On Thu, Sep 7, 2023, at 4:46 PM, Michael Paquier wrote:
> On Thu, Sep 07, 2023 at 03:25:36PM +0700, Lepikhov Andrei wrote:
>> I invented a dummy extension "pg_extension" [1], commit 4199a0c,
>> which adds CustomScan over the first non-parameterized HashJoin at
>> the pathlist.
>> The example presented in my letter earlier causes the ERROR on
>> CTE. Moreover, if you remove the word 'materialized', you will find
>> the same error on Subquery.
>>
>> [1] https://github.com/danolivo/pg_extension/tree/main
>
> Digressing a bit here about this point.. In the long-term I think
> that it would be a good idea to have a template module in
> src/test/modules/ that shows how to use a CustomScan so as it is able
> to demonstrate how this stuff works, and to check if it is works as
> intended. With regression tests, of course.
I agree. I often use it in different situations: for scan, join purposes, as a stat gathering tool and others. Having
sometemplates in the code base would be comfortable. Also, We should remember to add some examples of extensible node
usage...
In the attachment - rewritten code of the CustomScan node, as mentioned earlier, as a test module with one regression
test.It shows both CTE and Subquery problems (they have different sources of error). Also, I have attached a patch that
fixesthe problem's symptoms - not the origins of the problem, just for demonstration.
--
Regards,
Andrei Lepikhov
