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(at)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