"Tom Lane" <tgl@sss.pgh.pa.us> writes:
> 2. Page format conversion is WAL-logged as a complete page replacement
It seems we get that for free. By definition any modification to a page after
conversion will be the first record for that page since a checkpoint. It just
means we have to force full_page_writes to be true, at least for a buffer
that's been converted if not whenever we're processing a mixed format
database.
> On the whole I think we could define format conversions for user-defined
> types as "not our problem".
Hm, perhaps we could do it by doing as much of the work up-front as possible.
Requiring datatypes to define a function in pg_proc to do the conversion and
require that it be a function which can stand on its own without catalog
lookups or other facilities. Then when we start up on a mixed format database
we load all those functions into a hash by typeoid and provide that hash to
bufmgr. By definition any datatypes we expect to find in the database must
already be in the catalog before we start.
-- Gregory Stark EnterpriseDB http://www.enterprisedb.com
