mirror of https://gitee.com/bigwinds/arangodb
80 lines
3.4 KiB
Plaintext
80 lines
3.4 KiB
Plaintext
Combining Graph Traversals
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==========================
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### Finding the start vertex via a geo query
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Our first example will locate the start vertex for a graph traversal via [a geo index](../../Manual/Indexing/Geo.html).
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We use [the city graph](../../Manual/Graphs/index.html#the-city-graph) and its geo indices:
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@startDocuBlockInline COMBINING_GRAPH_01_create_graph
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@EXAMPLE_ARANGOSH_OUTPUT{COMBINING_GRAPH_01_create_graph}
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~addIgnoreCollection("germanHighway");
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~addIgnoreCollection("germanCity");
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~addIgnoreCollection("frenchHighway");
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~addIgnoreCollection("frenchCity");
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~addIgnoreCollection("internationalHighway");
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var examples = require("@arangodb/graph-examples/example-graph.js");
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var g = examples.loadGraph("routeplanner");
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var bonn=[50.7340, 7.0998];
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|db._query(`FOR startCity IN
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| WITHIN(germanCity, @lat, @long, @radius)
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| RETURN startCity`,
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| {lat: bonn[0], long: bonn[1], radius: 400000}
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).toArray()
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@END_EXAMPLE_ARANGOSH_OUTPUT
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@endDocuBlock COMBINING_GRAPH_01_create_graph
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We search all german cities in a range of 400 km around the ex-capital **Bonn**: **Hamburg** and **Cologne**.
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We won't find **Paris** since its in the `frenchCity` collection.
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@startDocuBlockInline COMBINING_GRAPH_02_combine
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@EXAMPLE_ARANGOSH_OUTPUT{COMBINING_GRAPH_02_combine}
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~var bonn=[50.7340, 7.0998]
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|db._query(`FOR startCity IN
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| WITHIN(germanCity, @lat, @long, @radius)
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| FOR v, e, p IN 1..1 OUTBOUND startCity
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| GRAPH 'routeplanner'
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| RETURN {startcity: startCity._key, traversedCity: v}`,
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|{
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| lat: bonn[0],
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| long: bonn[1],
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| radius: 400000
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} ).toArray()
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@END_EXAMPLE_ARANGOSH_OUTPUT
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@endDocuBlock COMBINING_GRAPH_02_combine
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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.
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Alternatively we could use a `LET` statement with a subquery to group the traversals by their `startCity` efficiently:
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@startDocuBlockInline COMBINING_GRAPH_03_combine_let
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@EXAMPLE_ARANGOSH_OUTPUT{COMBINING_GRAPH_03_combine_let}
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~var bonn=[50.7340, 7.0998];
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|db._query(`FOR startCity IN
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| WITHIN(germanCity, @lat, @long, @radius)
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| LET oneCity = (FOR v, e, p IN 1..1 OUTBOUND startCity
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| GRAPH 'routeplanner' RETURN v)
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| return {startCity: startCity._key, connectedCities: oneCity}`,
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|{
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| lat: bonn[0],
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| long: bonn[1],
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| radius: 400000
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} ).toArray();
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@END_EXAMPLE_ARANGOSH_OUTPUT
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@endDocuBlock COMBINING_GRAPH_03_combine_let
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Finally, we clean up again:
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@startDocuBlockInline COMBINING_GRAPH_04_cleanup
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@EXAMPLE_ARANGOSH_OUTPUT{COMBINING_GRAPH_04_cleanup}
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~var examples = require("@arangodb/graph-examples/example-graph.js");
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examples.dropGraph("routeplanner");
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~removeIgnoreCollection("germanHighway");
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~removeIgnoreCollection("germanCity");
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~removeIgnoreCollection("frenchHighway");
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~removeIgnoreCollection("frenchCity");
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~removeIgnoreCollection("internationalHighway");
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@END_EXAMPLE_ARANGOSH_OUTPUT
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@endDocuBlock COMBINING_GRAPH_04_cleanup
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