| From: | Bruce Momjian <bruce(at)momjian(dot)us> |
|---|---|
| To: | Robert Haas <robertmhaas(at)gmail(dot)com> |
| Cc: | Andres Freund <andres(at)2ndquadrant(dot)com>, Jeff Davis <pgsql(at)j-davis(dot)com>, Josh Berkus <josh(at)agliodbs(dot)com>, pgsql-hackers(at)postgresql(dot)org |
| Subject: | Re: removing PD_ALL_VISIBLE |
| Date: | 2013-05-31 17:14:13 |
| Message-ID: | 20130531171413.GA1728@momjian.us |
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| Thread: | |
| Lists: | pgsql-hackers |
On Thu, May 30, 2013 at 09:47:22AM -0400, Robert Haas wrote:
> Well, as Heikki points out, I think that's unacceptably dangerous.
> Loss or corruption of a single visibility map page means possible loss
> of half a gigabyte of data.
>
> Also, if we go that route, looking at the visibility map is no longer
> an optimization; it's essential for correctness. We can't decide to
> skip it when it seems expensive, for example, as Jeff was proposing.
Isn't the visibility map already required for proper return results as
we use it for index-only scans. I think the optimization-only ship has
sailed.
--
Bruce Momjian <bruce(at)momjian(dot)us> http://momjian.us
EnterpriseDB http://enterprisedb.com
+ It's impossible for everything to be true. +
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