Re: BUG #16653: Regression in CTE evaluation

Bruce Momjian <bruce@momjian.us> writes:
> On Sun, Oct  4, 2020 at 04:18:43PM +0000, PG Bug reporting form wrote:
>> The following SQL worked in versions 9 through 12. It is throwing an error
>> in version 13.

> Uh, I am able to reproduce the error in PG _12_ as well, and I am sure
> it is related to this change in PG 12:

>       Allow common table expressions (CTEs) to be inlined into the outer query
>       (Andreas Karlsson, Andrew Gierth, David Fetter, Tom Lane)

Indeed.  The planner now inlines the WITH query, allowing
"CAST(exp_days.days || ' days' AS interval)" to be folded to a constant,
whereupon you get an error since indeed ' days' isn't valid interval
input.

Sorry, I reject the position that this is a bug.  It was something of
an implementation artifact that you didn't get this error before.
As of v12, we provide explicit control over whether a WITH query can
be inlined or not, and you need to use that control if you have a
query that's dependent on inlining not happening.

                        regards, tom lane