Re: Heavy write activity on first vacuum of fresh TOASTa

[Matthew <matthew(at)flymine(dot)org>]

On Thu, 13 Dec 2007, Simon Riggs wrote:
> On Thu, 2007-12-13 at 09:46 -0600, Kevin Grittner wrote:
> > Even though there have been no rollbacks, updates, or deletes on this
> > table, the vacuum is writing as much as it is reading while dealing
> > with the TOAST data.
>
> Writing hint bits. Annoying isn't it? :-(

Interesting thread. Now, I know absolutely nothing about how the data is
stored, but it strikes me as being non-optimal that every single block on
the disc needs to be written again just to update some hint bits. Could
those bits be taken out into a separate bitmap stored somewhere else? That
would mean the (relatively small) amount of data being written could be
written in a small sequential write to the disc, rather than very sparsely
over the whole table.

Matthew

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