Tomas Vondra wrote: > > We need an API for physical column reordering, even if it's just pg_ > > functions. The reason is that we want to enable people writing their > > own physical column re-ordering tools, so that our users can figure out > > for us what the best reordering algorithm is. > > I doubt that. For example, do you realize you can only do that while the > table is completely empty, and in that case you can just do a CREATE > TABLE with the proper order?
Not if you have views or constraints depending on the table definition -- it's not trivial to drop/recreate the table in that case, but you can of course think about truncating it, then reorder columns, then repopulate. Even better you can cause a full table rewrite if needed. > But if we want to allow users to define this, I'd say let's make that > part of CREATE TABLE, i.e. the order of columns defines logical order, > and you use something like 'AFTER' to specify physical order. > > CREATE TABLE test ( > a INT AFTER b, -- attlognum = 1, attphysnum = 2 > b INT -- attlognum = 2, attphysnum = 1 > ); Surely you want an ALTER command as a minimum; perhaps that is enough and there is no need for options in CREATE. > It might get tricky because of cycles, though. If there's a cycle, just raise an error. -- Álvaro Herrera http://www.2ndQuadrant.com/ PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
