On 05/06/21 22:58, Alexey M Boltenkov wrote:
> Have you try of excluding not null from index? Can you give dispersion
> of archivestatus?
>
>
> 06.05.2021, 21:59, "Semen Yefimenko" <semen(dot)yefimenko(at)gmail(dot)com>:
>
> Yes, rewriting the query with an IN clause was also my first
> approach, but I didn't help much.
> The Query plan did change a little bit but the performance was not
> impacted.
>
> CREATE INDEX idx_arcstatus_le1 ON schema.logtable (
> archivestatus ) where (archivestatus <= 1)
> ANALYZE schema.logtable
>
>
> This resulted in this query plan:
>
> Gather Merge (cost=344618.96..394086.05 rows=423974
> width=2549) (actual time=7327.777..9142.358 rows=516031 loops=1)
> Output: column1, .. , column54
> Workers Planned: 2
> Workers Launched: 2
> Buffers: shared hit=179817 read=115290
> -> Sort (cost=343618.94..344148.91 rows=211987 width=2549)
> (actual time=7258.314..7476.733 rows=172010 loops=3)
> Output: column1, .. , column54
> Sort Key: logtable.timestampcol DESC
> Sort Method: quicksort Memory: 64730kB
> Worker 0: Sort Method: quicksort Memory: 55742kB
> Worker 1: Sort Method: quicksort Memory: 55565kB
> Buffers: shared hit=179817 read=115290
> Worker 0: actual time=7231.774..7458.703 rows=161723
> loops=1
> Buffers: shared hit=55925 read=36265
> Worker 1: actual time=7217.856..7425.754 rows=161990
> loops=1
> Buffers: shared hit=56197 read=36242
> -> Parallel Bitmap Heap Scan on schema.logtable
> (cost=5586.50..324864.86 rows=211987 width=2549) (actual
> time=1073.266..6805.850 rows=172010 loops=3)
> Output: column1, .. , column54
> Recheck Cond: ((logtable.entrytype = 4000) OR
> (logtable.entrytype = 4001) OR (logtable.entrytype = 4002))
> Filter: (logtable.archivestatus <= 1)
> Heap Blocks: exact=109146
> Buffers: shared hit=179803 read=115290
> Worker 0: actual time=1049.875..6809.231
> rows=161723 loops=1
> Buffers: shared hit=55918 read=36265
> Worker 1: actual time=1035.156..6788.037
> rows=161990 loops=1
> Buffers: shared hit=56190 read=36242
> -> BitmapOr (cost=5586.50..5586.50 rows=514483
> width=0) (actual time=945.179..945.179 rows=0 loops=1)
> Buffers: shared hit=3 read=1329
> -> Bitmap Index Scan on idx_entrytype
> (cost=0.00..738.13 rows=72893 width=0) (actual
> time=147.915..147.916 rows=65970 loops=1)
> Index Cond: (logtable.entrytype = 4000)
> Buffers: shared hit=1 read=171
> -> Bitmap Index Scan on idx_entrytype
> (cost=0.00..2326.17 rows=229965 width=0) (actual
> time=473.450..473.451 rows=225040 loops=1)
> Index Cond: (logtable.entrytype = 4001)
> Buffers: shared hit=1 read=579
> -> Bitmap Index Scan on idx_entrytype
> (cost=0.00..2140.61 rows=211624 width=0) (actual
> time=323.801..323.802 rows=225021 loops=1)
> Index Cond: (logtable.entrytype = 4002)
> Buffers: shared hit=1 read=579
> Settings: random_page_cost = '1', search_path = '"$user",
> schema, public', temp_buffers = '80MB', work_mem = '1GB'
> Planning Time: 0.810 ms
> Execution Time: 9647.406 ms
>
>
> seemingly faster.
> After doing a few selects, I reran ANALYZE:
> Now it's even faster, probably due to cache and other mechanisms.
>
> Gather Merge (cost=342639.19..391676.44 rows=420290
> width=2542) (actual time=2944.803..4534.725 rows=516035 loops=1)
> Output: column1, .. , column54
> Workers Planned: 2
> Workers Launched: 2
> Buffers: shared hit=147334 read=147776
> -> Sort (cost=341639.16..342164.53 rows=210145 width=2542)
> (actual time=2827.256..3013.960 rows=172012 loops=3)
> Output: column1, .. , column54
> Sort Key: logtable.timestampcol DESC
> Sort Method: quicksort Memory: 71565kB
> Worker 0: Sort Method: quicksort Memory: 52916kB
> Worker 1: Sort Method: quicksort Memory: 51556kB
> Buffers: shared hit=147334 read=147776
> Worker 0: actual time=2771.975..2948.928 rows=153292
> loops=1
> Buffers: shared hit=43227 read=43808
> Worker 1: actual time=2767.752..2938.688 rows=148424
> loops=1
> Buffers: shared hit=42246 read=42002
> -> Parallel Bitmap Heap Scan on schema.logtable
> (cost=5537.95..323061.27 rows=210145 width=2542) (actual
> time=276.401..2418.925 rows=172012 loops=3)
> Output: column1, .. , column54
> Recheck Cond: ((logtable.entrytype = 4000) OR
> (logtable.entrytype = 4001) OR (logtable.entrytype = 4002))
> Filter: (logtable.archivestatus <= 1)
> Heap Blocks: exact=122495
> Buffers: shared hit=147320 read=147776
> Worker 0: actual time=227.701..2408.580
> rows=153292 loops=1
> Buffers: shared hit=43220 read=43808
> Worker 1: actual time=225.996..2408.705
> rows=148424 loops=1
> Buffers: shared hit=42239 read=42002
> -> BitmapOr (cost=5537.95..5537.95 rows=509918
> width=0) (actual time=203.940..203.941 rows=0 loops=1)
> Buffers: shared hit=1332
> -> Bitmap Index Scan on idx_entrytype
> (cost=0.00..680.48 rows=67206 width=0) (actual
> time=31.155..31.156 rows=65970 loops=1)
> Index Cond: (logtable.entrytype = 4000)
> Buffers: shared hit=172
> -> Bitmap Index Scan on idx_entrytype
> (cost=0.00..2220.50 rows=219476 width=0) (actual
> time=112.459..112.461 rows=225042 loops=1)
> Index Cond: (logtable.entrytype = 4001)
> Buffers: shared hit=580
> -> Bitmap Index Scan on idx_entrytype
> (cost=0.00..2258.70 rows=223236 width=0) (actual
> time=60.313..60.314 rows=225023 loops=1)
> Index Cond: (logtable.entrytype = 4002)
> Buffers: shared hit=580
> Settings: random_page_cost = '1', search_path = '"$user",
> schema, public', temp_buffers = '80MB', work_mem = '1GB'
> Planning Time: 0.609 ms
> Execution Time: 4984.490 ms
>
> I don't see the new index used but it seems it's boosting the
> performance nevertheless.
> I kept the query, so I didn't rewrite the query to be WITHOUT nulls.
> Thank you already for the hint. What else can I do? With the
> current parameters, the query finishes in about 3.9-5.2 seconds
> which is already much better but still nowhere near the speeds of
> 280 ms in oracle.
> I would love to get it to at least 1 second.
>
>
> Am Do., 6. Mai 2021 um 20:20 Uhr schrieb Alexey M Boltenkov
> <padrebolt(at)yandex(dot)ru <mailto:padrebolt(at)yandex(dot)ru>>:
>
> On 05/06/21 21:15, Alexey M Boltenkov wrote:
>
> On 05/06/21 19:11, luis(dot)roberto(at)siscobra(dot)com(dot)br
> <mailto:luis(dot)roberto(at)siscobra(dot)com(dot)br> wrote:
>
> ----- Mensagem original -----
>
> De: "Semen Yefimenko"<semen(dot)yefimenko(at)gmail(dot)com>
> <mailto:semen(dot)yefimenko(at)gmail(dot)com>
> Para: "pgsql-performance"<pgsql-performance(at)lists(dot)postgresql(dot)org>
> <mailto:pgsql-performance(at)lists(dot)postgresql(dot)org>
> Enviadas: Quinta-feira, 6 de maio de 2021 11:38:39
> Assunto: Very slow Query compared to Oracle / SQL - Server
>
> SELECT column1,..., column54 where ((entrytype = 4000 or entrytype = 4001 or
> entrytype = 4002) and (archivestatus <= 1)) order by timestampcol desc;
>
>
>
> The first thing I would try is rewriting the query to:
>
> SELECT column1,..., column54
> FROM logtable
> WHERE (entrytype in (4000,4001,4002))
> AND (archivestatus <= 1))
> ORDER BY timestampcol DESC;
>
> Check if that makes a difference...
>
> Luis R. Weck
>
>
>
> The IN statement will probable result in just recheck
> condition change to entrytype = any('{a,b,c}'::int[]).
> Looks like dispersion of archivestatus is not enough to
> use index idx_arcstatus.
>
> Please try to create partial index with condition like
> (archivestatus <= 1) and rewrite select to use
> (archivestatus is not null and archivestatus <= 1).
>
> CREATE INDEX idx_arcstatus_le1 ON schema.logtable (
> archivestatus ) where (archivestatus <= 1) TABLESPACE
> tablespace;
>
> I'm sorry, 'archivestatus is not null' is only necessary for
> index without nulls.
>
>
> CREATE INDEX idx_arcstatus_le1 ON schema.logtable (
> archivestatus ) where (archivestatus is not null and
> archivestatus <= 1) TABLESPACE tablespace;
>
BTW, please try to reset random_page_cost.