Re: pglz performance

Hi,

On 2019-08-04 17:53:26 +0200, Petr Jelinek wrote:
> > 5) I wonder why compression_algorithm is defined as PGC_SIGHUP. Why not
> > to allow users to set it per session? I suppose we might have a separate
> > option for WAL compression_algorithm.
> > 
> 
> Yeah I was thinking we might want to change wal_compression to enum as well.
> Although that complicates the code quite a bit (the caller has to decide
> algorithm instead compression system doing it).

Isn't that basically required anyway? The WAL record will need to carry
information about the type of compression used, independent of
PGC_SIGHUP/PGC_USERSET, unless you want to make it an initdb option or
something super heavyweight like that.

We could just have the wal_compression assign hook set a the compression
callback and a compression type integer or such if we want to avoid
doing that kind of thing at runtime.

Greetings,

Andres Freund