Visibility map arrives

Since Heikki doesn't have a blog of his own, I will take it upon myself to blog about this one: he has just committed the initial version of the visibility map feature for PostgreSQL 8.4.

In short, this means that VACUUM will now only need to visit pages in a table that has actually changed. So if you have a large table where only a very few rows change, VACUUM will require significantly less CPU and I/O to run. With this lower cost, it's also possible to run VACUUM more often on large tables - if nothing at all has changed, it's more or less a no-op!

In the future, the hope is to be able to build on this patch to implement things like index-only scans - but that's for another version.

Yet another great feature for 8.4 - this is shaping up to be a very good release I think.


This is the kind of advancements that justify the upgrade worth any adaptation work!

Posted on Dec 3, 2008 at 15:11 by Vincenzo Romano.

This will be a great release, PostgreSQL will definitely have the most complete SQL dialect amongst opensource databases with CTE and Window Queries!

Posted on Dec 3, 2008 at 19:48 by pabloj.


I speak at and organize conferences around Open Source in general and PostgreSQL in particular.


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Stockholm, Sweden
PGConf.EU 2016
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Tallinn, Estonia
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Berlin, Germany
PGConf.Asia 2016
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FOSDEM + PGDay 2017
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Brussels, Belgium


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San Francisco, USA
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