Robert Haas wrote:
> To implement this in PostgreSQL, I believe we would need support for
> UNDO.
> - Reading a page that has been recently modified gets significantly
> more expensive; it is necessary to read the associated UNDO entries
> and do a bunch of calculation that is significantly more complex than
> what is required today.
As others have said, that is the main drawback.
Also, and related to this, ROLLBACK would become an expensive operation.
Yours,
Laurenz Albe
