Hi Albe, Thank you so much for information, will check this and get back to you if any help required.
I have a doubt why didn't the parallelism works here ,could u plz guide me? Thank you so much again. On Thu, 11 Feb, 2021, 1:23 PM Laurenz Albe, <laurenz.a...@cybertec.at> wrote: > On Thu, 2021-02-11 at 05:09 +0530, Brajendra Pratap wrote: > > I am unable to execute the below in parallel plz suggest how can I > achieve parallelism here. > > > > select count(*) over () VIEWALLROWCOUNT,abc.*,ROW_NUMBER() OVER (order > by trn_transaction_date desc ) AS RowNumber from ( > > select * from transactions where trn_store_date_id=20201202) abc; > > > > Query plan is as mentioned below :- > > > > explain analyze select count(*) over () > VIEWALLROWCOUNT,abc.*,ROW_NUMBER() OVER (order by trn_transaction_date > desc ) AS RowNumber from ( > > select * from transactions where trn_store_date_id=20201218) abc; > > LOG: duration: 25820.176 ms statement: explain analyze select count(*) > over () VIEWALLROWCOUNT,abc.*,ROW_NUMBER() OVER (order by > trn_transaction_date desc ) AS RowNumber from ( > > select * from transactions where trn_store_date_id=20201218) abc; > > > QUERY PLAN > > > ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------ > > WindowAgg (cost=4474843.51..4498066.81 rows=774110 width=21297) > (actual time=21455.495..25241.738 rows=795190 loops=1) > > -> WindowAgg (cost=4474843.51..4488390.44 rows=774110 width=21289) > (actual time=10588.494..15311.865 rows=795190 loops=1) > > -> Sort (cost=4474843.51..4476778.79 rows=774110 width=21281) > (actual time=10588.422..11771.300 rows=795190 loops=1) > > Sort Key: transactions.trn_transaction_date DESC > > Sort Method: external merge Disk: 1496856kB > > -> Result (cost=0.00..270640.32 rows=774110 > width=21281) (actual time=0.117..4504.159 rows=795190 loops=1) > > -> Append (cost=0.00..262899.22 rows=774110 > width=21281) (actual time=0.094..1449.532 rows=795190 loops=1) > > -> Seq Scan on transactions > (cost=0.00..0.00 rows=1 width=47554) (actual time=0.019..0.019 rows=0 > loops=1) > > Filter: (trn_store_date_id = 20201218) > > -> Index Scan using > idx_202012_trn_store_date_id on transactions_202012 (cost=0.56..259028.67 > rows=774109 width=21281) (actual time=0.074..1357.764 rows=795190 loops=1) > > Index Cond: (trn_store_date_id = > 20201218) > > Planning Time: 116.472 ms > > Execution Time: 25676.098 ms > > > > Note :- We had tried different options like max_worker_processes, > max_parallel_workers, > max_parallel_workers_per_gather,max_parallel_maintenance_worker to execute > it in parallel but no luck. > > I don't think parallelization will help you here. > > Your problem is probably the "abc.*" in the SELECT list. > > There must be really large data in this table, so it takes a long time to > fetch and > sort the rows. Try selecting only the columns you need. > > Alternatively, add a LIMIT clause. Do you really need all 800000 rows? > > Yours, > Laurenz Albe > -- > Cybertec | https://www.cybertec-postgresql.com > >
