Re: iscacheable for date/time?

Thomas Lockhart wrote:

> ... and how about the istrusted attribute for various routines? Should
> it be always false or always true for C builtin functions? How about for
> builtin SQL functions which are built on top of trusted C functions? Are
> we guarding against catalog changes on the underlying C routines?

I have always had trouble with the "iscacheable" flag, there needs to be a
number of "cache" levels:

(1) cache per transaction, so you can use a function in a where statement
and it does not force a table scan. IMHO this should be the default for all
functions, but is not supported in PostgreSQL.

(2) nocache, which would mean it forces a tables scan. This is the current
default.

(3) global cache, which means the results can be stored in perpetuity, this
is the current intended meaning of iscacheable.