  Bitmap Index Scan on "ix_jobs_client_times"  (cost=0.00..49.02 rows=1546 width=0) (actual time=100.870..100.870 rows=795 loops=1)
                          Index Cond: (("clientid" = 31239) AND ("time_job" > 1457826264))
Total runtime: 2746.879 ms

 

Then, I created a trgm index:

 

CREATE INDEX ix_ja_jobs_trgm_gin ON public.ja_jobs USING gin (title gin_trgm_ops);

 

Explain analyze after the index: (Yes, I ran the analyze)

 

Limit  (cost=389.91..389.91 rows=1 width=20) (actual time=3720.511..3720.511 rows=0 loops=1)
  ->  Unique  (cost=389.91..389.91 rows=1 width=20) (actual time=3720.507..3720.507 rows=0 loops=1)
        ->  Sort  (cost=389.91..389.91 rows=1 width=20) (actual time=3720.505..3720.505 rows=0 loops=1)
              Sort Key: "title"
              Sort Method: quicksort  Memory: 25kB
              ->  Bitmap Heap Scan on "ja_jobs"  (cost=385.88..389.90 rows=1 width=20) (actual time=3720.497..3720.497 rows=0 loops=1)
                    Recheck Cond: (("clientid" = 31239) AND ("time_job" > 1457826264) AND (("title")::"text" ~~ '%RYAN WER%'::"text"))
                    Rows Removed by Index Recheck: 4
                    ->  BitmapAnd  (cost=385.88..385.88 rows=1 width=0) (actual time=3720.469..3720.469 rows=0 loops=1)
                          ->  Bitmap Index Scan on "ix_jobs_client_times"  (cost=0.00..50.00 rows=1644 width=0) (actual time=0.142..0.142 rows=795 loops=1)
                                Index Cond: (("clientid" = 31239) AND ("time_job" > 1457826264))
                          ->  Bitmap Index Scan on "ix_ja_jobs_trgm_gin"  (cost=0.00..335.63 rows=484 width=0) (actual time=3720.213..3720.213 rows=32 loops=1)
                                Index Cond: (("title")::"text" ~~ '%RYAN WER%'::"text")
Total runtime: 3720.653 ms 

 

 

so.. the query is still slow.. 

Do you guys  know what can be done ? related to the ILIKE?

 

cheers

Lucas

 

It uses available indexes, but that isn't good enough.

 

Try including clientid in the index, using the btree_gin extension:

 

CREATE INDEX ix_ja_jobs_trgm_clientid_gin ON public.ja_jobs USING gin (title gin_trgm_ops, clientid);

 

Note that if clientid is a bigint you have to cast the value to bigint for btree_gin to use it (note that this isn't necessary if you use a prepared statement):

 

SELECT DISTINCT title  
        FROM ja_jobs WHERE title ILIKE '%RYAN WER%'
        and clientid = 31239::bigint  AND time_job > 1457826264
        order BY title
        limit 10

 

Also note that the index cannot ant won't be used for sorting. A bitmap-AND is also inevitable because GIN-indexes cannot be used for the '>' operator, so PG uses the ix_jobs_client_times btree-index and bigmap-ANDs the result.

 

Can you post you complete schema?

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