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.
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