Re: Trigram is slow when 10m rows - Mailing list pgsql-general
| From | Oleg Bartunov |
|---|---|
| Subject | Re: Trigram is slow when 10m rows |
| Date | |
| Msg-id | CAF4Au4wGcFynSqS2hXNkh53zG=U06Dy_Nw8eJV3Rk72Oqbwzgg@mail.gmail.com Whole thread Raw |
| In response to | Re: Trigram is slow when 10m rows (Aaron Lewis <the.warl0ck.1989@gmail.com>) |
| List | pgsql-general |
On Sun, Nov 13, 2016 at 5:25 PM, Aaron Lewis <the.warl0ck.1989@gmail.com> wrote:
Thanks Oleg.
I've increased work_mem to 128MB, now the query falls down to 1.7s,
faster but still not good enough.
Is there any other thing I can do about it?
your query 'x264' is short in terms of the number of trigrams, so trigram index isn't good. Did you tried text_pattern_ops for btree ? Something like
create index title_btree_idx on mytable using btree(title text_pattern_ops );
test=# explain analyze select * from mytable where title ilike 'x264';
QUERY PLAN
------------------------------------------------------------ ------------------------------ ------------------------------ --------------
Bitmap Heap Scan on mytable (cost=462.69..5639.67 rows=1380
width=83) (actual time=1754.656..1754.656 rows=0 loops=1)
Recheck Cond: (title ~~* 'x264'::text)
Rows Removed by Index Recheck: 1220793
Heap Blocks: exact=197567
-> Bitmap Index Scan on title_trgm_idx (cost=0.00..462.35
rows=1380 width=0) (actual time=346.663..346.663 rows=1220793 loops=1)
Index Cond: (title ~~* 'x264'::text)
Planning time: 1.168 ms
Execution time: 1755.944 ms
On Sun, Nov 13, 2016 at 10:04 PM, Oleg Bartunov <obartunov@gmail.com> wrote:
>
>
> On Sun, Nov 13, 2016 at 2:54 PM, Aaron Lewis <the.warl0ck.1989@gmail.com>
> wrote:
>>
>> I have a simple table with Trigram index,
>>
>> create table mytable(hash char(40), title text);
>> create index title_trgm_idx on mytable using gin(title gin_trgm_ops);
>>
>> When I run a query with 10m rows, it uses the Trigram index, but takes
>> 3s to execute, very slow.
>> (I have 80m rows, but only inserted 10m for testing purpose)
>>
>> test=# select count(*) from mytable;
>> count
>> ----------
>> 13971887
>> (1 row)
>>
>> test=# explain analyze select * from mytable where title ilike 'x264';
>> QUERY PLAN
>>
>> ------------------------------------------------------------ ------------------------------ ------------------------------ --------------
>> Bitmap Heap Scan on mytable (cost=462.69..5639.67 rows=1380
>> width=83) (actual time=2937.308..2937.308 rows=0 loops=1)
>> Recheck Cond: (title ~~* 'x264'::text)
>> Rows Removed by Index Recheck: 11402855
>> Heap Blocks: exact=39557 lossy=158010
>> -> Bitmap Index Scan on title_trgm_idx (cost=0.00..462.35
>> rows=1380 width=0) (actual time=342.440..342.440 rows=1220793 loops=1)
>> Index Cond: (title ~~* 'x264'::text)
>> Planning time: 0.611 ms
>> Execution time: 2937.729 ms
>> (8 rows)
>>
>> Any ideas to speed things up?
>
>
> Rows Removed by Index Recheck: 11402855
> Heap Blocks: exact=39557 lossy=158010
>
> You need to increase work_mem
>>
>>
>> --
>> Best Regards,
>> Aaron Lewis - PGP: 0x13714D33 - http://pgp.mit.edu/
>> Finger Print: 9F67 391B B770 8FF6 99DC D92D 87F6 2602 1371 4D33
>>
>>
>> --
>> Sent via pgsql-general mailing list (pgsql-general@postgresql.org)
>> To make changes to your subscription:
>> http://www.postgresql.org/mailpref/pgsql-general
>
>
--
Best Regards,
Aaron Lewis - PGP: 0x13714D33 - http://pgp.mit.edu/
Finger Print: 9F67 391B B770 8FF6 99DC D92D 87F6 2602 1371 4D33
pgsql-general by date: