[postgis-users] C++ and Postgis

[Pedro Doria Meunier]

Paul,

I could just *kiss* you mate! :D
(Right now I'm feeling pretty ashamed for not thinking of it right away 
... :] guess it's been too many hours coding... )

All the best,
Pedro.


On 11/23/2009 10:45 PM, Paul Ramsey wrote:
> If it's just points, do it all on the server side, skip encoding formats
>
> select st_x(pt) as x, st_y(pt) as y from mytable where myclause();
>
> P.
>
> On Mon, Nov 23, 2009 at 2:43 PM, Pedro Doria Meunier
> <pdoria at netmadeira.com>  wrote:
>    
>> Thank you Paul and John for your ideas. :)
>>
>> Actually what I'm trying to do is to decode simple POINT geoms...
>>
>> This is what I've done in PHP (using the astext() approach)
>>
>>       // extract the geometry
>>       $geometry = str_replace("POINT(","", $loc);
>>       $geometry = str_replace(")","",$geometry);
>>       $coordinate = explode(" ",$geometry);
>>       $lon=$coordinate[0];
>>       $lat=$coordinate[1];
>>
>> Now this was for the web interface... ( the user can wait another 100ms or
>> so ... :] )
>> As far as a server solution is concerned this *is* a time-consuming
>> procedure... especially so when you've got *thousands* of connections per
>> minute...
>>
>> Furthermore, I'm developing the "beast" in Qt4 and - *ahem* - had never
>> needed to use libpq so I'm a bit lost here... :)
>>
>> Could someone be so kind as to point to a code example (outside using
>> astext() method) ? :]
>>
>> P.S. @John - found this to be interesting as I could store it in QByteArray
>> and go from there... ;) -- the real question here is: how to interpret the
>> byte array?
>>
>> BR,
>> Pedro.
>>
>>
>> On 11/23/2009 09:50 PM, Paul Ramsey wrote:
>>      
>>> That depends entirely on what you're planning to do with them once you
>>> get them. You'll probably want to serialize them into a known form so
>>> you can use them on the client side. ST_AsText() is one, very heavy,
>>> option. Mapserver, to take an example, uses
>>> encode(ST_AsBinary(ST_Force2D(geom)), 'hex'), so what goes over the
>>> wire is hex strings, but those are easy to turn into binary arrays, in
>>> WKB format, suitable for reading by a number of C++ libraries (like
>>> OGR or GEOG or etc).
>>>
>>> Best,
>>>
>>> P.
>>>
>>> On Mon, Nov 23, 2009 at 1:19 PM, Pedro Doria Meunier
>>> <pdoria at netmadeira.com>    wrote:
>>>
>>>        
>>>> Hi All,
>>>>
>>>> First off sorry for cross-posting. I'm hoping for a bigger audience... :]
>>>>
>>>> As for my question:
>>>>
>>>> How does one deal with Postgis geom fields in C++ ?
>>>> Google hasn't offered much help so far.
>>>>
>>>> I know I can make a "SELECT astext(my_geom) FROM my_table" and after
>>>> parsing
>>>> the resulting text.
>>>> This seems a bit awkward and time-consuming...
>>>>
>>>> Is there a better way to deal with it?
>>>>
>>>> Already thankful for any ideas,
>>>> BR,
>>>> Pedro.
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>>>>
>>>>
>>>>          
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