Re: Notes about Pl/PgSQL assignment performance

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(at)alvh(dot)no-ip(dot)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.