Heikki Linnakangas wrote: > Stefan Kaltenbrunner wrote: >> Heikki Linnakangas wrote: >>> There's three things clearly missing in the patch: >>> >>> 1. HOT updates on tables with expression or partial indexes. Hasn't been >>> done yet because it should be pretty straightforward and we've had more >>> important things to do. Though not critical, should be finished before >>> release in my opinion. >> sounds like a rather common use case to me and I think this should >> really be in a patch that is accepted for 8.3... >> >>> 2. Pointer swinging. At the moment, after a row is HOT updated, the only >>> way to get rid of the redirecting line pointer is to run VACUUM FULL or >>> CLUSTER (or delete or cold update the row and vacuum). If we want to >>> implement pointer swinging before release, we have to get started now. >>> If we're happy to release without it and address the issue in later >>> releases if it seems important, we need to make a conscious decision on >>> that, now. I personally think we can release without it. >> hmm - I don't really understand most of the stuff behind HOT but does >> this mean that VACUUM FULL (or CLUSTER) is becoming a recommended or >> even required routine maintenance task for people using HOT ? > > No. A redirecting line pointer only takes 4 bytes, which isn't that much > in the scheme of things. If you don't mind wasting those 4 bytes per HOT > updated row, you don't need to run VACUUM FULL.
ah I see - that sounds like much less a problem than I thought it was. Thanks for the explaination! > > Note that 8.3 will decrease the tuple header size by 4 bytes thanks to > the combocid patch, and the varvarlen patch saves some more space on > tuples with short varlen fields. Even if you have an extra line pointer > for every row, 8.3 will still be at least as good as 8.2 with regard to > storage size. yep - I'm already playing with -HEAD for some of our production databases and the size improvements in itself are a very nice thing. Stefan ---------------------------(end of broadcast)--------------------------- TIP 2: Don't 'kill -9' the postmaster
