Re: TOAST performance (was Re: [GENERAL] Delete Performance)

> Bruce Momjian <pgman@candle.pha.pa.us> writes:
> >> I don't see how that reduces the total amount of disk traffic?
> 
> > Well, right now we write the pre-image to WAL, then write the new page
> > over the old one.  In my case, you just write the new, and somewhere
> > record that the old page is no longer active.
> 
> The devil is in the details of that last little bit.  How is "mark a
> page inactive" cheaper than "mark a tuple dead"?  More specifically,
> how do you propose to avoid WAL-logging the page you are going to do
> this marking in?  Seems you still end up with a WAL page image for
> something.

I was thinking of just throwing the inactive page number into WAL.  Much
smaller than the entire page image.  You don't touch the page.  Does
that help?

--  Bruce Momjian                        |  http://candle.pha.pa.us pgman@candle.pha.pa.us               |  (610)
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