On Wed, Jan 5, 2011 at 3:22 PM, Jesper Krogh <jesper(at)krogh(dot)cc> wrote:
> Given a crash-safe visibility map, what purpuse does the PD_ALL_VISIBLE bit
> serve?

If we modify a page on which PD_ALL_VISIBLE isn't set, we don't
attempt to update the visibility map.  In theory, this is an important
optimization to reduce contention on the visibility map page, since
there are something like 64K heap pages per visibility map page.  In
practice, I'm not sure in what workloads it matters or by how much.

-- 
Robert Haas
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company

In response to

• Re: crash-safe visibility map, take three at 2011-01-05 20:22:54 from Jesper Krogh

Responses

• Re: crash-safe visibility map, take three at 2011-01-06 07:00:29 from Jesper Krogh
• Re: crash-safe visibility map, take three at 2011-01-07 18:28:54 from Jim Nasby

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