| From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
|---|---|
| To: | Robert Haas <robertmhaas(at)gmail(dot)com> |
| Cc: | Jeff Davis <pgsql(at)j-davis(dot)com>, Bruce Momjian <bruce(at)momjian(dot)us>, Heikki Linnakangas <heikki(dot)linnakangas(at)enterprisedb(dot)com>, pgsql-hackers(at)postgresql(dot)org |
| Subject: | Re: crash-safe visibility map, take three |
| Date: | 2010-12-01 21:27:28 |
| Message-ID: | 21728.1291238848@sss.pgh.pa.us |
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| Lists: | pgsql-hackers |
Robert Haas <robertmhaas(at)gmail(dot)com> writes:
> If we switched from per-tuple MVCC based on XIDs to per-page MVCC
> based on LSNs and a rollback segment, all of this stuff would go out
> the window. Hint bits, gone. Anti-wraparound VACUUM, gone. CRCs,
> feasible. Visibility map... we might still need that, but the
> page-level bits go away.
> Of course, it would also create new problems.
Yup, we've seen that proposal before. It's called Oracle. There's
no good reason to believe that we'd have a net win after we were done
switching over ... not to mention the likelihood that they hold a ton
of patents about particular aspects of doing things that way.
regards, tom lane
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