Re: New VACUUM FULL

Itagaki Takahiro wrote:

> We still need traditional VACUUM FULL behavior for system catalog because
> we cannot change relfilenode for them. Also, VACUUM FULL REPLACE is not
> always better than traditional VACUUM FULL; the new version requires
> additional disk space and might be slower if we have a few dead tuples.

Tom was saying that we could fix the problem that relfilenode could not
be changed by having a flat file filenode map.  It would only be needed
for nailed system catalogs (the rest of the tables grab their
relfilenode from pg_class as usual) so it wouldn't have the problems
that the previous flatfiles had (which was that they could grow too
much).  I don't recall if this got implemented (I don't think it did).

As for it being slower with few dead tuples, I don't think this is a
problem -- just use lazy vacuum in that case.

I also remember we agreed on something about the need for extra disk
space, but I can't remember what it was.

-- 
Alvaro Herrera                                http://www.CommandPrompt.com/
The PostgreSQL Company - Command Prompt, Inc.