SmartGraph Management

    • General Graphs do not enforce or maintain any sharding of the collections and can therefore combine arbitrary sets of existing collections.
    • SmartGraphs enforce and rely on a special sharding of the underlying collections and hence can only work with collections that are created through the SmartGraph itself. This also means that SmartGraphs cannot be overlapping. A collection can either be sharded for one SmartGraph or for another. If you need to make sure that all queries can be executed with SmartGraph performance, just create one large SmartGraph covering everything and query it stating the subset of edge collections explicitly.

    To generally understand the concept of this module please read the chapter about General Graph Management first. In the following we will only describe the overloaded functionality. Everything else works identical in both modules.

    SmartGraphs also require edge relations to be created. The format of the relations is identical. The only difference is that all collections used within the relations to create a new SmartGraph must not exist yet. You have to let the SmartGraph module create the Graph collections for you, so that it can enforce the correct sharding.

    • graphName (string): Unique identifier of the graph
    • edgeDefinitions (array): List of relation definition objects, may be empty
    • orphanCollections (array): List of additional vertex collection names, may be empty
    • smartOptions (object): A JSON object having the following keys:
      • numberOfShards (number): The number of shards that will be created for each collection. To maintain the correct sharding all collections need an identical number of shards. This cannot be modified after creation of the graph.
      • smartGraphAttribute (string): The attribute that will be used for sharding. All vertices are required to have this attribute set and it has to be a string. Edges derive the attribute from their connected vertices.
      • isDisjoint (bool, optional): If set to true, a Disjoint SmartGraph will be created. This flag is not editable after creation. Default: false.

    The creation of a graph requires the name and some SmartGraph options. Due to the API edgeDefinitions and orphanCollections have to be given, but both can be empty arrays and be added later.

    The edgeDefinitions can be created using the convenience method _relation known from the general-graph module, which is also available here.

    orphanCollections again is just a list of additional vertex collections which are not yet connected via edges but should follow the same sharding to be connected later on.

    All collections used within the creation process are newly created. The process will fail if one of them already exists, unless they have the correct sharding already. All newly created collections will immediately be dropped again in the failure case.

    Examples

    Create a graph without relations. Edge definitions can be added later:

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    1. {[SmartGraph] 
    2. }

    Create a graph using an edge collection edges and a single vertex collection vertices as relation:

    1. arangosh> var graph_module = require("@arangodb/smart-graph");
    2. arangosh> var edgeDefinitions = [ graph_module._relation("edges", "vertices", "vertices") ];
    3. arangosh> var graph = graph_module._create("myGraph", edgeDefinitions, [], {smartGraphAttribute: "region", numberOfShards: 9});
    4. arangosh> graph_module._graph("myGraph");

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    1. {[SmartGraph] 
    2.   "edges" : [ArangoCollection 4010262, "edges" (type edge, status loaded)], 
    3.   "vertices" : [ArangoCollection 4010252, "vertices" (type document, status loaded)]

    Create a graph with edge definitions and orphan collections:

    1. arangosh> var graph_module = require("@arangodb/smart-graph");
    2. arangosh> var edgeDefinitions = [ graph_module._relation("myRelation", ["male", "female"], ["male", "female"]) ];
    4. arangosh> graph_module._graph("myGraph");

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    1. {[SmartGraph] 
    2.   "myRelation" : [ArangoCollection 4010308, "myRelation" (type edge, status loaded)], 
    3.   "female" : [ArangoCollection 4010306, "female" (type document, status loaded)], 
    4.   "male" : [ArangoCollection 4010307, "male" (type document, status loaded)], 
    5.   "sessions" : [ArangoCollection 4010296, "sessions" (type document, status loaded)] 
    6. }

    Modify a graph definition at runtime

    After you have created a SmartGraph its definition is not immutable. You can still add or remove relations. This is again identical to General Graphs.

    Remove a vertex collection from the graph:

    graph._removeVertexCollection(vertexCollectionName, dropCollection)

    • vertexCollectionName (string): Name of vertex collection.
    • dropCollection (bool, optional): If true the collection will be dropped if it is not used in any other graph. Default: false.

    In most cases this function works identically to the General Graph one. But there is one special case: The first vertex collection added to the graph (either orphan or within a relation) defines the sharding for all collections within the graph. They have their distributeShardsLike attribute set to the name of the initial collection. This collection can not be dropped as long as other collections follow its sharding (i.e. they need to be dropped first).

    Examples

    Create a SmartGraph and list its orphan collections:

    1. arangosh> var graph_module = require("@arangodb/smart-graph");
    2. arangosh> var relation = graph_module._relation("edges", "vertices", "vertices");
    3. arangosh> var graph = graph_module._create("myGraph", [relation], ["other"], {smartGraphAttribute: "region", numberOfShards: 9});
    4. arangosh> graph._orphanCollections();

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    Remove the orphan collection from the SmartGraph and drop the collection:

    1. arangosh> graph._removeVertexCollection("other", true);
    2. arangosh> graph_module._graph("myGraph");

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    1. {[SmartGraph] 
    2.   "edges" : [ArangoCollection 4010537, "edges" (type edge, status loaded)], 
    3.   "vertices" : [ArangoCollection 4010526, "vertices" (type document, status loaded)] 
    4. }

    Attempting to remove a non-orphan collection results in an error:

    1. arangosh> graph._removeVertexCollection("vertices");

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      You cannot drop the initial collection (vertices) as long as it defines the sharding for other collections (edges).

      1. arangosh> var graph_module = require("@arangodb/smart-graph");
      2. arangosh> var relation = graph_module._relation("edges", "vertices", "vertices");
      4. arangosh> graph._deleteEdgeDefinition("edges");
      5. arangosh> graph._removeVertexCollection("vertices");
      6. arangosh> db._drop("vertices");

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      1. [ArangoError 1485: Collection 'vertices' must not be dropped while '_to_edges', '_local_edges', '_from_edges', 'edges' have distributeShardsLike set to 'vertices'.]

      You may drop the complete graph, but remember to drop collections that you might have removed from the graph beforehand, as they will not be part of the graph definition anymore and thus not be dropped for you. Alternatively, you can truncate the graph if you just want to get rid of the data.

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      Delete an edge definition from the graph:

      graph._deleteEdgeDefinition(edgeCollectionName, dropCollection)

      • edgeCollectionName (string): Name of edge collection.
      • dropCollection (bool, optional): If true the collection will be dropped if it is not used in any other graph. Default: false.

      Examples

      Create a SmartGraph, then delete the edge definition and drop the edge collection:

      1. arangosh> var graph_module = require("@arangodb/smart-graph");
      2. arangosh> var relation = graph_module._relation("edges", "vertices", "vertices");
      3. arangosh> var graph = graph_module._create("myGraph", [relation], [], {smartGraphAttribute: "region", numberOfShards: 9});
      4. arangosh> graph._deleteEdgeDefinition("edges", true);
      5. arangosh> graph_module._graph("myGraph");

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      1. {[SmartGraph] 
      2.   "vertices" : [ArangoCollection 4010709, "vertices" (type document, status loaded)] 
      3. }

      It is allowed to remove the vertex collection vertices if it’s not used in any relation (i.e. after the deletion of the edge definition):

      1. arangosh> graph._deleteEdgeDefinition("edges");
      2. arangosh> graph._removeVertexCollection("vertices");

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      Keep in mind that you can not drop the vertices collection until no other collection references it anymore (distributeShardsLike collection property).

      Remove a SmartGraph:

      graph_module._drop(graphName, dropCollections)

      • graphName (string): Name of the Graph.
      • dropCollections (bool, optional): Define if collections should be dropped. Default: false.

      Examples

      Delete a SmartGraph and drop its collections:

      1. arangosh> graph_module._drop("myGraph", true);

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      Note that removing a Graph with the option to drop the collections fails if you removed collections from the Graph but did not drop these collections. This is because their distributeShardsLike attribute still references collections that are part of the Graph. Dropping collections while others point to them in this way is not allowed. Make sure to drop the referencing collections first.

      1. arangosh> graph._removeVertexCollection("other");

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      1. [ArangoError 1485: Collection 'vertices' must not be dropped while 'other' has distributeShardsLike set to 'vertices'.]