Tom Lane <[EMAIL PROTECTED]> writes: > Lonni J Friedman <[EMAIL PROTECTED]> writes: > > > I'd like to be able to run vacuum in a 'test' or read-only mode where > > i'd see what it would do before actually running it. > > Er ... what possible value would that have? ISTM it would expend 80% of > the effort to achieve 0% of the result.
Just a guess, maybe you mean "analyze" when you say "vacuum"? People often conflate them since they often run both together with "vacuum analyze". But there wouldn't be much point in running a test vacuum, they're might be some point in running a test analyze. If so, one little known feature: you can run analyze inside a transaction. The new statistics are only used by that session until you commit. I started a script to explain a set of queries, run analyze, then re-explain the queries and compare the plans before either committing or rolling back. I think it would be a useful DBA tool for a high availability production system, but I haven't finished it. -- greg ---------------------------(end of broadcast)--------------------------- TIP 8: explain analyze is your friend
