Jeff Davis <pgsql@j-davis.com> writes:
> I'm sure this has been brought up before, does someone have a pointer to
> a discussion about doing VACUUM-like work in a sequential scan?

Yeah, it's been discussed before; try looking for "incremental vacuum"
and such phrases.

The main stumbling block is cleaning out index entries for the
known-dead heap tuple. The current VACUUM design amortizes that cost
across as many dead heap tuples as it can manage; doing it retail seems
inevitably to be a lot more expensive.

regards, tom lane

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Tom Lane wrote:
> Jeff Davis <pgsql@j-davis.com> writes:
> > I'm sure this has been brought up before, does someone have a pointer to
> > a discussion about doing VACUUM-like work in a sequential scan?
>
> Yeah, it's been discussed before; try looking for "incremental vacuum"
> and such phrases.
>
> The main stumbling block is cleaning out index entries for the
> known-dead heap tuple. The current VACUUM design amortizes that cost
> across as many dead heap tuples as it can manage; doing it retail seems
> inevitably to be a lot more expensive.

Maybe what we could do is have a seqscan save known-dead tuple IDs in a
file, and then in a different operation (initiated by autovacuum) we
would remove those TIDs from indexes, before the regular heap scan.

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

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