Re: plans for PostgreSQL 12

Hi,

On 2018-06-05 06:32:31 +0200, Pavel Stehule wrote:
> ./configure --with-libxml --enable-tap-tests --enable-debug --with-perl
> CFLAGS="-ggdb -Og -g3 -fno-omit-frame-pointer"
>
> [pavel@nemesis postgresql]$ gcc --version
> gcc (GCC) 8.1.1 20180502 (Red Hat 8.1.1-1)
>
> I executed simple script
>
>  do $$ declare i bigint = 1; s bigint = 0; begin while i <= 100000000 loop
> s := s + i; i := i + 1; end loop;  raise notice '%', s; end $$;
>
>    7,68%  postmaster  postgres           [.]
> GetSnapshotData                               ▒
>    7,53%  postmaster  plpgsql.so         [.]
> exec_eval_simple_expr                         ▒
>    6,49%  postmaster  postgres           [.]

It seems to me the right fix here isn't a new class of functions, but
rather support for delaying the computation of the snapshot to the point
it's needed.  That'll be far more generically applicable and doesn't
require user interaction.

> ExecInterpExpr                                ▒
>    4,13%  postmaster  postgres           [.]

So we're going to need to optimize this further as well, I've a pending
patch for that, luckily ;)

> LWLockRelease                                 ▒
>    4,12%  postmaster  postgres           [.]

That's also GetSnapshotData()...

Greetings,

Andres Freund