Postgresql shows slow query but low execution time in analyzed output - postgresql

Question

Postgresql Version: 13.6
Server size: 2cx4g
Logs of Postgresql shows duration 6215.926ms, but explain shows that the execution time and planning time are less than 200ms
Is slow reading speed of the client a cause of the problem?
2022-04-18 16:28:20.491 CST [1159] LOG: duration: 6215.926 ms statement: EXPLAIN (ANALYZE ON, BUFFERS ON) select 1 from information_schema.tables where table_schema = 'pg_catalog' and table_name = 'pg_file_settings'
Nested Loop (cost=0.68..17.88 rows=1 width=4) (actual time=0.126..0.128 rows=1 loops=1)
Join Filter: (c.relnamespace = nc.oid)
Buffers: shared hit=8 read=2
I/O Timings: read=0.027
-> Nested Loop Left Join (cost=0.68..16.81 rows=1 width=4) (actual time=0.085..0.087 rows=1 loops=1)
Buffers: shared hit=3 read=2
I/O Timings: read=0.027
-> Index Scan using pg_class_relname_nsp_index on pg_class c (cost=0.27..8.33 rows=1 width=8) (actual time=0.065..0.066 rows=1 loops=1)
Index Cond: (relname = 'pg_file_settings'::name)
Filter: ((relkind = ANY ('{r,v,f,p}'::"char"[])) AND (pg_has_role(relowner, 'USAGE'::text) OR has_table_privilege(oid, 'SELECT, INSERT, UPDATE, DELETE, TRUNCATE, REFERENCES, TRIGGER'::text) OR has_any_column_privilege(oid, 'SELECT, INSERT, UPDATE, REFERENCES'::text)))
Buffers: shared hit=1 read=2
I/O Timings: read=0.027
-> Nested Loop (cost=0.40..8.47 rows=1 width=4) (actual time=0.017..0.018 rows=0 loops=1)
Buffers: shared hit=2
-> Index Scan using pg_type_oid_index on pg_type t (cost=0.27..8.29 rows=1 width=8) (actual time=0.016..0.016 rows=0 loops=1)
Index Cond: (oid = c.reloftype)
Buffers: shared hit=2
-> Index Only Scan using pg_namespace_oid_index on pg_namespace nt (cost=0.13..0.17 rows=1 width=4) (never executed)
Index Cond: (oid = t.typnamespace)
Heap Fetches: 0
-> Seq Scan on pg_namespace nc (cost=0.00..1.06 rows=1 width=4) (actual time=0.038..0.038 rows=1 loops=1)
Filter: ((NOT pg_is_other_temp_schema(oid)) AND (nspname = 'pg_catalog'::name))
Rows Removed by Filter: 1
Buffers: shared hit=5
Planning:
Buffers: shared hit=168 read=52 written=5
I/O Timings: read=103.513 write=43.230
Planning Time: 184.492 ms
Execution Time: 0.438 ms
Edit:
After running analyze on the database, same results:
2022-04-18 17:53:04.563 CST [16398] LOG: duration: 5987.077 ms statement: EXPLAIN (ANALYZE ON, BUFFERS ON) select 1 from information_schema.tables where table_schema = 'pg_catalog' and table_name = 'pg_file_settings'
Nested Loop (cost=0.68..17.88 rows=1 width=4) (actual time=0.125..0.127 rows=1 loops=1)
Join Filter: (c.relnamespace = nc.oid)
Buffers: shared hit=8 read=2
I/O Timings: read=0.025
-> Nested Loop Left Join (cost=0.68..16.81 rows=1 width=4) (actual time=0.088..0.090 rows=1 loops=1)
Buffers: shared hit=3 read=2
I/O Timings: read=0.025
-> Index Scan using pg_class_relname_nsp_index on pg_class c (cost=0.27..8.33 rows=1 width=8) (actual time=0.069..0.070 rows=1 loops=1)
Index Cond: (relname = 'pg_file_settings'::name)
Filter: ((relkind = ANY ('{r,v,f,p}'::"char"[])) AND (pg_has_role(relowner, 'USAGE'::text) OR has_table_privilege(oid, 'SELECT, INSERT, UPDATE, DELETE, TRUNCATE, REFERENCES, TRIGGER'::text) OR has_any_column_privilege(oid, 'SELECT, INSERT, UPDATE, REFERENCES'::text)))
Buffers: shared hit=1 read=2
I/O Timings: read=0.025
-> Nested Loop (cost=0.40..8.47 rows=1 width=4) (actual time=0.016..0.016 rows=0 loops=1)
Buffers: shared hit=2
-> Index Scan using pg_type_oid_index on pg_type t (cost=0.27..8.29 rows=1 width=8) (actual time=0.014..0.014 rows=0 loops=1)
Index Cond: (oid = c.reloftype)
Buffers: shared hit=2
-> Index Only Scan using pg_namespace_oid_index on pg_namespace nt (cost=0.13..0.17 rows=1 width=4) (never executed)
Index Cond: (oid = t.typnamespace)
Heap Fetches: 0
-> Seq Scan on pg_namespace nc (cost=0.00..1.06 rows=1 width=4) (actual time=0.035..0.035 rows=1 loops=1)
Filter: ((NOT pg_is_other_temp_schema(oid)) AND (nspname = 'pg_catalog'::name))
Rows Removed by Filter: 1
Buffers: shared hit=5
Planning:
Buffers: shared hit=170 read=59 written=9
I/O Timings: read=105.688 write=79.773
Planning Time: 262.826 ms
Execution Time: 0.366 ms
Edit:
Analyze output after increasing shared_buffers to 25% of memory
Nested Loop (cost=0.68..17.88 rows=1 width=4) (actual time=0.096..0.098 rows=1 loops=1)
Join Filter: (c.relnamespace = nc.oid)
Buffers: shared hit=10
-> Nested Loop Left Join (cost=0.68..16.81 rows=1 width=4) (actual time=0.057..0.059 rows=1 loops=1)
Buffers: shared hit=5
-> Index Scan using pg_class_relname_nsp_index on pg_class c (cost=0.27..8.33 rows=1 width=8) (actual time=0.040..0.042 rows=1 loops=1)
Index Cond: (relname = 'pg_file_settings'::name)
Filter: ((relkind = ANY ('{r,v,f,p}'::"char"[])) AND (pg_has_role(relowner, 'USAGE'::text) OR has_table_privilege(oid, 'SELECT, INSERT, UPDATE, DELETE, TRUNCATE, REFERENCES, TRIGGER'::text) OR has_any_column_privilege(oid, 'SELECT, INSERT, UPDATE, REFERENCES'::text)))
Buffers: shared hit=3
-> Nested Loop (cost=0.40..8.47 rows=1 width=4) (actual time=0.014..0.014 rows=0 loops=1)
Buffers: shared hit=2
-> Index Scan using pg_type_oid_index on pg_type t (cost=0.27..8.29 rows=1 width=8) (actual time=0.012..0.012 rows=0 loops=1)
Index Cond: (oid = c.reloftype)
Buffers: shared hit=2
-> Index Only Scan using pg_namespace_oid_index on pg_namespace nt (cost=0.13..0.17 rows=1 width=4) (never executed)
Index Cond: (oid = t.typnamespace)
Heap Fetches: 0
-> Seq Scan on pg_namespace nc (cost=0.00..1.06 rows=1 width=4) (actual time=0.036..0.036 rows=1 loops=1)
Filter: ((NOT pg_is_other_temp_schema(oid)) AND (nspname = 'pg_catalog'::name))
Rows Removed by Filter: 1
Buffers: shared hit=5
Planning:
Buffers: shared hit=229
Planning Time: 7.866 ms
Execution Time: 0.306 ms