Hi,
I did little change in Pavel code and this work properly, anybody can explain this?
do $$
declare
varv text = 'hello';
varc text = 'xxx';
begin
raise notice '%', case when 'int' = (select varc) then (select varv)::int else null end;
end;
$$;
--
Kind Regards
Sławomir Nowakiewicz
From: Pavel Stehule <pavel.stehule@gmail.com>
Sent: 23 July 2020 06:55
To: Tom Lane <tgl@sss.pgh.pa.us>
Cc: Slawomir Nowakiewicz <Slawomir.Nowakiewicz@rubix.com>; PostgreSQL mailing lists <pgsql-bugs@lists.postgresql.org>
Subject: Re: BUG #16549: "CASE" not work properly , the function works properly on PostgreSQL 9.6.8
Pavel Stehule <pavel.stehule@gmail.com> writes:
> What is interesting - it fails only when the subquery is in CASE condition
> expression. If is somewhere else, then it doesn't fail
If eval_const_expressions can simplify the CASE test condition itself
to constant-true or constant-false, then it throws away the unreachable
result expression(s) without const-simplifying them. So even if there
would have been a run-time error there, you don't see it.
Of course the error can only happen because we're trying to generate a
custom plan for the expression (with plpgsql variable values inserted
as constants not params). That's a bit silly in this example, but
it wouldn't happen if there weren't a sub-SELECT in the expression.
That forces use of the full planner and plancache machinery.
Thank you for explanation
regards, tom lane