Bulbs: replacing create() with get_or_create()

Question

I am using TitanGraphDB + Cassandra.I am starting Titan as follows

cd titan-cassandra-0.3.1
bin/titan.sh config/titan-server-rexster.xml config/titan-server-cassandra.properties

I have a Rexster shell that I can use to communicate to Titan+Cassandra above.

cd rexster-console-2.3.0
bin/rexster-console.sh

I want to program the Titan Graph DB from my python program.I am using bulbs package for that.

from bulbs.titan import Graph

I want to replace my create() call with get_or_create()

I saw the following example on the web.

 james = g.vertices.create(name="James")

written as shown below.

 james = g.vertices.get_or_create('name',"James",{'name':'james')

Now my vertex create function is as follows.

self.g.vertices.create({ 'desc':desc,
                         'port_id':port_id,
                         'state':state,
                         'port_state':port_state,
                         'number':number,
                         'type':'port'} )

If I want to rewrite the above function call (create()) which takes multiple key-value pairs using get_or_create()

I first need to create a key.Or does it check all the attributes by default.

I am a beginner in python and I don't realy get the significance of
get_or_create('name',"James",{'name':'james')

why are function attributes specified like this.?

The function definition for get_or_create() is here

Any help will be appreciated.

Answer 1

The Bulbs 'get_or_create()' method looks up a vertex in the index and creates it if it doesn't exist. You can supply get_or_create() a Python dict of database properties the same way you can with create().

See...

• http://bulbflow.com/docs/api/bulbs/element/#vertex-proxy
• https://github.com/espeed/bulbs/blob/master/bulbs/element.py#L584

Here are a few examples...

>>> # a vertex where name is "James" doesn't exist so lookup() returns None
>>> g.vertices.index.lookup("name", "James")  
None

>>> # a vertex where name is "James" doesn't exist so a vertex is created
>>> data = dict(name="James", city="Dallas")
>>> james = g.vertices.get_or_create("name", "James", data)
>>> james.data()
{'city': 'Dallas', 'name': 'James'}

>>> james.eid   # returns the element ID for the james vertex    
>>> 1       

>>> # a vertex where name is "James" DOES exist so vertex is returned unmodified 
>>> data = dict(name="James", city="Dallas", age=35)
>>> james = g.vertices.get_or_create("name", "James", data)
>>> james.data()         # note age=35 was not added to the vertex properties
{'city': 'Dallas', 'name': 'James'}     

>>> # one way to update the vertex properities
>>> james.age = 35   
>>> james.save()

>>> james.data()
>>> {'city': 'Dallas', 'age': 35, 'name': 'James'}

>>> # a way to update the vertex properties if you only have the vertex ID
>>> # the vertex ID for the james vertex is 1
>>> data = dict(name="James", city="Dallas", age=35)
>>> g.vertices.update(1, data)           

>>> james = g.vertices.get(1)
>>> james.data()
>>> {'city': 'Dallas', 'age': 35, 'name': 'James'}