| From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
|---|---|
| To: | Bruce Momjian <pgman(at)candle(dot)pha(dot)pa(dot)us> |
| Cc: | "P(dot)J(dot) \"Josh\" Rovero" <rovero(at)sonalysts(dot)com>, pgsql-hackers(at)postgresql(dot)org |
| Subject: | Re: TOAST performance (was Re: [GENERAL] Delete Performance) |
| Date: | 2001-11-22 00:37:26 |
| Message-ID: | 26463.1006389446@sss.pgh.pa.us |
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| Lists: | pgsql-general pgsql-hackers |
Bruce Momjian <pgman(at)candle(dot)pha(dot)pa(dot)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 record that the old page is no longer active.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.
regards, tom lane
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