On Thu, Aug 09, 2007 at 01:25:14PM +0100, Gregory Stark wrote: > "Pavan Deolasee" <[EMAIL PROTECTED]> writes: > > > HOT update is feasible iff > > > > - old and new tuples, both match the partiality condition OR > > - old and new tuples, both don't match the condition > ... > > For functional index, we should apply the function to the old and new > > tuple and compare the outcome. If the results are same, HOT update > > is feasible. > > This is debatable. We could compare the columns used in the partial condition > expression or function expression directly. If they're the same then the > expression or function must return the same value. If the function is quite > expensive then that might be cheaper. > > On the other hand if it's not expensive and the columns change frequently but > the results don't then we might be doing a lot of work for nothing.
If we're going to get this into 8.3 I think we should be leaning towards whatever is the simplest way to do it... -- Decibel!, aka Jim Nasby [EMAIL PROTECTED] EnterpriseDB http://enterprisedb.com 512.569.9461 (cell)
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