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Re: crash-safe visibility map, take three

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: (view raw, whole thread or download thread mbox)
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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