[GENERAL] views and fdw usage and performance
От | Armand Pirvu (home) |
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Тема | [GENERAL] views and fdw usage and performance |
Дата | |
Msg-id | C58163C7-F60A-4862-9E16-12166F838079@gmail.com обсуждение исходный текст |
Ответы |
Re: [GENERAL] views and fdw usage and performance
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Список | pgsql-general |
Hi I have two schemas jt1, and jt2 in the same db In both I have the same table tbl3 The idea is to keep in sync jt1.tbl3 from jt2.tbl3 each time I have an insert/update/delete on jt2.tbl3 So I was thinking about the following cases to avoid replication 1) in jt2 rather than have the tbl3 table, have a view named tbl3 based on jt1.tbl3 2) use the postgtres fdw and in jt2 have a foreign table tbl3 to jt1.tbl3 create table tbl3 (col1 integer, col2 integer, col3 integer, primary key (col1)); insert into tbl3 select generate_series(1, 10000000), 111,222; Questions: q1 - Any issues with this logic ? Or any other ways to do this better ? jt2 usage in terms of concurrent users and so onis by far much less than jt1, at least one order of magnitude less q2 - query performance (select * from tbl3 where col1=499123; ) . While using views it is clear cut the output of explain, on fdw not so much explain analyze select * from jt2.tbl3 where col1=874433; QUERY PLAN -------------------------------------------------------------------------------------------------------- Foreign Scan on tbl3 (cost=100.00..138.66 rows=11 width=12) (actual time=0.204..0.205 rows=1 loops=1) Planning time: 0.043 ms Execution time: 0.374 ms (3 rows) explain analyze select * from jt1.tbl3 where col1=874433; QUERY PLAN ----------------------------------------------------------------------------------------------------------------- Index Scan using tbl3_pkey on tbl3 (cost=0.43..8.45 rows=1 width=12) (actual time=0.010..0.011 rows=1 loops=1) Index Cond: (col1 = 874433) Planning time: 0.035 ms Execution time: 0.021 ms (4 rows) Do I understand correctly that the output of (explain analyze select * from jt2.tbl3 where col1=874433) is in essence (forall practical purposes) the same as the one from (explain analyze select * from jt1.tbl3 where col1=874433;) and nota sequential scan like the following ? explain analyze select * from jt1.tbl3 where col2=874433; QUERY PLAN -------------------------------------------------------------------------------------------------------- Seq Scan on tbl3 (cost=0.00..179053.25 rows=1 width=12) (actual time=498.020..498.020 rows=0 loops=1) Filter: (col2 = 874433) Rows Removed by Filter: 9999998 Planning time: 0.030 ms Execution time: 498.034 ms (5 rows) Thanks Armand
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