mirror of https://gitee.com/bigwinds/arangodb
71 lines
3.0 KiB
Markdown
71 lines
3.0 KiB
Markdown
Remove Vertex
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=============
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Deleting vertices with associated edges is currently not handled via AQL while
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the [graph management interface](../../Manual/Graphs/GeneralGraphs/Management.html#remove-a-vertex)
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and the
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[REST API for the graph module](../../HTTP/Gharial/Vertices.html#remove-a-vertex)
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offer a vertex deletion functionality.
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However, as shown in this example based on the
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[knows_graph](../../Manual/Graphs/index.html#the-knowsgraph), a query for this
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use case can be created.
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When deleting vertex **eve** from the graph, we also want the edges
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`eve -> alice` and `eve -> bob` to be removed.
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The involved graph and its only edge collection has to be known. In this case it
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is the graph **knows_graph** and the edge collection **knows**.
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This query will delete **eve** with its adjacent edges:
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@startDocuBlockInline GRAPHTRAV_removeVertex1
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@EXAMPLE_AQL{GRAPHTRAV_removeVertex1}
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@DATASET{knows_graph}
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LET edgeKeys = (FOR v, e IN 1..1 ANY 'persons/eve' GRAPH 'knows_graph' RETURN e._key)
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LET r = (FOR key IN edgeKeys REMOVE key IN knows)
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REMOVE 'eve' IN persons
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@END_EXAMPLE_AQL
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@endDocuBlock GRAPHTRAV_removeVertex1
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This query executed several actions:
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* use a graph traversal of depth 1 to get the `_key` of **eve's** adjacent edges
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* remove all of these edges from the `knows` collection
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* remove vertex **eve** from the `persons` collection
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The following query shows a different design to achieve the same result:
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@startDocuBlockInline GRAPHTRAV_removeVertex2
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@EXAMPLE_AQL{GRAPHTRAV_removeVertex2}
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@DATASET{knows_graph}
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LET edgeKeys = (FOR v, e IN 1..1 ANY 'persons/eve' GRAPH 'knows_graph'
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REMOVE e._key IN knows)
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REMOVE 'eve' IN persons
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@END_EXAMPLE_AQL
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@endDocuBlock GRAPHTRAV_removeVertex2
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**Note**: The query has to be adjusted to match a graph with multiple vertex/edge collections.
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For example, the [city graph](../../Manual/Graphs/index.html#the-city-graph)
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contains several vertex collections - `germanCity` and `frenchCity` and several
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edge collections - `french / german / international Highway`.
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To delete city **Berlin** all edge collections `french / german / international Highway`
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have to be considered. The **REMOVE** operation has to be applied on all edge
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collections with `OPTIONS { ignoreErrors: true }`. Not using this option will stop the query
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whenever a non existing key should be removed in a collection.
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@startDocuBlockInline GRAPHTRAV_removeVertex3
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@EXAMPLE_AQL{GRAPHTRAV_removeVertex3}
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@DATASET{routeplanner}
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LET edgeKeys = (FOR v, e IN 1..1 ANY 'germanCity/Berlin' GRAPH 'routeplanner' RETURN e._key)
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LET r = (FOR key IN edgeKeys REMOVE key IN internationalHighway
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OPTIONS { ignoreErrors: true } REMOVE key IN germanHighway
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OPTIONS { ignoreErrors: true } REMOVE key IN frenchHighway
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OPTIONS { ignoreErrors: true })
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REMOVE 'Berlin' IN germanCity
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@END_EXAMPLE_AQL
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@endDocuBlock GRAPHTRAV_removeVertex3
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