[pgrouting-users] RAM needed by 'shortest' for planet database

[Tao Romera Martinez]

Stephen, Moi,

Thank you very much for your answers.
The problem actually got solved after a 'vacuum full' of the DB. It
was not a problem of insufficient RAM.
Nevertheless, the solution you proposed is very interesting and very
smart, so I keep it in mind for future services and products (as long
as you travel by car and are willing to take the highways, which is
not always the case, as in our latest release sweetway.zilapp.com).

Thank you to both of you for your help,

Tao

2013/3/7 Moi Lemien <hsylvio at gmail.com>:
> Le 25/02/2013 14:41, Stephen Woodbridge a écrit :
>
>> On 2/25/2013 4:22 AM, Tao Romera Martinez wrote:
>>>
>>> Hello,
>>>
>>> I am trying to run 'shortest' on a DB with the routing network of the
>>> whole planet. I have indices for the id, source, target and geom
>>> columns, and apply a window to limit the data I pass to 'shortest'.
>>> However, the postgres server crashes unless the source and target
>>> nodes are very close.
>>>
>>> I suspect the problem may come from a lack of RAM since the server
>>> only has 1GB, but still have not looked deeper into it. Has anyone
>>> put a server running with the whole planet routing network and
>>> experienced the same problem? How much memory is needed?
>>
>>
>> Yes, this sounds like a reason conclusion. pgRouting has to build a graph
>> in memory before it can solve it so loading very large numbers of vectors
>> into a graph will use a lot of memory. We use the Boost library to build and
>> solve the graph and it does not have any support for paging data into memory
>> as it is needed. Actually none of the other algorithms have that support
>> either.
>>
>> You might try something like:
>>
>> select edges from streets where near the startpoint
>> union
>> select edges from streets where near the endpoint
>> union
>> select edges from streets where highway only
>>
>> The idea here is to select all edges near the start and end points, where
>> "near" is a large enough radius to get you into the major roads part of the
>> network, and to only select the major roads network for the rest of the
>> graph. This would eliminate millions of neighborhood streets that you don't
>> car about.
>>
>> Turn the above into a query and pass that to you solution.
>>
>> -Steve
>> _______________________________________________
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>> Pgrouting-users at lists.osgeo.org
>> http://lists.osgeo.org/mailman/listinfo/pgrouting-users
>
>
> I was about to give quite the same answer as Stephen.
> Another thing you could do if the approach he proposed is not sufficient (or
> not adapted) is to use a part of the server's HDD for swapping.
>
> Regards,
> Sylvain.
>
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Tao Romera Martínez

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