[pgrouting-users] Calculating the shortest way between pairs

[Daniel Kastl]

On Sat, Mar 15, 2014 at 12:57 AM, Carsten Hogertz <carsten.hogertz at gmail.com
> wrote:

> puh, not the simplest task for a non-developer....I mean the function.
> to get a result with for one row is no problem (using whatever pg_*())
>

Of course you don't need to write a plpgsql function.
You can also make n queries with your programming language of your choice.
But with pgRouting it's common that you always need to code at least a
little bit.

Daniel






>
>
> 2014-03-14 16:33 GMT+01:00 Stephen Woodbridge <woodbri at swoodbridge.com>:
>
> Hi Carsten,
>>
>> I assume you can make a single pgRouting query from point A to B using
>> pgr_astar() or pgr_trsp() or something similar.
>>
>> Work that out first. Read the Documentation and the workshop.
>>
>> Then you just want to write a simple procedure to query your table and
>> for each row run the pgr_*() query and do something with the results.
>>
>> https://www.google.com/#newwindow=1&q=postgres%20plpgsql%20tutorial
>>
>> Read these to get a basic understanding ot plpgsql sripting for stored
>> procedures.
>>
>> If you table is big it will take a while. Get this working first and then
>> we can talk about how to speed it up if you need that.
>>
>> -Steve
>>
>>
>> On 3/14/2014 11:00 AM, Carsten Hogertz wrote:
>>
>>> lol. Now we're talking about the same issue!
>>> I could run n x n queries but this would not be very efficient as I'd
>>> like to have a more "automatic" solution.
>>>
>>> I already thought about function and looping but as being a complete
>>> newbie on looping and writing functions this seems quite hard to solve
>>> for myself.
>>>
>>> Maybe you've got a hint?
>>>
>>> thanks
>>> carsten
>>>
>>>
>>>
>>> 2014-03-14 15:53 GMT+01:00 Daniel Kastl <daniel at georepublic.de
>>> <mailto:daniel at georepublic.de>>:
>>>
>>>
>>>
>>>
>>>
>>>     On Fri, Mar 14, 2014 at 11:42 PM, Carsten Hogertz
>>>     <carsten.hogertz at gmail.com <mailto:carsten.hogertz at gmail.com>>
>>> wrote:
>>>
>>>         Hi Daniel,
>>>         thanks for your eMail.
>>>         Well, I think it's not a 1-n calculation. IMHO it's a 1-1
>>>         calculation,right?
>>>         So I don't know how to calculate the distance for each row of
>>>         the routing_pair table.
>>>
>>>
>>>     Well, you need to run this query for each row. So with n rows you
>>>     need n queries.
>>>     If you use standard shortest path function you need to run "n x n"
>>>     queries.
>>>
>>>     You may want to write a custom function, which makes first a select
>>>     of all records in your table and then loops through these records.
>>>     Or don't I still understand the problem?
>>>
>>>     Daniel
>>>
>>>
>>>
>>>
>>>         Thanks
>>>         Carsten
>>>
>>>
>>>         2014-03-14 15:33 GMT+01:00 Daniel Kastl <daniel at georepublic.de
>>>         <mailto:daniel at georepublic.de>>:
>>>
>>>
>>>
>>>
>>>
>>>             On Fri, Mar 14, 2014 at 11:26 PM, Carsten Hogertz
>>>             <carsten.hogertz at gmail.com
>>>             <mailto:carsten.hogertz at gmail.com>> wrote:
>>>
>>>                 Maybe to clearify.
>>>
>>>                 I've got the following two tables:
>>>
>>>                 Table at_2po_4pgr with the columns:
>>>
>>>                    id integer NOT NULL,
>>>                    osm_id bigint,
>>>                    osm_name character varying,
>>>                    osm_meta character varying,
>>>                    osm_source_id bigint,
>>>                    osm_target_id bigint,
>>>                    clazz integer,
>>>                    flags integer,
>>>                    source integer,
>>>                    target integer,
>>>                    km double precision,
>>>                    kmh integer,
>>>                    cost2 double precision,
>>>                    reverse_cost double precision,
>>>                    x1 double precision,
>>>                    y1 double precision,
>>>                    x2 double precision,
>>>                    y2 double precision,
>>>                    geom_way geometry(LineString,4326)
>>>
>>>                 and Table routing_pair with the columns:
>>>
>>>                    id integer,
>>>                    h_key integer,
>>>                    lat_htl double precision,
>>>                    lon_htl double precision,
>>>                    source integer,
>>>                    geom_htl geometry(Point,4326),
>>>                    lat_bhf double precision,
>>>                    lon_bhf double precision,
>>>                    target integer,
>>>                    geom_bhf geometry(Point,4326)
>>>
>>>
>>>                 The routing_pair table hold three important information:
>>>                 ID
>>>                 SOURCE
>>>                 TARGET
>>>
>>>                 All columns are filled (source + target are calculated
>>>                 from at_2po_4pgr.
>>>
>>>                 The task seems to be quite simple: I want for each row
>>>                 from the routing_pair the distance between soure +
>>>                 target (and if possible its geom).
>>>                 Could you please help me how to solve this?
>>>
>>>
>>>             Hi Carsten,
>>>
>>>             There is a function named kDijkstra and it allows you to
>>>             calculate all paths from one node to many:
>>>             http://docs.pgrouting.org/2.0/en/src/kdijkstra/doc/index.
>>> html#pgr-kdijkstra
>>>
>>>             If something is not clear with the page above, feel free to
>>> ask.
>>>
>>>             Daniel
>>>
>>>
>>>
>>>
>>>
>>>             --
>>>             Georepublic UG & Georepublic Japan
>>>             eMail: daniel.kastl at georepublic.de
>>>             <mailto:daniel.kastl at georepublic.de>
>>>
>>>             Web: http://georepublic.info
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