tf_graph_shortest_path | HEAVY.AI Documentation

Given a distance-weighted directed graph, consisting of a queryCURSOR input consisting of the starting and ending node for each edge and a distance, and a specified origin and destination node, tf_graph_shortest_path computes the shortest distance-weighted path through the graph between origin_node and destination_node, returning a row for each node along the computed shortest path, with the traversal-ordered index of that node and the cumulative distance from the origin_node to that node. If either origin_node or destination_node do not exist, an error is returned.

SELECT * FROM TABLE(
    tf_graph_shortest_path(
        edge_list => CURSOR(
            SELECT node1, node2, distance FROM table
        ),
        origin_node => <origin node>,
        destination_node => <destination node>
    )

Input Arguments

Parameter	Description	Data Types
`node1`	Origin node column in directed edge list CURSOR	Column< INT \| BIGINT \| TEXT ENCODED DICT>
`node2`	Destination node column in directed edge list CURSOR	Column< INT \| BIGINT \| TEXT ENCODED DICT> (must be the same type as `node1`)
`distance`	Distance between origin and destination node in directed edge list CURSOR	Column< INT \| BIGINT \| FLOAT \| DOUBLE >
`origin_node`	The origin node to start graph traversal from. If not a value present in `edge_list.node1`, will cause empty result set to be returned.	BIGINT \| TEXT ENCODED DICT
`destination_node`	The destination node to finish graph traversal at. If not a value present in `edge_list.node1`, will cause empty result set to be returned.	BIGINT \| TEXT ENCODED DICT

Output Columns

Name	Description	Data Types
`path_step`	The index of this node along the path traversal from `origin_node` to `destination_node`, with the first node (the `origin_node)` indexed as 1.	Column< INT >
`node`	The current node along the path traversal from `origin_node` to `destination_node`. The first node (as denoted by `path_step` = 1) will always be the input `origin_node`, and the final node (as denoted by `MAX(path_step)`) will always be the input `destination_node`.	Column < INT \| BIGINT \| TEXT ENCODED DICT> (same type as the `node1` and `node2` input columns)
`cume_distance`	The cumulative distance adding all input `distance` values from the `origin_node` to the current node.	Column < INT \| BIGINT \| FLOAT \| DOUBLE> (same type as the `distance` input column)

Example A

/* Compute the shortest flight route on United Airlines for the year 2008 as measured
by flight time between origin airport 'RDU' (Raleigh-Durham, NC) and destination 
airport 'SAT' (San Antonio, TX), adding 60 minutes for each leg to account for 
boarding/plane change time costs, and only counting routes that were flown at least
300 times during the year. */
 
SELECT
  *
FROM
  TABLE(
    tf_graph_shortest_path(
      edge_list => CURSOR(
        SELECT
          origin,
          dest,
          /* Add 60 minutes to each leg to account
          for boarding/plane change costs */
          AVG(airtime) + 60 as avg_airtime
        FROM
          flights_2008
        WHERE
          carrier_name = 'United Air Lines'
        GROUP by
          origin,
          dest
        HAVING
          COUNT(*) > 300
      ),
      origin_node => 'RDU',
      destination_node => 'SAT'
    )
  )
ORDER BY
  path_step
 
path_step|node|cume_distance
1|RDU|0
2|ORD|167
3|DEN|354
4|SAT|519

Example B

/* Compute the shortest path between along a time-traversal weighted
edge graph of roads in the Eastern United States between a location in North Carolina and
a location in Maine, joining to a node locations table to output the lon/lat pairs 
of each node. */
select
  path_step,
  node,
  lon,
  lat,
  cume_distance
from
  table(
    tf_graph_shortest_path(
      cursor(
        select
          node1,
          node2,
          traversal_time
        from
          usa_roads_east_time
      ),
      1561955,
      1591319
    )
  ),
  USA_roads_east_coords
where
  node = node_id 
order by 
  cume_distance desc
limit 20;
path_step|node|lon|lat|cume_distance
4380|1591319|-71.55136299999999|43.75256|13442017
4379|1591989|-71.55174099999999|43.75245|13441199
4378|1589348|-71.554147|43.752464|13436371
4377|2315795|-71.554867|43.752489|13434924
4376|1589286|-71.55497099999999|43.752113|13434214
4375|1589285|-71.555049|43.751833|13433685
4374|2315785|-71.555999|43.750704|13431238
4373|2315973|-71.55798799999999|43.748622|13426553
4372|2315950|-71.56366299999999|43.746268|13417798
4371|1589788|-71.56476599999999|43.745765|13416053
4370|1591997|-71.56484|43.745691|13415884
4369|1589787|-71.564886|43.745645|13415779
4368|2315951|-71.56517599999999|43.745353|13415113
4367|2315952|-71.56659499999999|43.744599|13412756
4366|1591999|-71.56685899999999|43.744565|13412397
4365|543394|-71.567357|43.744335|13411606
4364|543393|-71.567832|43.744116|13410852
4363|543392|-71.571827|43.743673|13405444
4362|541181|-71.57268499999999|43.743802|13404271
4361|1589786|-71.572964|43.743844|13403890

The computed shortest path along a time-traversal weighted road edge graph for the eastern US.