[postgis-users] segmentize lines with order

[Rémi Cura]

You don't need a stored procedure,
you can simply use pure sql with the CASE WHEN ... THEN .. WHEN .. THEN ..
.. END.

doc : http://www.postgresql.org/docs/9.3/static/functions-conditional.html

If you still need plpgsql :
http://www.postgresql.org/docs/9.3/static/plpgsql-control-structures.html#PLPGSQL-STATEMENTS-RETURNING

Cheers,
Rémi-C


2014-02-25 12:17 GMT+01:00 Pedro Costa <pedrocostaarma at sapo.pt>:

>  thanks Remi.
> I'm tying to make a stored procedure to use st_reverse when draw order is
> wrong.
> Now, my difficult is in writing the loop.
> I can't find something like that to guide me...
>
>
>
> Em 25-02-2014 11:11, Rémi Cura escreveu:
>
>   You can use
> http://postgis.refractions.net/docs/ST_Reverse.html
>
>  Or simply ORDER BY DESC for your path
>
>  Cheers,
>
>  Rémi-C
>
>
> 2014-02-25 11:49 GMT+01:00 Pedro Costa <pedrocostaarma at sapo.pt>:
>
>>  Hi Rémi,
>>
>> Thanks for your awnser.
>> My problem is that the draw order isn't equal in all lines so the path of
>> st_dumppoints sometimes return ascend order and another times descend. I
>> need to make a loop to make a reverse...
>>
>> Em 25-02-2014 08:33, Rémi Cura escreveu:
>>
>>    Hey,
>>  I don't understand your problem.
>>
>>  If you have multilinestring, you need to break it to linestring with an
>> id per multilinestring.
>>  If you have linestring, you just need to keep an id for each line and an
>> id per point (given in path).
>>
>>  Then you have several option to generate a ordered set of point (use the
>> ORDER BY and the row_number() postgres function).
>>
>>  If you give some detailled example maybe we could help better.
>>
>> Cheers,
>> Rémi-C
>>
>>
>> 2014-02-24 19:27 GMT+01:00 Stephen Woodbridge <woodbri at swoodbridge.com>:
>>
>>>  On 2/24/2014 11:33 AM, Pedro Costa wrote:
>>>
>>>> Hi guys,
>>>>
>>>> I'm trying to use lines from postgis to google maps android.
>>>> To do that, I'm converting the lines to points with St_DumpPoints and,
>>>> in gmaps, I make the lines. My problem is that I cannot create a correct
>>>> sequence to order the points in android and so i get wrong lines (see ss
>>>> atached). I'm already try to use st_dumpPoints path column and generate
>>>> a serial but doesn't result.
>>>>
>>>> Anybody knows a solution to resolve that?
>>>>
>>>
>>>  You probably need to write function that re-orients you lines before
>>> you dump them to points. The algorithm is like this:
>>>
>>> 1. for the first edge, if the start point match the the start or end of
>>> the 2nd edge, if it does then st_reverse() the first edge.
>>>
>>> 2. for the rest of the edges, if the edge point of the current edge
>>> matches the end point of the last edge, then st_reverse() the current edge.
>>>
>>> You might be able to st_union all the edges into one large edge and that
>>> should create a new reorder edge.
>>>
>>> No you can dump them and the order will be correct.
>>>
>>> -Steve
>>> _______________________________________________
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>>
>>
>>
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