Hello!
We migrated a PgSQL database from Cloud SQL to compute engine and since
then there is a SQL we observed taking a long time. After some study, I
found that the SQL is using NESTED LOOP where the cost is too high. I tried
VACUUM FULL and ANALYZE, but to no avail. Only when I disabled the nested
loop (enable_nestloop) the query starts running normally.
I checked in the cloud SQL the nested loop is enabled, not sure why this
difference. Can anyone please assist.
Here is the execution plan (bad one):
----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Nested Loop (cost=120339.76..132772.17 rows=1 width=775) (actual
time=901159.223..901897.801 rows=12 loops=1)
Join Filter: (marketing_app_homecounsellinglead.id = w0.cancel_event_id)
Rows Removed by Join Filter: 28926
Buffers: shared hit=502303510 read=299 dirtied=1
-> Unique (cost=1.58..4283.42 rows=1 width=4) (actual
time=47.768..51.917 rows=13 loops=1)
Buffers: shared hit=9680 read=19
-> Nested Loop Semi Join (cost=1.58..4283.42 rows=1 width=4)
(actual time=47.767..51.900 rows=36 loops=1)
Buffers: shared hit=9680 read=19
-> Nested Loop (cost=1.00..4282.75 rows=1 width=8) (actual
time=46.703..51.596 rows=44 loops=1)
Buffers: shared hit=9379 read=19
-> Index Scan using marketing_a_cancel__55ffff_idx on
marketing_app_leadhistory w0 (cost=0.57..4274.30 rows=1 width=8) (actual
time=46.678..51.232 rows=44 loops=1)
Index Cond: ((cancel_event_id IS NOT NULL) AND
(cancel_event_type = 1))
Filter: ((status_id = 93) AND
((followup_date)::date >= '2024-08-01'::date) AND ((followup_date)::date <=
'2024-08-07'::date))
Rows Removed by Filter: 22268
Buffers: shared hit=9170 read=19
-> Index Scan using marketing_app_leadinfo_pkey on
marketing_app_leadinfo w1 (cost=0.43..8.45 rows=1 width=8) (actual
time=0.006..0.006 rows=1 loops=44)
Index Cond: (id = w0.lead_id)
Buffers: shared hit=209
-> Nested Loop Semi Join (cost=0.58..0.66 rows=1 width=12)
(actual time=0.006..0.006 rows=1 loops=44)
Join Filter: (v0_1.id = u0_2.id)
Buffers: shared hit=301
-> Index Only Scan using branch_id_idx on branch v0_1
(cost=0.14..0.16 rows=1 width=4) (actual time=0.001..0.002 rows=1 loops=44)
Index Cond: (id = w1.branch_id)
Heap Fetches: 44
Buffers: shared hit=88
-> Nested Loop (cost=0.43..0.49 rows=1 width=8)
(actual time=0.004..0.004 rows=1 loops=44)
Join Filter: (u0_2.id = u1_2.branch_id)
Buffers: shared hit=213
-> Index Only Scan using branch_id_idx on
branch u0_2 (cost=0.14..0.16 rows=1 width=4) (actual time=0.001..0.001
rows=1 loops=44)
Index Cond: (id = w1.branch_id)
Heap Fetches: 44
Buffers: shared hit=88
-> Index Only Scan using
"Employee_brancanh_employee_id_branch_id_06fcf064_uniq" on
authentication_employee_branch u1_2 (cost=0.29..0.31 rows=1 width=4)
(actual time=0.002..0.002 rows=1 loops=44)
Index Cond: ((employee_id = 43) AND
(branch_id = w1.branch_id))
Heap Fetches: 36
Buffers: shared hit=125
-> Hash Join (cost=120338.17..128483.90 rows=387 width=775) (actual
time=69312.677..69372.647 rows=2226 loops=13)
Hash Cond: (marketing_app_homecounsellinglead.lead_id =
marketing_app_leadinfo.id)
Buffers: shared hit=502293830 read=280 dirtied=1
-> Seq Scan on marketing_app_homecounsellinglead
(cost=0.00..7513.53 rows=167553 width=775) (actual time=0.003..19.903
rows=167589 loops=13)
Buffers: shared hit=75894
-> Hash (cost=119938.59..119938.59 rows=31967 width=4) (actual
time=901063.121..901063.129 rows=5138545 loops=1)
Buckets: 8388608 (originally 32768) Batches: 1 (originally
1) Memory Usage: 246188kB
Buffers: shared hit=502217936 read=280 dirtied=1
-> Nested Loop (cost=56.29..119938.59 rows=31967 width=4)
(actual time=0.271..899599.420 rows=5138545 loops=1)
Join Filter: (u0.id = marketing_app_leadinfo.branch_id)
Rows Removed by Join Filter: 713188839
Buffers: shared hit=502217936 read=280 dirtied=1
-> Nested Loop (cost=55.85..1005.32 rows=20
width=16) (actual time=0.237..35.473 rows=75208 loops=1)
Buffers: shared hit=272
-> Nested Loop Semi Join (cost=14.63..122.14
rows=20 width=4) (actual time=0.034..1.153 rows=553 loops=1)
Join Filter:
(marketing_app_contactsource.field_type_id = u0_1.id)
Rows Removed by Join Filter: 1090
Buffers: shared hit=194
-> Index Scan using
marketing_app_contactsource_pkey on marketing_app_contactsource
(cost=0.28..54.74 rows=550 width=8) (actual time=0.006..0.460 rows=553
loops=1)
Buffers: shared hit=189
-> Materialize (cost=14.36..26.16 rows=5
width=8) (actual time=0.000..0.000 rows=3 loops=553)
Buffers: shared hit=5
-> Hash Join (cost=14.36..26.14
rows=5 width=8) (actual time=0.023..0.032 rows=10 loops=1)
Hash Cond: (u0_1.id =
u1_1.fieldtype_id)
Buffers: shared hit=5
-> Seq Scan on
authentication_fieldtype u0_1 (cost=0.00..11.40 rows=140 width=4) (actual
time=0.004..0.006 rows=10 loops=1)
Buffers: shared hit=1
-> Hash (cost=14.29..14.29
rows=5 width=4) (actual time=0.014..0.015 rows=10 loops=1)
Buckets: 1024 Batches:
1 Memory Usage: 9kB
Buffers: shared hit=4
-> Index Only Scan
using authentication_employee__employee_id_fieldtype_id_a490d886_uniq on
authentication_employee_field_type u1_1 (cost
=0.29..14.29 rows=5 width=4) (actual time=0.009..0.012 rows=10 loops=1)
Index Cond:
(employee_id = 43)
Heap Fetches: 10
Buffers: shared
hit=4
-> HashAggregate (cost=41.22..42.69 rows=147
width=12) (actual time=0.001..0.042 rows=136 loops=553)
Group Key: v0.id
Batches: 1 Memory Usage: 40kB
Buffers: shared hit=78
-> Hash Semi Join (cost=29.97..40.85
rows=147 width=12) (actual time=0.136..0.176 rows=136 loops=1)
Hash Cond: (v0.id = u0.id)
Buffers: shared hit=78
-> Seq Scan on branch v0
(cost=0.00..8.78 rows=178 width=4) (actual time=0.003..0.015 rows=178
loops=1)
Buffers: shared hit=7
-> Hash (cost=28.13..28.13
rows=147 width=8) (actual time=0.129..0.132 rows=136 loops=1)
Buckets: 1024 Batches: 1
Memory Usage: 14kB
Buffers: shared hit=71
-> Hash Join
(cost=18.87..28.13 rows=147 width=8) (actual time=0.069..0.118 rows=136
loops=1)
Hash Cond: (u0.id =
u1.branch_id)
Buffers: shared hit=71
-> Seq Scan on branch
u0 (cost=0.00..8.78 rows=178 width=4) (actual time=0.002..0.026 rows=178
loops=1)
Buffers: shared
hit=7
-> Hash
(cost=17.03..17.03 rows=147 width=4) (actual time=0.063..0.064 rows=136
loops=1)
Buckets: 1024
Batches: 1 Memory Usage: 13kB
Buffers: shared
hit=64
-> Index Only
Scan using "Employee_brancanh_employee_id_branch_id_06fcf064_uniq" on
authentication_employee_branch u1 (cost=0.29..1
7.03 rows=147 width=4) (actual time=0.008..0.050 rows=136 loops=1)
Index Cond:
(employee_id = 43)
Heap
Fetches: 122
Buffers:
shared hit=64
-> Index Scan using
marketing_app_leadinfo_contact_source_id_b9ffb703 on marketing_app_leadinfo
(cost=0.43..5632.63 rows=25123 width=12) (actual time=0.354..10.980 row
s=9551 loops=75208)
Index Cond: (contact_source_id =
marketing_app_contactsource.id)
Filter: ((academic_year)::text = '2024-25'::text)
Rows Removed by Filter: 15269
Buffers: shared hit=502217664 read=280 dirtied=1
Planning:
Buffers: shared hit=163
Planning Time: 2.082 ms
JIT:
Functions: 84
Options: Inlining false, Optimization false, Expressions true, Deforming
true
Timing: Generation 5.327 ms, Inlining 0.000 ms, Optimization 1.802 ms,
Emission 37.293 ms, Total 44.422 ms
Execution Time: 901926.050 ms
(107 rows)
