Re: Query performance issue

Hi Mechel,
I added the index as you suggested and the planner going through the bitmap index scan,heap and the new planner is,HaOx | explain.depesz.com

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HaOx | explain.depesz.com

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Mem config: 
Aurora PostgreSQL 11.7 on x86_64-pc-linux-gnu, compiled by gcc (GCC) 4.9.3, 64-bit
vCPU = 64RAM = 512show shared_buffers = 355 GBshow work_mem = 214 MB
show maintenance_work_mem = 8363MBshow effective_cache_size = 355 GB

Thanks,Rj
On Friday, September 4, 2020, 02:55:50 PM PDT, Michael Lewis <mlewis(at)entrata(dot)com> wrote:

"Subquery Scan on rec (cost=1628601.89..1676580.92 rows=7381 width=41) (actual time=22171.986..23549.079 rows=1236042 loops=1)"" Filter: (rec.mpos = 1)"" Rows Removed by Filter: 228737"" Buffers: shared hit=45 read=1166951"" I/O Timings: read=29.530"" -> WindowAgg (cost=1628601.89..1658127.45 rows=1476278 width=49) (actual time=22171.983..23379.219 rows=1464779 loops=1)"" Buffers: shared hit=45 read=1166951"" I/O Timings: read=29.530"" -> Sort (cost=1628601.89..1632292.58 rows=1476278 width=41) (actual time=22171.963..22484.044 rows=1464779 loops=1)"" Sort Key: receiving_item_delivered_received.serial_no, receiving_item_delivered_received.eventtime DESC"" Sort Method: quicksort Memory: 163589kB"" Buffers: shared hit=45 read=1166951"" I/O Timings: read=29.530"" -> Gather (cost=1000.00..1477331.13 rows=1476278 width=41) (actual time=1.296..10428.060 rows=1464779 loops=1)"" Workers Planned: 2"" Workers Launched: 2"" Buffers: shared hit=39 read=1166951"" I/O Timings: read=29.530"" -> Parallel Seq Scan on receiving_item_delivered_received (cost=0.00..1328703.33 rows=615116 width=41) (actual time=1.262..10150.325 rows=488260 loops=3)"" Filter: (((COALESCE(serial_no, ''::character varying))::text <> ''::text) AND ((eventtype)::text = 'LineItemdetailsReceived'::text) AND ((replenishmenttype)::text = 'DC2SWARRANTY'::text))"" Rows Removed by Filter: 6906258"" Buffers: shared hit=39 read=1166951"" I/O Timings: read=29.530""Planning Time: 0.375 ms""Execution Time: 23617.348 ms"

That is doing a lot of reading from disk. What do you have shared_buffers set to? I'd expect better cache hits unless it is quite low or this is a query that differs greatly from the typical work.
Also, did you try adding the index I suggested? That lowest node has 488k rows coming out of it after throwing away 6.9 million. I would expect an index on only eventtype, replenishmenttype to be quite helpful. I don't assume you have tons of rows where serial_no is null.