Re: xid wraparound danger due to INDEX_CLEANUP false

On 2020-May-06, Peter Geoghegan wrote:

> Also, do we really want to skip summarization of BRIN indexes? This
> cleanup is rather dissimilar to the cleanup that takes place in most
> other AMs -- it isn't really that related to garbage collection (BRIN
> is rather unique in this respect). I think that BRIN might be an
> inappropriate target for "index_cleanup off" VACUUMs for that reason.
> 
> See the explanation of how this takes place from the docs:
> https://www.postgresql.org/docs/devel/brin-intro.html#BRIN-OPERATION

Good question.  I agree that BRIN summarization is not at all related to
what other index AMs do during the cleanup phase.  However, if the
index_cleanup feature is there to make it faster to process a table
that's nearing wraparound hazards (or at least the warnings), then I
think it makes sense to complete the vacuum as fast as possible -- which
includes not trying to summarize it for brin indexes.

-- 
Álvaro Herrera                https://www.2ndQuadrant.com/
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