Re: FOR PORTION OF should reject GENERATED columns

On 11.06.26 22:57, Paul A Jungwirth wrote:
> On Fri, May 15, 2026 at 2:04 PM Paul A Jungwirth
> <pj(at)illuminatedcomputing(dot)com> wrote:
>>> On Tue, May 12, 2026 at 1:34 PM Nathan Bossart
>>> <nathandbossart(at)gmail(dot)com> wrote:
>>>>
>>>> FOR PORTION OF doesn't seem to work well with virtual generated columns,
>>>> either. The following example seg-faults on my machine:
>>>>
>>>> create table t (a int, b int4range generated always as (int4range(a, a + 1)) virtual);
>>>> insert into t values (1);
>>>> delete from t for portion of b from 1 to 2;
>> My first fix was doing this check in the analysis phase because I
>> thought it would be hard to separate from moving other validations
>> into the planner/executor[1], but doing it as a stand-alone patch was
>> easier than I thought. Here is v2.
>>
>> [1] https://www.postgresql.org/message-id/626986.1776785090@sss.pgh.pa.us
>
> This needed a rebase; attached.
>
> Also I noticed it had some extra tests from the work to move FDW
> checks out of parse analysis. I've removed that from here and I'll
> make sure we have it in the right patch.

I don't understand why this proposed check is being done in the
executor. It seems to me that it should be done in the parser, in
transformForPortionOfClause(), where you check other properties of the
for-portion-of target column. It is not possible to turn a normal
column into a generated column, so once we have checked that the column
exists and has the right type and is not generated, I don't think there
is then any risk that that check becomes invalidated between parsing and
execution.