Seamus Abshere <seamus@xxxxxxxxxxx> writes: > Who decides if a seemingly-useful aggregate is added to Postgres? There's no particularly well-defined process for it, but as far as these items ago: > 1. I just discovered first()/last() as defined in the wiki [1], where > it's noted that conversion from Access or Oracle is much easier with > them. Those are (a) undefined as to precise behavior, (b) redundant with the first_value/last_value window functions, which *are* well defined (not to mention SQL-standard), and (c) easy enough to make in SQL if you want them despite (a) and (b). So I don't really see them getting over the hump. > 2. We use our "homemade" jsonb_object_agg(jsonb) constantly, which is > modeled off of (built-in) json_object_agg(name, value) and (built-in) > jsonb_agg(expression). [2] I dunno, the semantics of using jsonb_concat as an aggregate transfn seem pretty squishy to me. It's certainly much less well-defined as to what you get than for either of the existing aggs you mention. The short answer really is that we spend a lot of sweat on making Postgres extensible so that we don't have to put in (and then maintain forever) every little special-purpose function somebody might want. regards, tom lane -- Sent via pgsql-general mailing list (pgsql-general@xxxxxxxxxxxxxx) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-general
