Terminating graphlookup

[Conrad Mclean]

Hello All,

I'm pretty sure this is a NOOB question...

I have a series of origins and destinations... and need to get from point a to point b the quickest way...

eg.

a  to b

b to c

c to d

d to e

e to f

f to g

g to h

h to i

a to e

doing a graphlookup will give me two paths, the obvious a to i going thru all point and the a to i via a to e ... what I need to do however is terminate at g for example.. what are the routes from a to g... I have to know the dept to terminate using depth... i want to leverage Mongo to find the paths then look at depth to determine the shortest.  Thanks!

[Rupa Narayanan]

Conrad,

You should be able to achieve the shortest path using $graphlookup with 'restrictSearchWithMatch' to terminate at g , $sort on the depthField  and $project to display the fields needed. Please find provided below a sample query and also you might find this MongoDB blog on $graphlookup to find the shortest path helpful.

db.route.insert({"origin":  "a","destination":  "b"})
db.route.insert({"origin":  "b", "destination":  "c"})
db.route.insert({"origin":  "c", "destination":  "d"})
db.route.insert({"origin":  "d", "destination":  "e"})
db.route.insert({"origin":  "e", "destination":  "f"})
db.route.insert({"origin":  "f", "destination":  "g"})
db.route.insert({"origin":  "g","destination":  "h"})
db.route.insert({"origin":  "h","destination":  "i"})
db.route.insert({"origin":  "a", "destination":  "e"})




db.route.aggregate( [
   { $match:  { origin: { $eq: "a" } } },
    {
      $graphLookup: {
         from: "route",
         startWith: "$destination",
         connectFromField: "destination",
         connectToField: "origin",
         depthField: "numConnections",
         as: "traverseroute",
         restrictSearchWithMatch:{"destination":{"$ne":"h"}}
      }
   },         { $sort: { 'traverseroute.numConnections': 1 }},
              {  $project:  {"_id":0, "origin":1, "traverseroute.origin":1}}
   ])

This returns sorted result based on the traversed route

{ "origin" : "a", "traverseroute" : [ { "origin" : "f" }, { "origin" : "e" } ] }
{ "origin" : "a", "traverseroute" : [ { "origin" : "f" },  { "origin" : "e" },{ "origin" : "d" }, { "origin" : "c" }, { "origin" : "b" } ] }

Regards,

Rupa