Simon Riggs wrote: > Yes, the main point is that an UPDATE doesn't always allow you to prune.
You can always remove dead HOT tuples in heap_update. But you can never defragment the page at that point. > If it did, that would be the right place. Since it doesn't the best > place to prune is surely the first time we see we *can* prune. Not necessarily. Pruning is expensive, you need to scan all tuples on the page and write WAL record. And defragment the page if you consider that part of pruning. You don't want to do it too aggressively. -- Heikki Linnakangas EnterpriseDB http://www.enterprisedb.com ---------------------------(end of broadcast)--------------------------- TIP 3: Have you checked our extensive FAQ? http://www.postgresql.org/docs/faq
