Have you try of excluding not null from index? Can you give dispersion of archivestatus?
06.05.2021, 21:59, "Semen Yefimenko" <semen.yefimenko@xxxxxxxxx>:
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, .. , column54Workers Planned: 2Workers Launched: 2Buffers: 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, .. , column54Sort Key: logtable.timestampcol DESCSort Method: quicksort Memory: 64730kBWorker 0: Sort Method: quicksort Memory: 55742kBWorker 1: Sort Method: quicksort Memory: 55565kBBuffers: shared hit=179817 read=115290Worker 0: actual time=7231.774..7458.703 rows=161723 loops=1Buffers: shared hit=55925 read=36265Worker 1: actual time=7217.856..7425.754 rows=161990 loops=1Buffers: 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, .. , column54Recheck Cond: ((logtable.entrytype = 4000) OR (logtable.entrytype = 4001) OR (logtable.entrytype = 4002))Filter: (logtable.archivestatus <= 1)Heap Blocks: exact=109146Buffers: shared hit=179803 read=115290Worker 0: actual time=1049.875..6809.231 rows=161723 loops=1Buffers: shared hit=55918 read=36265Worker 1: actual time=1035.156..6788.037 rows=161990 loops=1Buffers: 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=579Settings: random_page_cost = '1', search_path = '"$user", schema, public', temp_buffers = '80MB', work_mem = '1GB'Planning Time: 0.810 msExecution 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, .. , column54Workers Planned: 2Workers Launched: 2Buffers: 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, .. , column54Sort Key: logtable.timestampcol DESCSort Method: quicksort Memory: 71565kBWorker 0: Sort Method: quicksort Memory: 52916kBWorker 1: Sort Method: quicksort Memory: 51556kBBuffers: shared hit=147334 read=147776Worker 0: actual time=2771.975..2948.928 rows=153292 loops=1Buffers: shared hit=43227 read=43808Worker 1: actual time=2767.752..2938.688 rows=148424 loops=1Buffers: 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, .. , column54Recheck Cond: ((logtable.entrytype = 4000) OR (logtable.entrytype = 4001) OR (logtable.entrytype = 4002))Filter: (logtable.archivestatus <= 1)Heap Blocks: exact=122495Buffers: shared hit=147320 read=147776Worker 0: actual time=227.701..2408.580 rows=153292 loops=1Buffers: shared hit=43220 read=43808Worker 1: actual time=225.996..2408.705 rows=148424 loops=1Buffers: 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=580Settings: random_page_cost = '1', search_path = '"$user", schema, public', temp_buffers = '80MB', work_mem = '1GB'Planning Time: 0.609 msExecution Time: 4984.490 msI 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@xxxxxxxxx>:On 05/06/21 21:15, Alexey M Boltenkov wrote:
On 05/06/21 19:11, luis.roberto@xxxxxxxxxxxxxxx wrote:
----- Mensagem original -----De: "Semen Yefimenko" <semen.yefimenko@xxxxxxxxx> Para: "pgsql-performance" <pgsql-performance@xxxxxxxxxxxxxxxxxxxx> Enviadas: Quinta-feira, 6 de maio de 2021 11:38:39 Assunto: Very slow Query compared to Oracle / SQL - ServerSELECT 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. WeckThe 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;
