Re: SLRUs in the main buffer pool - Page Header definitions

Hi,

On 2022-06-22 19:12:14 -0400, Tom Lane wrote:
> "Bagga, Rishu" <bagrishu@amazon.com> writes:
> > The current SLRU pages do not have any header, so there is a need to
> > create a new page header format for these. Our investigations revealed
> > that we need to:
> 
> > 1. track LSN to ensure durability and consistency of all pages (for redo
> >    and full page write purposes)
> > 2. have a checksum (for page correctness verification).
> > 3. A flag to identify if the page is a relational or BufferedObject
> > 4. Track version information.
> 
> Isn't this a nonstarter from the standpoint of pg_upgrade?

We're rewriting some relation forks as part of pg_upgrade (visibility map
IIRC?), so rewriting an SLRU is likely not prohibitive - there's much more of
a limit to the SLRU sizes than the number and aggregate size of relation
forks.

Greetings,

Andres Freund