Re: Remove xmin and cmin from frozen tuples - Mailing list pgsql-hackers

"Jim C. Nasby" <jnasby@pervasive.com> writes:
> If the 4 header fields in question were just normalized out, wouldn't
> all the semantics continue to work the same? All I'm envisioning is
> replacing them in each tuple with a pointer (vis_id) to another
> datastore that would be roughly equivalent to:

> CREATE TABLE visibility (
>     vis_id      SERIAL,
>     xmin        int,
>     xmax        int,
>     cmin        int,
>     cmax_xmax   int
> )

> Of course you wouldn't use an actual table to do this, but hopefully
> this clarifies my idea.

Let's see ... replace every tuple access with TWO tuple accesses
... yes, that should improve performance nicely.  And no, I'm not
sure the semantics are the same, particularly w.r.t. atomicity of
state changes.
        regards, tom lane