Hi, On Tue, Jul 23, 2019 at 3:29 PM Alexander Voytsekhovskyy <young.inbox@xxxxxxxxx> wrote: > > I have quite complicated query: > > SELECT axis_x1, axis_y1, SUM(delivery_price) as v_1 FROM ( > SELECT to_char(delivery_data.delivery_date, 'YYYY-MM') as axis_x1, clients.id_client as axis_y1, delivery_data.amount * production_price.price * groups.discount as delivery_price > > FROM delivery_data > JOIN client_tt ON (client_tt.id_client_tt = delivery_data.id_client_tt) > JOIN clients ON (client_tt.id_client = clients.id_client) > JOIN production ON (production.id = delivery_data.id_product) > JOIN groups ON (groups.id = delivery_data.delivery_group_id AND client_tt.id_group = groups.id AND groups.id = clients.id_group) > LEFT JOIN production_price on (delivery_data.id_product = production_price.id_production AND groups.price_list_id = production_price.price_list_id AND delivery_data.delivery_date BETWEEN production_price.date_from AND production_price.date_to) > > WHERE delivery_data.delivery_date between '2019-03-01' AND '2019-06-30' > AND delivery_data.delivery_group_id IN (...short list of values...) > AND delivery_data.id_product IN ()) AS tmpsource > > WHERE TRUE > GROUP BY GROUPING SETS ((axis_x1, axis_y1), (axis_x1), (axis_y1), ()) > > It runs well, took 1s and returns 4000 rows. > > You can see explain analyze verbose here: > https://explain.depesz.com/s/AEWj > > The problem is, when i wrap it to > > A) > INSERT INTO norepl_1542_result (axis_x1, axis_y1, v_1) > SELECT .... SAME QUERY > > OR even > > B) > WITH rows AS ( > ... SAME SELECT QUERY ... > ) > INSERT INTO norepl_1542_result (axis_x1, axis_y1, v_1) > SELECT * FROM rows > > The query time dramatically drops to 500+ seconds. > > You can see explain analyze verbose here > https://explain.depesz.com/s/AEWj > > As you can see, 100% of time goes to same SELECT query, there is no issues with INSERT-part > > I have played a lot and it's reproducing all time. > > So my question is, why wrapping SELECT query with INSERT FROM SELECT dramatically change query plan and make it 500x slower? Which version of PostgreSQL do you have? Which OS does it running on? Thank you.
