>
> With those sizes, the gin index will probably be naturally kept mostly
> in the file-system cache, if it is used regularly. So the original
> slowness of your first query is likely just a cold-cache problem. Can
> you generate a stream of realistic queries and see what it stabilizes
> at?
>
>
> > I just wanted to understand why the GIN index is not working, but it
> works
> > here:
> https://www.depesz.com/2011/02/19/waiting-for-9-1-faster-likeilike/
>
> In your first email, the gin index did "work", according to the
> execution plan. It just wasn't as fast as you wanted. In general,
> the longer the query string is between the %%, the worse it will
> perform (until version 9.6, and to a smaller degree even with 9.6).
> But it still seems oddly slow to me, unless you have a cold-cache and
> really bad (or overloaded) IO.
>
> >
> >>
> >>
> >> It would be interesting to see the output of explain (analyze,
> >> buffers) with track_io_timing turned on.
> >
> >
> > explain analyze buffer with track_io_timing turned on:
> ...
>
> That is the wrong query. The CTE (i.e. the WITH part) is an
> optimization fence, so it can't use the gin index, simply because of
> the way you query is written. (I think Melvin suggested it because he
> noticed that using the gin index actually slowed down the query, so he
> wanted to force it to not be used.)
>
Oh ok.
- Here is the explain analyze buffer with the original query I posted here
with the gin index:
Query:
> explain (analyze, buffers)
> SELECT 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=390.07..390.08 rows=1 width=20) (actual
> time=3945.263..3945.280 rows=4 loops=1)
> Buffers: shared hit=5956 read=10
> I/O Timings: read=60.323
> -> Sort (cost=390.07..390.08 rows=1 width=20) (actual
> time=3945.256..3945.260 rows=4 loops=1)
> Sort Key: "title"
> Sort Method: quicksort Memory: 25kB
> Buffers: shared hit=5956 read=10
> I/O Timings: read=60.323
> -> Bitmap Heap Scan on "ja_jobs" (cost=386.05..390.06 rows=1
> width=20) (actual time=3944.857..3945.127 rows=4 loops=1)
> Recheck Cond: (("clientid" = 31239) AND ("time_job" >
> 1457826264) AND (("title")::"text" ~~* '% WER%'::"text"))
> Buffers: shared hit=5951 read=10
> I/O Timings: read=60.323
> -> BitmapAnd (cost=386.05..386.05 rows=1 width=0) (actual
> time=3929.540..3929.540 rows=0 loops=1)
> Buffers: shared hit=5950 read=7
> I/O Timings: read=45.021
> -> Bitmap Index Scan on "ix_jobs_client_times"
> (cost=0.00..50.16 rows=1660 width=0) (actual time=45.536..45.536 rows=795
> loops=1)
> Index Cond: (("clientid" = 31239) AND
> ("time_job" > 1457826264))
> Buffers: shared hit=5 read=7
> I/O Timings: read=45.021
> -> Bitmap Index Scan on "ix_jobs_trgm_gin"
> (cost=0.00..335.64 rows=485 width=0) (actual time=3883.886..3883.886
> rows=32 loops=1)
> Index Cond: (("title")::"text" ~~* '%RYAN WER
> %'::"text")
> Buffers: shared hit=5945
> Total runtime: 3945.554 ms
