Jan Wieck wrote:
> Does ['15:15:00','15:15:00') make any more sense? Doesn't this
> essentially mean
>
> >= '15:15:00' && < '15:15:00'
>
> which again doesn't include a single point on the time line?
It defines a position in time with zero duration.
Some of the graphics programming I
On 2/11/2011 1:50 PM, Kevin Grittner wrote:
Josh Berkus wrote:
if I, in one of my applications, accidentally defined something
as having the range '('15:15:00','15:15:00')', I would *want* the
database to through an error and not accept it.
I can agree with that, but I think that range '[
On Fri, Feb 11, 2011 at 10:11:45AM -0800, Jeff Davis wrote:
> The cost, of course, is that not all operations are well-defined for
> empty ranges. I think those are mostly operators like those mentioned in
> the other thread: ">>" (strictly right of), "<<" (strictly left of), and
> "-|-" (adjacent)
FWIW, a very informal survey of probabilists didn't yield any reason
for trying to put an order on the empty set ( unless the metric was
cardinality or other equivalence relation ).
I think the problem here is that the idea of union and intersection
forming a ring over sets is being conflated with
Jeff Davis wrote:
>> Perhaps it was a mistake to get so concrete rather than
>> conceptual -- basically, it seems like it could be a useful
>> concept for any planned or scheduled range with an indeterminate
>> end point, which you want to "reserve" up front and record in
>> progress until compl
On Fri, 2011-02-11 at 15:14 -0500, Robert Haas wrote:
> On Fri, Feb 11, 2011 at 3:03 PM, Jeff Davis wrote:
> > Well, there is a certain amount of localized clarity, I will agree with
> > that. The complexity comes when you accidentally rely on some
> > transformation which seems logically sound, b
On Fri, 2011-02-11 at 14:19 -0600, Kevin Grittner wrote:
> Well, in the receipt number example there are multiple ranges in use
> for each year, and ranges for multiple years. If we get to the idea
> of a multi-ranges, this would be very handy for certain types of
> reports -- especially for audit
Jeff Davis wrote:
> Trying to incorporate a "start value" is adding extra information
> in there, and it's not really a part of the same algebra. It
> sounds more like a contiguous sequence with a "start value" and a
> "current value" to me.
Well, in the receipt number example there are multip
On Fri, Feb 11, 2011 at 3:03 PM, Jeff Davis wrote:
> Well, there is a certain amount of localized clarity, I will agree with
> that. The complexity comes when you accidentally rely on some
> transformation which seems logically sound, but could result in a
> transient empty range, which then throw
On Fri, 2011-02-11 at 14:14 -0500, Robert Haas wrote:
> > It's really that it has nice mathematical properties coming from set
> > theory. Take the distributive law:
> >
> > A UNION (B INTERSECT C) = (A UNION B) INTERSECT (A UNION C)
>
> But the basic range type isn't even closed under UNION.
An
On Fri, 2011-02-11 at 13:50 -0500, Robert Haas wrote:
> On Fri, Feb 11, 2011 at 1:11 PM, Jeff Davis wrote:
> > Similarly, "intersection" of ranges is somewhat analogous to
> > multiplication of numbers.
>
> I had a feeling that we might be going in this direction. It strikes
> me that this case
On Feb 11, 2011, at 10:28 AM, Josh Berkus wrote:
> So, if we allow empty ranges of this kind, I would want a GUC for
> "allow_empty_ranges".
GUC you, josh. ;-P
D
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On Fri, 2011-02-11 at 13:08 -0600, Kevin Grittner wrote:
> It makes more sense in the context of a range of some type with a
> clearly defined granularity. Our accounting system, for example,
> can assign a new range of receipt IDs for each calendar year. If
> you want a variable to represent the
"Kevin Grittner" wrote:
> Basically, with a type having well-defined granularity, a [) range
> could usefully represent, "start to last used", and start out
> empty.
I guess that would actually be "start to next available"
-Kevin
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On Fri, Feb 11, 2011 at 2:06 PM, Jeff Davis wrote:
> On Fri, 2011-02-11 at 10:28 -0800, Josh Berkus wrote:
>> I guess I'm having trouble tying the concept of empty ranges to any
>> reality external to the database.
>
> That's true, but in the same sense as zero has no meaning outside of the
> data
Robert Haas wrote:
>> I think that range '[15:15:00,15:15:00)' should be valid as a
>> zero-length range between, for example, '[15:00:00,15:15:00)' and
>> '[15:15:00,15:30:00)'.
>
> How would that actually work? I kind of agree with Josh: I'd be
> inclined to make the type input function boot
On Fri, 2011-02-11 at 10:28 -0800, Josh Berkus wrote:
> I guess I'm having trouble tying the concept of empty ranges to any
> reality external to the database.
That's true, but in the same sense as zero has no meaning outside of the
database.
It's really that it has nice mathematical properties c
On Fri, Feb 11, 2011 at 1:50 PM, Kevin Grittner
wrote:
> Josh Berkus wrote:
>
>> if I, in one of my applications, accidentally defined something
>> as having the range '('15:15:00','15:15:00')', I would *want* the
>> database to through an error and not accept it.
>
> I can agree with that, but I
On Fri, Feb 11, 2011 at 1:11 PM, Jeff Davis wrote:
> Similarly, "intersection" of ranges is somewhat analogous to
> multiplication of numbers.
I had a feeling that we might be going in this direction. It strikes
me that this case is a bit like division by zero. It's kind of a
nuisance that divi
Josh Berkus wrote:
> if I, in one of my applications, accidentally defined something
> as having the range '('15:15:00','15:15:00')', I would *want* the
> database to through an error and not accept it.
I can agree with that, but I think that range '[15:15:00,15:15:00)'
should be valid as a ze
Jeff Davis wrote:
> The philosophy is that they are essentially the "zero" value of
> any range type. Like the number zero, it allows closure over
> operations that would otherwise return an error.
Well, zero has a pretty well defined and easy to understand meaning.
How many ostriches do you h
On 2/11/11 10:11 AM, Jeff Davis wrote:
> Thoughts? Do the benefits outweigh the costs?
I guess I'm having trouble tying the concept of empty ranges to any
reality external to the database.
For example, what would the time range:
'('15:15:00','15:15:00')'
... represent exactly? "A non-existant
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