"Tom Lane" <[EMAIL PROTECTED]> 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

> 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

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