2013/1/23 Pavel Stehule <pavel.steh...@gmail.com>: > 2013/1/23 Tom Lane <t...@sss.pgh.pa.us>: >> Pavel Stehule <pavel.steh...@gmail.com> writes: >>> what should be result of concat(variadic NULL::int[]) >>> I enabled this use case, but what should be result? >> >> I think there are two somewhat defensible theories: >> >> (1) punt, and return NULL overall. So in this case the variadic >> function would act as if it were STRICT. That seems a bit weird though >> if the function is not strict otherwise. >> >> (2) Treat the NULL as if it were a zero-length array, giving rise to >> zero ordinary parameters. This could be problematic if the function >> can't cope very well with zero parameters ... but on the other hand, >> if it can't do so, then what will it do with VARIADIC '{}'::int[] ? > > This is repeated question - how much is NULL ~ '{}' > > There is only one precedent, I think > > postgres=# select '>>>' || array_to_string('{}'::int[], '') || '<<<'; > ?column? > ---------- > >>><<< > (1 row) > > postgres=# select '>>>' || array_to_string(NULL::int[], '') || '<<<'; > ?column? > ---------- > > (1 row) > > but this function is STRICT - so there is no precedent :(
next related example CREATE OR REPLACE FUNCTION public.myleast(VARIADIC integer[]) RETURNS integer LANGUAGE sql AS $function$ select min(v) from unnest($1) g(v) $function$ postgres=# select myleast(variadic array[]::int[]) is null; ?column? ---------- t (1 row) postgres=# select myleast(variadic null::int[]) is null; ?column? ---------- t (1 row) so it is close to Tom (2) concat(VARIADIC NULL::int[]) and concat(VARIADIC '{}'::int[]) should returns NULL it is little bit strange, but probably it is most valid Regards Pavel > >> >> I lean a little bit towards (2) but it's definitely a judgment call. >> Anybody have any other arguments one way or the other? >> > > > >> regards, tom lane -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers