"Albert REINER" <areiner(at)tph(dot)tuwien(dot)ac(dot)at> writes:
> Suppose some _cachable_ function f is expensive, but its results are
> often needed. So, to speed up queries, we have an index on
> f(table.field). I wonder what happens when we update a tuple of that
> table: will f be re-computed if table.field is not changed?
Yes.
regards, tom lane