Re: BUG #19487: Error while executing SQL query involving XML parsing

сб, 29 авг. 2026 г. в 00:55, Andrey Rachitskiy <pl0h0yp1(at)gmail(dot)com>:

>
>
> сб, 29 авг. 2026 г. в 00:49, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>:
>
>> Andrey Rachitskiy <pl0h0yp1(at)gmail(dot)com> writes:
>> > # Proposal Fix
>> > Fold constant `XmlExpr` in `eval_const_expressions` (same path as
>> > `MinMaxExpr` / `ArrayExpr`), so `IS DOCUMENT` becomes a boolean Const
>> and
>> > CASE drops the unused arm before simplifying `xpath()`.
>>
>> I don't object to simplifying XmlExpr where possible, but this patch
>> appears to believe that every variant of XmlExpr is immutable.
>> This is demonstrably false, eg
>>
>> regression=# set timezone = 'America/New_York';
>> SET
>> regression=# SELECT xmlforest('2026-08-28 12:00 UTC'::timestamptz AS foo);
>> xmlforest
>> --------------------------------------
>> <foo>2026-08-28T08:00:00-04:00</foo>
>> (1 row)
>>
>> regression=# set timezone = 'America/Chicago';
>> SET
>> regression=# SELECT xmlforest('2026-08-28 12:00 UTC'::timestamptz AS foo);
>> xmlforest
>> --------------------------------------
>> <foo>2026-08-28T07:00:00-05:00</foo>
>> (1 row)
>>
>> So you need to take a closer look at which variants can be promised to
>> be immutable.
>>
>>
Dear Tom, have a nice weekend!

In v2, I tried to take all the points into account and expanded the tests.

--
Regards,
Rachitskiy Andrey