Re: New strategies for freezing, advancing relfrozenxid early

On Wed, Sep 14, 2022 at 11:33 PM Peter Geoghegan <pg(at)bowt(dot)ie> wrote:
>
> On Wed, Sep 14, 2022 at 3:18 AM John Naylor

> > Furthermore, it doesn't have to anticipate the maximum size, so there
> > is no up front calculation assuming max-tuples-per-page, so it
> > automatically uses less memory for less demanding tables.
>
> The final number of TIDs doesn't seem like the most interesting
> information that VM snapshots could provide us when it comes to
> building the dead_items TID data structure -- the *distribution* of
> TIDs across heap pages seems much more interesting. The "shape" can be
> known ahead of time, at least to some degree. It can help with
> compression, which will reduce cache misses.

My point here was simply that spilling to disk is an admission of
failure to utilize memory efficiently and thus shouldn't be a selling
point of VM snapshots. Other selling points could still be valid.

--
John Naylor
EDB: http://www.enterprisedb.com