Re: Automatic free space map filling

Zeugswetter Andreas DCP SD wrote:
>
> > > But you could do the indexes first and remember how far you
> > can vacuum
> > > the heap later.
> >
> > But the indexes _can't_ be done first; you _first_ need to
> > know which tuples are dead, which requires looking at the
> > table itself.
>
> If we already had the "all tuples visible" bitmap I think we could
> first scan the bitmap and decide whether we can afford to look
> at the visibility info for each entry in the index.
>
> We only collect the ctids before so we don't have the inefficient
> lookups,
> but if we can avoid the lookup in most cases it would again be
> attractive.

The problem is that index to heap lookups are very slow.

--
Bruce Momjian http://candle.pha.pa.us
SRA OSS, Inc. http://www.sraoss.com

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