> With a large data set, :-) please give more detail: - How large? - and what is your real "business problem"? what type of network?
> I tried to use this http://blog.cleverelephant.ca/2010/07/network-walking-in-postgis.html in the PostGIS. As I see this is a directed "network graph", and I will try using the pgRouting tool - for a large graph! *( "pgRouting extends the PostGIS/PostgreSQL geospatial database to provide geospatial routing and other network analysis functionality." )* The pgRouting project did not exist in 2010/07 when this blogpost was written! [image: image.png] so I have adapted the example network ( from the original blogpost ) to pgRouting and this is my sample result ---------- ALL "downstream path" from "all deadends" sorted by descending cost --------- +------------+-----------+---------+-------------------------------------+--------------+ | route_cost | start_vid | end_vid | the_geom_text | edge_ids | +------------+-----------+---------+-------------------------------------+--------------+ | 6.24 | 3044 | 3000 | LINESTRING(4 4,3 4,2 3,1 2,1 1,0 0) | {13,9,6,3,1} | | 5.83 | 3043 | 3000 | *LINESTRING(4 3,4 2,3 2,2 1,1 1,0 0) | {12,8,5,2,1} |* | 4.83 | 3024 | 3000 | LINESTRING(2 4,2 3,1 2,1 1,0 0) | {10,6,3,1} | | 4.41 | 3014 | 3000 | LINESTRING(1 4,1 3,1 2,1 1,0 0) | {11,7,3,1} | | 3.41 | 3031 | 3000 | LINESTRING(3 1,2 1,1 1,0 0) | {4,2,1} | +------------+-----------+---------+-------------------------------------+--------------+ and the second line is same as in the blogpost ( *"Downstream(12)" *example) , just with an extra "deadends" points ; the edges :* {12,8,5,2,1} * start_vid : starting node/vertex id ( "deadends" in this example ) end_vid : ending node/vertex id constant 3000 (0,0) node/vertex id = 3000 + X*10+Y coordinate // ( 2,1 ) --> 3021 ; (0,0) --> 3000 > Whenever geospatial functions such as St_intersects or recursive query used, IMHO: A good scalable data model is extremely important. pgRouting has 2 important (separated) steps. - creating a routing topology - route optimized database ( with "start" - and "end" node/vertex ) - fast routing/graph/"network-walking" functions - without the geometry ( using Boost Graph c++ library ) ( in this example I have used https://docs.pgrouting.org/3.3/en/pgr_dijkstra.html ) and this is my adapted "routing" topology edge table : DROP TABLE IF EXISTS edge_table CASCADE; CREATE TABLE edge_table ( id bigint primary key, source bigint, target bigint, cost float, reverse_cost float, the_geom geometry ); -- network example from -- http://blog.cleverelephant.ca/2010/07/network-walking-in-postgis.html INSERT INTO edge_table VALUES( 1, 3011, 3000, 1, -1, 'LINESTRING(1 1, 0 0)'); INSERT INTO edge_table VALUES( 2, 3021, 3011, 1, -1, 'LINESTRING(2 1, 1 1)'); INSERT INTO edge_table VALUES( 3, 3012, 3011, 1, -1, 'LINESTRING(1 2, 1 1)'); INSERT INTO edge_table VALUES( 4, 3031, 3021, 1, -1, 'LINESTRING(3 1, 2 1)'); INSERT INTO edge_table VALUES( 5, 3032, 3021, 1, -1, 'LINESTRING(3 2, 2 1)'); INSERT INTO edge_table VALUES( 6, 3023, 3012, 1, -1, 'LINESTRING(2 3, 1 2)'); INSERT INTO edge_table VALUES( 7, 3013, 3012, 1, -1, 'LINESTRING(1 3, 1 2)'); INSERT INTO edge_table VALUES( 8, 3042, 3032, 1, -1, 'LINESTRING(4 2, 3 2)'); INSERT INTO edge_table VALUES( 9, 3034, 3023, 1, -1, 'LINESTRING(3 4, 2 3)'); INSERT INTO edge_table VALUES(10, 3024, 3023, 1, -1, 'LINESTRING(2 4, 2 3)'); INSERT INTO edge_table VALUES(11, 3014, 3013, 1, -1, 'LINESTRING(1 4, 1 3)'); INSERT INTO edge_table VALUES(12, 3043, 3042, 1, -1, 'LINESTRING(4 3, 4 2)'); INSERT INTO edge_table VALUES(13, 3044, 3034, 1, -1, 'LINESTRING(4 4, 3 4)'); full example code - with data&code: https://gist.github.com/ImreSamu/efda6093b67391a0edafff39d8056cb5 if you are interested in more examples.. check the pgRouting tutorial for example: *"Pre-processing waterways data"* https://workshop.pgrouting.org/2.7/en/un_sdg/sdg11-cities.html#pre-processing-waterways-data regards, Imre Shaozhong SHI <[email protected]> ezt írta (időpont: 2022. ápr. 22., P, 1:22): > Whenever geospatial functions such as St_intersects or recursive query > used, the PostGIS appears to spawn away to many child queries and just > obliterate the CPU. Nothing finishes. > > That forced me to try out to do the some tasks on the FME server. > > I tried to use this http://blog.cleverelephant.ca/2010/07/network > -walking-in-postgis.html in the PostGIS. > > I tried to linecombiner in FME. LineCombiner | FME (safe.com) > <https://www.safe.com/transformers/line-combiner/>. > > With a large data set, the running of processors were monitored. It was > estimated the PostGIS one would take 16 days to complete. > > But, it only took a few minute to do the same thing in FME. > > This suggests that something is not right with the PostGIS Server. > > Have anyone got experience with configuration and improving perfomance of > PostGIS Server? > > Regards, > > David > _______________________________________________ > postgis-users mailing list > [email protected] > https://lists.osgeo.org/mailman/listinfo/postgis-users >
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