Every PostgreSQL release adds new features, but sometimes the key to a release has less to do with what you add than with what you take away. PostgreSQL 8.4, for example, removed the settings max_fsm_pages and max_fsm_relations, and replaced them with a per-relation free space map that no longer requires manual sizing. Those parameters are now gone, and more importantly, something that you previously needed to understand and manage was replaced with something that just works. People who are still running PostgreSQL 8.3, or older versions, want to understand exactly how the free space map works; people who are running PostgreSQL 8.4, or newer, don't care. It's enough to know that it does work.
Now, about eight months ago, I wrote a blog entry on troubleshooting stuck vacuums. I would not say that this is an everyday problem, but in ten years of working with PostgreSQL, I've seen it a few times, and it's very unpleasant. It's easy to miss the fact that you have a problem at all, because in most cases, nothing immediately breaks. Instead, system performance just slowly degrades, gradually enough that you may not realize what the problem is until things have gotten pretty bad and you need to CLUSTER or VACUUM FULL to recover.
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Now, about eight months ago, I wrote a blog entry on troubleshooting stuck vacuums. I would not say that this is an everyday problem, but in ten years of working with PostgreSQL, I've seen it a few times, and it's very unpleasant. It's easy to miss the fact that you have a problem at all, because in most cases, nothing immediately breaks. Instead, system performance just slowly degrades, gradually enough that you may not realize what the problem is until things have gotten pretty bad and you need to CLUSTER or VACUUM FULL to recover.
Read more »
