Re: Move pg_attribute.attcompression to earlier in struct for reduced size?

On Thu, May 27, 2021 at 03:52:06PM -0700, Peter Geoghegan wrote:
> On Thu, May 27, 2021 at 1:29 PM Tom Lane <tgl@sss.pgh.pa.us> wrote:
>> Yeah.  My belief here is that users might bother to change
>> default_toast_compression, or that we might do it for them in a few
>> years, but the gains from doing so are going to be only incremental.
>> That being the case, most DBAs will be content to allow the older
>> compression method to age out of their databases through routine row
>> updates.  The idea that somebody is going to be excited enough about
>> this to run a downtime-inducing VACUUM FULL doesn't really pass the
>> smell test.
> 
> That was my original understanding of your position, FWIW. I agree
> with all of this.

If one wishes to enforce a compression method on a table, the only way
I could see through here, able to bypass the downtime constraint, is 
by using logical replication.  Anybody willing to enforce a new
default compression may accept the cost of setting up instances for
that.
--
Michael