On Wed, Sep 12, 2007 at 03:01:12PM -0500, Erik Jones wrote: > > On Sep 12, 2007, at 2:19 PM, Frank Schoep wrote: > > >On Sep 12, 2007, at 9:07 PM, Scott Marlowe wrote: > >>On 9/12/07, Mikko Partio <mpartio@xxxxxxxxx> wrote: > >>>? > >>>Aren't you mixing up REINDEX and CLUSTER? > >> > >>? > >>Either one does what a vacuum full did / does, but generally does > >>it better. > > > >On topic of REINDEX / VACUUM FULL versus a CLUSTER / VACUUM ANALYZE > >I'd like to ask if CLUSTER is safe to run on a table that is in > >active use. > > > >After updating my maintenance scripts from a VACUUM FULL (add me to > >the list) to CLUSTER (which improves performance a lot) I noticed I > >was getting "could not open relation ?" errors in the log while the > >scripts ran so I reverted the change. This was on 8.1.9. > > You'd probably see the same behavior on 8.2.x. CLUSTER is not > transactionally safe so you don't want to run CLUSTER on tables that > are actively being used. I believe that's been fixed for 8.3. Actually, that's a bit over-conservative... what happens prior to 8.3 is that CLUSTER rewrites the table using it's XID for everything. That can break semantics for any transactions that are running in serializable mode; if you're just using the default isolation level of read committed, you're fine with CLUSTER. -- Decibel!, aka Jim C. Nasby, Database Architect decibel@xxxxxxxxxxx Give your computer some brain candy! www.distributed.net Team #1828
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