arangodb/Documentation/Books/AQL/examples-remove-vertex.md

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default	Deleting vertices with associated edges is currently not handled via AQL while the graph management interfaceand theREST API for the graph moduleoffer a vertex deletion functionality

Remove Vertex

Deleting vertices with associated edges is currently not handled via AQL while the graph management interface and the REST API for the graph module offer a vertex deletion functionality. However, as shown in this example based on the knows_graph, a query for this use case can be created.

When deleting vertex eve from the graph, we also want the edges eve -> alice and eve -> bob to be removed. The involved graph and its only edge collection has to be known. In this case it is the graph knows_graph and the edge collection knows.

This query will delete eve with its adjacent edges: {% aqlexample examplevar="examplevar" type="type" query="query" bind="bind" result="result" %} @startDocuBlockInline GRAPHTRAV_removeVertex1 @EXAMPLE_AQL{GRAPHTRAV_removeVertex1} @DATASET{knows_graph} LET edgeKeys = (FOR v, e IN 1..1 ANY 'persons/eve' GRAPH 'knows_graph' RETURN e._key) LET r = (FOR key IN edgeKeys REMOVE key IN knows) REMOVE 'eve' IN persons @END_EXAMPLE_AQL @endDocuBlock GRAPHTRAV_removeVertex1 {% endaqlexample %} {% include aqlexample.html id=examplevar query=query bind=bind result=result %} This query executed several actions:

• use a graph traversal of depth 1 to get the _key of eve's adjacent edges
• remove all of these edges from the knows collection
• remove vertex eve from the persons collection

The following query shows a different design to achieve the same result: {% aqlexample examplevar="examplevar" type="type" query="query" bind="bind" result="result" %} @startDocuBlockInline GRAPHTRAV_removeVertex2 @EXAMPLE_AQL{GRAPHTRAV_removeVertex2} @DATASET{knows_graph} LET edgeKeys = (FOR v, e IN 1..1 ANY 'persons/eve' GRAPH 'knows_graph' REMOVE e._key IN knows) REMOVE 'eve' IN persons @END_EXAMPLE_AQL @endDocuBlock GRAPHTRAV_removeVertex2 {% endaqlexample %} {% include aqlexample.html id=examplevar query=query bind=bind result=result %} Note: The query has to be adjusted to match a graph with multiple vertex/edge collections.

For example, the city graph contains several vertex collections - germanCity and frenchCity and several edge collections - french / german / international Highway.

To delete city Berlin all edge collections french / german / international Highway have to be considered. The REMOVE operation has to be applied on all edge collections with OPTIONS { ignoreErrors: true }. Not using this option will stop the query whenever a non existing key should be removed in a collection. {% aqlexample examplevar="examplevar" type="type" query="query" bind="bind" result="result" %} @startDocuBlockInline GRAPHTRAV_removeVertex3 @EXAMPLE_AQL{GRAPHTRAV_removeVertex3} @DATASET{routeplanner} LET edgeKeys = (FOR v, e IN 1..1 ANY 'germanCity/Berlin' GRAPH 'routeplanner' RETURN e._key) LET r = (FOR key IN edgeKeys REMOVE key IN internationalHighway OPTIONS { ignoreErrors: true } REMOVE key IN germanHighway OPTIONS { ignoreErrors: true } REMOVE key IN frenchHighway OPTIONS { ignoreErrors: true }) REMOVE 'Berlin' IN germanCity @END_EXAMPLE_AQL @endDocuBlock GRAPHTRAV_removeVertex3 {% endaqlexample %} {% include aqlexample.html id=examplevar query=query bind=bind result=result %}