如何使用现有集合(文档和边)创建图形

Question

我正在使用pyArango Python包创建几个集合(文档(顶点)和边)。如何使用现有的顶点和边以编程方式创建图形？我知道如何使用ArangoDB web界面“添加图形”来创建图形，但这需要一个繁琐的任务，因为有大量的集合。

Answer 1

在检查来自WebGui的网络流之后，我发现Add graph实际上是在发送一个以Edge和Document连接名称作为字符串输入的json post请求。因此，阻止我们使用现有边和文档的是pyarango中默认的验证构建

def _checkCollectionList(lst):
    for colName in lst:
        if not COL.isCollection(colName):
            raise ValueError("'%s' is not a defined Collection" % colName)

graphClass = GR.getGraphClass(name)

ed = []
for e in graphClass._edgeDefinitions:
    if not COL.isEdgeCollection(e.edgesCollection):
        raise ValueError("'%s' is not a defined Edge Collection" % e.edgesCollection)
    _checkCollectionList(e.fromCollections)
    _checkCollectionList(e.toCollections)

    ed.append(e.toJson())

_checkCollectionList(graphClass._orphanedCollections)

为了解决这个问题，我们只需要在创建图之前实现类。例如，我有两个文档集合people和department，我想创建一个图，其中：

• people -> knowns -> people
• people -> belongs_to -> ->

假设我的arangodb中已经有集合"people“、"department”、"knowns“、"belongs_to”，创建图的代码如下：

from pyArango.collection import Collection, Field
from pyArango.graph import Graph, EdgeDefinition

class knowns(Edges):
    pass

class belongs_to(Edges):
    pass

class people(Collection):
    pass

class department(Collection):
    pass

# Here's how you define a graph
class MyGraph(Graph) :
    _edgeDefinitions = [EdgeDefinition('knowns', ['people'], ['people']),
                        EdgeDefinition('belongs_to', ['people'], ['department'])]
    _orphanedCollections = []

theGraph = arrango_db.createGraph(name="MyGraph", createCollections=False)

请注意，类名与我传递到图形创建中的字符串完全相同。现在，我们已经在ArangoDB中创建了图形：

​

Answer 2

另一种解决方案是使用type动态创建类，这在已经定义了节点和边的情况下很有用

from pyArango.graph import Graph, EdgeDefinition
from pyArango.collection import Collection, Edges

# generate the class for "knowns", inheriting class "Edges", etc. 
_ = type("knowns", (Edges,), {}) 
_ = type("belongs_to", (Edges,), {}) 
_ = type("people", (Collection,), {})
_ = type("department", (Collection,), {})

# finally generate the class for the graph
_ = type(attribute+'Graph', (Graph,), 
        {"_edgeDefinitions" : [EdgeDefinition('knowns', ['people'], ['people']),
                    EdgeDefinition('belongs_to', ['people'], ['department'])],
        "_orphanedCollections" : []})

db.createGraph(name=MyGraph, createCollections=False)