Re: Notes about Pl/PgSQL assignment performance
| От | Andrey Zhidenkov |
|---|---|
| Тема | Re: Notes about Pl/PgSQL assignment performance |
| Дата | |
| Msg-id | CAN=gQ4B+Lkx2hVs9qY9q7jkjJv8gMJ04GO7FYTOHraxTy-5r9w@mail.gmail.com обсуждение исходный текст |
| Ответ на | Re: Notes about Pl/PgSQL assignment performance (Alvaro Herrera <alvherre@alvh.no-ip.org>) |
| Ответы |
Re: Notes about Pl/PgSQL assignment performance
Re: Notes about Pl/PgSQL assignment performance |
| Список | pgsql-hackers |
I've digged into the source code a little bit and found that chain:
PLPGSQL_STMT_ASSIGN -> exec_stmt_assign() -> exec_assign_expr() -> exec_eval_expr() -> exec_run_select() -> SPI_execute_plan_with_paramlist() -> _SPI_execute_plan() which finnaly calls PushActiveSnapshot() and PopActiveSnapshot() wich just do memory context allocations and use malloc() to copy snaphot.
Maybe I have missed something?
On Tue, Dec 19, 2017 at 4:34 PM, Alvaro Herrera <alvherre@alvh.no-ip.org> wrote:
Andrey Zhidenkov wrote:
> When I run this test in 2 threads I expect that running time will be the
> same, because PostgreSQL will fork process for the second connection and
> this process will be served by a separate CPU core because I have more than
> 2 cores.
> Yes, IMMUTABLE flag helps, but I think It's just because Postgres actually
> executes procedure only once.
Just a guess without actually looking at the WaitEvents (which you
should do) is that this is blocking on snapshot acquisition or something
like that.
--
Álvaro Herrera https://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services
С уважением, Андрей Жиденков.
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