PostgreSQL查询的执行时间很慢

Question

I did the explain analyze for this query, it was giving 30ms, but if the data is more I will get an execution expired; Using PostgreSQL 10

For normal execution: https://explain.depesz.com/s/gSPP

For slow execution: https://explain.depesz.com/s/bQN2

SELECT inventory_histories.*, order_items.order_id as order_id FROM
"inventory_histories" LEFT JOIN order_items ON (order_items.id = 
inventory_histories.reference_id AND inventory_histories.reference_type = 4) 
WHERE "inventory_histories"."inventory_id" = 1313 AND 
(inventory_histories.location_id = 15) ORDER BY inventory_histories.id DESC 
LIMIT 10 OFFSET 0;

Indexes:

"inventory_histories_pkey" PRIMARY KEY, btree (id)
"inventory_histories_created_at_index" btree (created_at)
"inventory_histories_inventory_id_index" btree (inventory_id)
"inventory_histories_location_id_index" btree (location_id)

Answer 1

For this query:

SELECT ih.*, oi.order_id as order_id
FROM "inventory_histories" ih LEFT JOIN
     order_items oi
     ON oi.id = ih.reference_id AND
        ih.reference_type = 4 
WHERE ih."inventory_id" = 1313 AND 
      ih.location_id = 15
ORDER BY ih.id DESC 
LIMIT 10 OFFSET 0;

For this query, you want composite indexes on inventory_histories(inventory_id, location_id, id, reference_id) and on order_items(id, reference_type, order_id) .