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 will be a great release, PostgreSQL will definitely have the most complete SQL dialect amongst opensource databases with CTE and Window Queries!
New comments can no longer be posted on this entry.
This is the kind of advancements that justify the upgrade worth any adaptation work!