| From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
|---|---|
| To: | Robert Haas <robertmhaas(at)gmail(dot)com> |
| Cc: | Kevin Grittner <Kevin(dot)Grittner(at)wicourts(dot)gov>, pgsql-hackers(at)postgresql(dot)org |
| Subject: | Re: limiting hint bit I/O |
| Date: | 2011-01-14 19:09:36 |
| Message-ID: | 9459.1295032176@sss.pgh.pa.us |
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| Lists: | pgsql-hackers |
Robert Haas <robertmhaas(at)gmail(dot)com> writes:
> On Fri, Jan 14, 2011 at 1:42 PM, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
>> Um, yeah, I think you're having a problem keeping all the ideas straight
>> ;-). The argument about forensics has to do with how soon we're willing
>> to freeze tuples, ie replace the XID with a constant. Not about hint
>> bits.
> Those things are related, though. Freezing sooner could be viewed as
> an alternative to hint bits.
Freezing sooner isn't likely to reduce I/O compared to hint bits. What
that does is create I/O that you *have* to execute ... both in the pages
themselves, and in WAL.
regards, tom lane
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