Hi 2017-12-19 12:28 GMT+01:00 Андрей Жиденков <pensna...@gmail.com>:
> Few day ago a faced a problem: Pl/PgSQL procedure works slower when > running in parallel threads. I found the correlation between number of > assignments in procedure code and performance. I decided to write the > simple benchmark procedures and perform some test on PostgreSQL 9.6.5 > database installed on the server with 20 CPU cores (2 Xeon E5-2690V2 CPUs). > > This benchmark showed me that a simple Pl/PgSQL procedure with a simple > loop inside works slower when running even in 2 threads. There is a > procedure: > > CREATE OR REPLACE FUNCTION benchmark_test() RETURNS VOID AS $$ > DECLARE > v INTEGER; i INTEGER; > BEGIN > for i in 1..1000 loop > v := 1; > end loop; > END; > $$ LANGUAGE plpgsql; > > What is the point? I know, that Pl/PgSQL performs a SELECT query to > calculate each value for assignment but I didn't expect that it produce > side effects like this. If there is some buffer lock or anything else? > I am little bit lost when you are speaking about threads. Postgres doesn't use it. your test is not correct - benchmark_test should be marked as immutable. What will be result? Regards Pavel > > I've been written a post with charts and detailed explanation to display > these side effects: http://telegra.ph/Notes-about-PlPgSQL- > assignment-performance-12-19 > > Any help would be greatly appreciated. > -- > >
