Re: How to improve sql query to achieve the better plan

[Pavel Stehule <pavel.stehule@xxxxxxxxx>]

Hi

ne 30. 9. 2018 v 18:23 odesílatel Arup Rakshit <ar@xxxxxxx> napsal:

I have the below query which is taking 1873 ms. How can I improve this?

explain analyze select

sum(coalesce(price_cents, 0)::bigint * coalesce(quantity, 0) * (1 - coalesce(workitems.discount, 0)/ 100)) as total_budget_cents,

sum(coalesce(price_cents, 0)::bigint * coalesce(quantity, 0) * (1 - coalesce(workitems.discount, 0)/ 100) + coalesce(additional_cost_cents, 0) - coalesce(cost_reduction_cents, 0)) as final_budget_cents,

projects.id as project_id

from

projects

left join workitems on

workitems.project_id = projects.id

where

workitems.deleted_at is null

group by

projects.id

order by

project_id asc

And explain output is:

Sort  (cost=62851.33..62856.07 rows=1897 width=35) (actual time=1872.867..1873.003 rows=1229 loops=1)

  Sort Key: projects.id

  Sort Method: quicksort  Memory: 145kB

  ->  HashAggregate  (cost=62719.59..62748.04 rows=1897 width=35) (actual time=1871.281..1872.104 rows=1229 loops=1)

        Group Key: projects.id

        ->  Hash Right Join  (cost=159.68..45386.32 rows=364911 width=35) (actual time=2.226..637.936 rows=365784 loops=1)

              Hash Cond: (workitems.project_id = projects.id)

              Filter: (workitems.deleted_at IS NULL)

              Rows Removed by Filter: 257457

              ->  Seq Scan on workitems  (cost=0.00..36655.53 rows=623353 width=43) (actual time=0.020..220.215 rows=623175 loops=1)

              ->  Hash  (cost=135.97..135.97 rows=1897 width=16) (actual time=2.177..2.177 rows=1897 loops=1)

                    Buckets: 2048  Batches: 1  Memory Usage: 105kB

                    ->  Seq Scan on projects  (cost=0.00..135.97 rows=1897 width=16) (actual time=0.013..1.451 rows=1897 loops=1)

Planning time: 2.775 ms

Execution time: 1873.308 ms

maybe conditional index can help

CREATE INDEX ON workitems(project_id) WHERE deleted_at is null

Regards

Pavel

Projects table has the index:

Indexes:

    "projects_pkey" PRIMARY KEY, btree (id)

    "index_projects_on_company_id" btree (company_id)

    "index_projects_on_deleted_at" btree (deleted_at)

    "index_projects_on_inspector_id" btree (inspector_id)

    "index_projects_on_managed_offline_by_user_id" btree (managed_offline_by_user_id)

    "index_projects_on_project_status_id" btree (project_status_id)

    "index_projects_on_shipyard_id" btree (shipyard_id)

    "index_projects_on_vessel_id" btree (vessel_id)

Workitems table has the index:

Indexes:

    "workitems_pkey" PRIMARY KEY, btree (id)

    "index_workitems_on_company_id" btree (company_id)

    "index_workitems_on_deleted_at" btree (deleted_at)

    "index_workitems_on_parent_workitem_id" btree (parent_workitem_id)

    "index_workitems_on_project_id" btree (project_id)

    "index_workitems_on_standard_workitem_id" btree (standard_workitem_id)

    "index_workitems_on_workitem_category_id" btree (workitem_category_id)

Thanks,

Arup Rakshit

ar@xxxxxxx