Re: BUG #16549: "CASE" not work properly , the function works properly on PostgreSQL 9.6.8

čt 23. 7. 2020 v 0:17 odesílatel Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> napsal:

> Pavel Stehule <pavel(dot)stehule(at)gmail(dot)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

Pavel

>
> regards, tom lane
>