When I use postgres and issue a simple sequential scan for a table inventory using query "select * from inventory;", I can see from "top" that postmaster is using 100% CPU, which limits the query execution time. My question is that, why CPU is the bottleneck here and what is postmaster doing? Is there any way to improve the performance? Thanks!
PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND 15401 postgres 20 0 4371m 517m 515m R 99.8 3.2 0:30.14 postmaster
Query: select * from inventory;
explain analyze select * from inventory; QUERY PLAN
-------------------------------------------------------------------------------------------------------------- ------------ Seq Scan on inventory (cost=0.00..180937.00 rows=11745000 width=16) (actual time=0.005..1030.403 rows=117450 00 loops=1) Total runtime: 1750.889 ms (2 rows)
Table "public.inventory" Column | Type | Modifiers ----------------------+---------+----------- inv_date_sk | integer | not null inv_item_sk | integer | not null inv_warehouse_sk | integer | not null inv_quantity_on_hand | integer | Indexes: "inventory_pkey" PRIMARY KEY, btree (inv_date_sk, inv_item_sk, inv_warehouse_sk)
