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I have been following the tutorial at https://anitagraser.com/2011/02/12/drive-time-isochrones/ in an attempt to create an isochrone map showing drive times to the nearest medical practice in my region (modifying my process where necessary for PgRouting v2.5).

Whilst calculating the drive time needed to reach each of my source nodes (in this case medical practices) from all other nodes, I found that all the cost values were returning as null except for the row following the source node (in the case of the screenshot, I would get a non-null result for row 3229 only).

Is there an obvious error in my code that would result in these null values?

Screenshot of sql query and response

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  • The function calls with parameter has_rcost are deprecated in current pgrouting. As you specify "false, false" (undirected, no rcost), does your osmlines table contain separate entries for both directions? Also the "one to many" calls of pgr_dijkstra should be more performant than the "one to one" form you use.
    – Redoute
    Commented Sep 16, 2017 at 14:42
  • The node id "3228::INT4" looks suspicious for me. Did you convert the bigint OSM IDs to smaller ids? This is no more necessary for pgrouting. Do source and target columns in osmlines contain the same converted IDs?
    – Redoute
    Commented Sep 16, 2017 at 14:50
  • Thanks - all valid points, I was using the 2.0 docs without realising! Still getting the issues when I strip it down to a one to one join so I think it's network topology errors. Will try with OS Open Roads rather than OSM to see if it makes any difference
    – hansolo
    Commented Sep 17, 2017 at 4:23

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