[postgis-devel] EMPTY

[Paragon Corporation]

They should all be false.

Isn't the first requirement of containment/contains be that the two
geometries intersect -- so if we say empty can't intersect with anything
including empty, how can anything possibly contain  it?

Though have to pull out my sql server 2008 to see if it is in agreement.

Thanks,
Regina

 

-----Original Message-----
From: postgis-devel-bounces at postgis.refractions.net
[mailto:postgis-devel-bounces at postgis.refractions.net] On Behalf Of Paul
Ramsey
Sent: Tuesday, October 06, 2009 4:39 PM
To: PostGIS Development Discussion
Subject: Re: [postgis-devel] EMPTY

In the spirit of maintaining the geometry logical flow, what do you think of
these ideas?

 * ST_Contains(geometry, empty) == TRUE
 * ST_Within(geometry, empty) == FALSE
 * ST_Contains(empty, geometry) == FALSE
 * ST_Within(empty, geometry) == TRUE

What does SQL Server say?

P

On Tue, Oct 6, 2009 at 1:34 PM, Paul Ramsey <pramsey at cleverelephant.ca>
wrote:
> I'm going to change my intersection/disjoint answers to agree w/ SQL 
> Server. They are not bad, and they maintain the symmetry between where 
> intersection => ! disjoint.
>
> P.
>
> On Tue, Oct 6, 2009 at 12:45 PM, Chris Hodgson <chodgson at refractions.net>
wrote:
>> I moved these and summarized the interesting results from SQL Server 
>> 2008 next to your original lines Paul.
>>
>> Note that SQL Server says that everything is disjoint from empty, 
>> including empty itself - whereas your original guesses were to return
false.
>>
>> So far I think I like SQL Server's answers. Would be good to compare 
>> with oracle spatial too.
>>
>> Chris
>>
>> Paul Ramsey wrote:
>>>
>>> Regina, could you move your SQL Server examples down to a big block 
>>> at the end, so the main part of the document is more readable? So 
>>> far I agree with SQL Server in all the examples! Those guys are 
>>> smart! :)
>>>
>>> P
>>>
>>> On Tue, Oct 6, 2009 at 12:12 PM, Paul Ramsey 
>>> <pramsey at cleverelephant.ca>
>>> wrote:
>>>
>>>>
>>>> On Tue, Oct 6, 2009 at 12:03 PM, Chris Hodgson 
>>>> <chodgson at refractions.net>
>>>> wrote:
>>>>
>>>>
>>>>>
>>>>> I would dare say that geometry empty is more like zero, than null.
>>>>>
>>>>
>>>> Bingo, there's a useful mental model. Wikify that!
>>>>
>>>>
>>>
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>>
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>
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