Re: making relfilenodes 56 bits

On Tue, 28 Jun 2022 at 13:45, Simon Riggs <simon.riggs@enterprisedb.com> wrote:
> but since the number of combinations is usually 1, but even then, low,
> it can be cached easily in a smgr array and included in the checkpoint
> record (or nearby) for ease of use.

I was reading the thread to keep up with storage-related prototypes
and patches, and this specifically doesn't sound quite right to me. I
do not know what values you considered to be 'low' or what 'can be
cached easily', so here's some field data:

I have seen PostgreSQL clusters that utilized the relative isolation
of seperate databases within the same cluster (instance / postmaster)
to provide higher guarantees of data access isolation while still
being able to share a resource pool, which resulted in several
clusters containing upwards of 100 databases.

I will be the first to admit that it is quite unlikely to be common
practise, but this workload increases the number of dbOid+spcOid
combinations to 100s (even while using only a single tablespace),
which in my opinion requires some more thought than just handwaving it
into an smgr array and/or checkpoint records.


Kind regards,

Matthias van de Meent