Re: reloption to prevent VACUUM from truncating empty pages at the end of relation

Andres Freund <andres(at)anarazel(dot)de> writes:
> On 2019-03-01 14:17:33 -0500, Tom Lane wrote:
>> I think we should reject the whole patch, tbh, and go do something
>> about the underlying problem instead. Once we've made truncation
>> not require AEL, this will be nothing but a legacy wart that we'll
>> have a hard time getting rid of.

> IDK, it's really painful in the field, and I'm not quite seeing us
> getting rid of the AEL for v12.

Dunno, I was musing about it just yesterday, in
https://postgr.es/m/1261.1551392263@sss.pgh.pa.us

I'd sure rather spend time making that happen than this. I'm also
not entirely convinced that we MUST do something about this in v12
rather than v13 --- we've been living with it ever since we had
in-core replication, why's it suddenly so critical?

> I think it's a wart, but one that works
> around a pretty important usability issue. And I think we should just
> remove the GUC without any sort of deprecation afterwards, if necessary
> we can add a note to the docs to that effect. It's not like preventing
> truncation from happening is a very intrusive / dangerous thing to do.

Well, if we add a reloption then we can never ever get rid of it; at
best we could ignore it. So from the perspective of how-fast-can-we-
deprecate-this, maybe a GUC is the better answer. On the other hand,
I'm not sure I believe that many installations could afford to disable
truncation for every single table.

regards, tom lane