sql - Postgres 查询需要更长的时间来执行

select (20 columns from table A,1 from table B) from A a LEFT JOIN B b on a.b_id = b.id LEFT JOIN C c on a.c_id = c.id LEFT JOIN D d on a.d_id = d.id order by a.c_id desc

Sort (cost=1698494.81..1699762.99 rows=507272 width=227) (actual time=1547526.027..1547674.093 rows=20206 loops=1) Output: (21 columns) Sort Key: a.c_id DESC Sort Method: external sort Disk: 3712kB Buffers: shared hit=62533, temp read=464 written=464 -> Nested Loop Left Join (cost=0.85..1539453.70 rows=507272 width=227) (actual time=159.128..1547216.092 rows=20206 loops=1) Output: (21 columns) Join Filter: (o.d_id = d.id) Rows Removed by Join Filter: 101454326 Buffers: shared hit=62530 -> Nested Loop Left Join (cost=0.85..14931.69 rows=20206 width=206) (actual time=0.085..2392.023 rows=20206 loops=1) Output: (21 columns) Buffers: shared hit=61914 -> Nested Loop Left Join (cost=0.57..7601.31 rows=20206 width=178) (actual time=0.057..1040.248 rows=20206 loops=1) Output: (21 columns) Buffers: shared hit=1326 -> Index Scan using A_pkey on public.A a (cost=0.29..1149.45 rows=20206 width=146) (actual time=0.027..263.851 rows=20206 loops=1) Output: (24 A columns) Buffers: shared hit=798 -> Index Scan using B_pkey on public.B b (cost=0.28..0.31 rows=1 width=36) (actual time=0.009..0.009 rows=0 loops=20206) Output: (3 B columns) Index Cond: (a.b_id = b.id) Buffers: shared hit=528 -> Index Scan using C_pkey on public.C c (cost=0.29..0.35 rows=1 width=36) (actual time=0.023..0.035 rows=1 loops=20206) Output: (22 C columns) Index Cond: (a.c_id = c.id) Buffers: shared hit=60588 -> Materialize (cost=0.00..183.31 rows=5021 width=0) (actual time=0.008..36.691 rows=5021 loops=20206) Buffers: shared hit=108 -> Seq Scan on public.D d (cost=0.00..158.21 rows=5021 width=0) (actual time=0.013..39.429 rows=5021 loops=1) Buffers: shared hit=108 Planning time: 1.264 ms Execution time: 1547818.586 ms

Sort (cost=1646680.72..1647870.39 rows=475870 width=360) (actual time=37209.363..37212.636 rows=20097 loops=1) Output: ( 21 columns) Sort Key: a.c_id DESC Sort Method: external merge Disk: 6488kB Buffers: shared hit=186244 read=15850, temp read=811 written=813 -> Nested Loop Left Join (cost=1.14..1445656.68 rows=475870 width=360) (actual time=24.864..37136.111 rows=20097 loops=1) Output: ( 21 columns) Join Filter: (d.id = a.d_id) Rows Removed by Join Filter: 122270148 Buffers: shared hit=186241 read=15850 -> Nested Loop Left Join (cost=0.85..15382.43 rows=16552 width=412) (actual time=6.398..483.632 rows=20097 loops=1) Output: ( 21 columns) Inner Unique: true Buffers: shared hit=130359 read=181 -> Nested Loop Left Join (cost=0.57..9035.64 rows=16552 width=391) (actual time=4.798..249.724 rows=20097 loops=1) Output: ( 21 columns) Inner Unique: true Buffers: shared hit=70148 read=101 -> Index Scan using A_pkey on public.A a (cost=0.29..3882.13 rows=16552 width=359) (actual time=2.297..55.077 rows=20097 loops=1) Output: (24 A columns) Buffers: shared hit=10013 read=71 -> Index Scan using B_pkey on public.B b (cost=0.28..0.31 rows=1 width=36) (actual time=0.006..0.006 rows=1 loops=20097) Output: (3 B columns) Index Cond: (a.b_id = b.id) Buffers: shared hit=60135 read=30 -> Index Scan using C_pkey on public.C c (cost=0.29..0.38 rows=1 width=29) (actual time=0.010..0.010 rows=1 loops=20097) Output: (22 C columns) Index Cond: (o.created_by_2 = ur.id) Buffers: shared hit=60211 read=80 -> Materialize (cost=0.28..299.28 rows=5750 width=0) (actual time=0.000..0.376 rows=6084 loops=20097) Buffers: shared hit=313 read=44 -> Index Only Scan using D_pkey on public.D d (cost=0.28..270.53 rows=5750 width=0) (actual time=2.452..13.493 rows=6084 loops=1) Heap Fetches: 1032 Buffers: shared hit=313 read=44 Planning time: 1.071 ms Execution time: 37214.718 ms