4.8 KiB
| layout | description |
|---|---|
| default | Our first example will locate the start vertex for a graph traversal via a geo index |
Combining Graph Traversals
Finding the start vertex via a geo query
Our first example will locate the start vertex for a graph traversal via a geo index. We use the city graph and its geo indices:
{% arangoshexample examplevar="examplevar" script="script" result="result" %}
@startDocuBlockInline COMBINING_GRAPH_01_create_graph
@EXAMPLE_ARANGOSH_OUTPUT{COMBINING_GRAPH_01_create_graph}
var examples = require("@arangodb/graph-examples/example-graph.js");
var g = examples.loadGraph("routeplanner");
~examples.dropGraph("routeplanner");
@END_EXAMPLE_ARANGOSH_OUTPUT
@endDocuBlock COMBINING_GRAPH_01_create_graph
{% endarangoshexample %}
{% include arangoshexample.html id=examplevar script=script result=result %}
We search all german cities in a range of 400 km around the ex-capital Bonn: Hamburg and Cologne.
We won't find Paris since its in the frenchCity collection.
{% aqlexample examplevar="examplevar" type="type" query="query" bind="bind" result="result" %}
@startDocuBlockInline COMBINING_GRAPH_02_show_geo
@EXAMPLE_AQL{COMBINING_GRAPH_02_show_geo}
@DATASET{routeplanner}
FOR startCity IN germanCity
FILTER GEO_DISTANCE(@bonn, startCity.geometry) < @radius
RETURN startCity._key
@BV {
bonn: [7.0998, 50.7340],
radius: 400000
}
@END_EXAMPLE_AQL
@endDocuBlock COMBINING_GRAPH_02_show_geo
{% endaqlexample %}
{% include aqlexample.html id=examplevar query=query bind=bind result=result %}
Lets revalidate that the geo indices are actually used:
{% aqlexample examplevar="examplevar" type="type" query="query" bind="bind" result="result" %}
@startDocuBlockInline COMBINING_GRAPH_03_explain_geo
@EXAMPLE_AQL{COMBINING_GRAPH_03_explain_geo}
@DATASET{routeplanner}
@EXPLAIN{TRUE}
FOR startCity IN germanCity
FILTER GEO_DISTANCE(@bonn, startCity.geometry) < @radius
RETURN startCity._key
@BV {
bonn: [7.0998, 50.7340],
radius: 400000
}
@END_EXAMPLE_AQL
@endDocuBlock COMBINING_GRAPH_03_explain_geo
{% endaqlexample %}
{% include aqlexample.html id=examplevar query=query bind=bind result=result %}
And now combine this with a graph traversal:
{% aqlexample examplevar="examplevar" type="type" query="query" bind="bind" result="result" %}
@startDocuBlockInline COMBINING_GRAPH_04_combine
@EXAMPLE_AQL{COMBINING_GRAPH_04_combine}
@DATASET{routeplanner}
FOR startCity IN germanCity
FILTER GEO_DISTANCE(@bonn, startCity.geometry) < @radius
FOR v, e, p IN 1..1 OUTBOUND startCity
GRAPH 'routeplanner'
RETURN {startcity: startCity._key, traversedCity: v._key}
@BV {
bonn: [7.0998, 50.7340],
radius: 400000
}
@END_EXAMPLE_AQL
@endDocuBlock COMBINING_GRAPH_04_combine
{% endaqlexample %}
{% include aqlexample.html id=examplevar query=query bind=bind result=result %}
The geo index query returns us startCity (Cologne and Hamburg) which we then use as starting point for our graph traversal.
For simplicity we only return their direct neighbours. We format the return result so we can see from which startCity the traversal came.
Alternatively we could use a LET statement with a subquery to group the traversals by their startCity efficiently:
{% aqlexample examplevar="examplevar" type="type" query="query" bind="bind" result="result" %}
@startDocuBlockInline COMBINING_GRAPH_05_combine_let
@EXAMPLE_AQL{COMBINING_GRAPH_05_combine_let}
@DATASET{routeplanner}
FOR startCity IN germanCity
FILTER GEO_DISTANCE(@bonn, startCity.geometry) < @radius
LET oneCity = (
FOR v, e, p IN 1..1 OUTBOUND startCity
GRAPH 'routeplanner' RETURN v._key
)
RETURN {startCity: startCity._key, connectedCities: oneCity}
@BV {
bonn: [7.0998, 50.7340],
radius: 400000
}
@END_EXAMPLE_AQL
@endDocuBlock COMBINING_GRAPH_05_combine_let
{% endaqlexample %}
{% include aqlexample.html id=examplevar query=query bind=bind result=result %}
Finally, we clean up again:
{% arangoshexample examplevar="examplevar" script="script" result="result" %}
@startDocuBlockInline COMBINING_GRAPH_06_cleanup
@EXAMPLE_ARANGOSH_OUTPUT{COMBINING_GRAPH_06_cleanup}
~var examples = require("@arangodb/graph-examples/example-graph.js");
~var g = examples.loadGraph("routeplanner");
examples.dropGraph("routeplanner");
@END_EXAMPLE_ARANGOSH_OUTPUT
@endDocuBlock COMBINING_GRAPH_06_cleanup
{% endarangoshexample %}
{% include arangoshexample.html id=examplevar script=script result=result %}