On 02/22/2012 10:21 AM, Tom Lane wrote:
Robert Haas<robertmh...@gmail.com> writes:
Anyway, to your point, I suppose I might hesitate to mark factorial
leak-proof even if it didn't throw an error on overflow, because the
time it takes to return an answer for larger inputs does grow rather
rapidly. But it's kind of a moot point because the error makes it not
leak-proof anyway. So maybe we're just splitting hairs here, however
we decide to label this.
Speaking of hair-splitting ...
A strict interpretation of "no errors can be thrown" would, for example,
rule out any function that either takes or returns a varlena datatype,
since those are potentially going to throw out-of-memory errors if they
can't palloc a result value or a temporary detoasted input value.
I don't suppose that we want that, which means that this rule of thumb
is wrong in detail, and there had better be some more subtle definition
of what is okay or not, perhaps along the line of "must not throw any
errors that reveal anything useful about the input value". Have we got
such a definition? (I confess to not having followed this patch very
closely.)
Yeah.
Returning to the original point, I've come to the conclusion that "pure"
isn't the right way to go. The trouble with "leakproof" is that it
doesn't point to what it is that's not leaking, which is information
rather than memory, as many might imagine (and I did) without further
hints. I'm not sure any single English word would be as descriptive as
I'd like.
cheers
andrew
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