Re: Order of operations in lazy_vacuum_rel

Alvaro Herrera <alvherre(at)commandprompt(dot)com> writes:
> Tom Lane wrote:
>> Maybe we should do
>> something about this. There wasn't any obvious solution before,
>> but now that we have the nontransactional smgr-level sinval messages
>> being sent on drops and truncates, it seems like tying rd_targblock
>> clearing to those would fix the problem.

> Hmm, sounds good, though I confess not having heard about
> nontransactional sinval messages before.

Hey, they've been in there almost a week ;-)
http://archives.postgresql.org/pgsql-committers/2010-02/msg00026.php

>> The easiest way to do that
>> would involve moving rd_targblock down to the SMgrRelation struct.
>> Probably rd_fsm_nblocks and rd_vm_nblocks too. Comments?

> Can't say it doesn't look like a modularity violation from here --
> insertion target block doesn't really belong into smgr, does it?

It never belonged in relcache, either. Trying to keep dynamic state
(not backed by a catalog entry) in the relcache has always been a
pretty klugy thing. smgr at least has a reasonable excuse for trying
to keep track of physical truncation events, which is the thing we need
here.

regards, tom lane