On 3/24/23 03:28, Dominique Devienne wrote:
> On Thu, Mar 23, 2023 at 4:20 PM Adrian Klaver <adrian.klaver@aklaver.com
> <mailto:adrian.klaver@aklaver.com>> wrote:
>
> On 3/23/23 04:12, Dominique Devienne wrote:
> > CROSS JOIN LATERAL UNNEST(cnstr.conkey) WITH ORDINALITY AS
> cols(value, rank)
> > ORDER BY cols.rank
> A before coffee solution:
>
>
> Thanks for answering Adrian. And sorry for the delay in responding.
>
> WITH ck AS (
> SELECT
> conrelid,
> unnest(conkey) AS ky
> FROM
> pg_constraint
> WHERE
> conrelid = 'cell_per'::regclass
> )
>
>
> This part surprised me. I didn't know a table-valued function could be
> used like this on the select-clause.
>
> Both queries below yield the same rows for me, in the same order:
>
> => select conname, unnest(conkey), conrelid::regclass::text from
> pg_constraint where conrelid::regclass::text like ... and
> cardinality(conkey) = 8;
> => select conname, key.value, conrelid::regclass::text from
> pg_constraint cross join lateral unnest(conkey) as key(value) where
> conrelid::regclass::text like ... and cardinality(conkey) = 8;
>
> So your compact form is equivalent to the second form?
> What about the order? Is it guaranteed?
> I was "raised" on the "order is unspecified w/o an order-by-clause". Why
> would be it be different here?
> In our case, the query is more complex, with joins on pg_namespace,
> pg_class, and pg_attribute, on
> all constraints of a schema, and the order came out wrong w/o adding
> WITH ORDINALITY and ordering on it.
Your original question was:
"But I'm wondering about getting 1 row per constraint instead,
and fetching an array of column names.
So is there a way to "convert" int2[] conkey array into a text[] of those
column names?"
That is what I showed as a simple example.
>
> Thus I worry the order is plan-dependent, and not guaranteed. Am I wrong
> to worry?
> The form you provide seems no different from our old form, to my
> non-expert eye. --DD
--
Adrian Klaver
adrian.klaver@aklaver.com
