Cassandra - CqlEngine - using collection - collections

Question

I want to know how I can work with collection in cqlengine
I can insert value to list but just one value so I can't append some value to my list
I want to do this:
In CQL3:
UPDATE users
SET top_places = [ 'the shire' ] + top_places WHERE user_id = 'frodo';
In CqlEngine:
connection.setup(['127.0.0.1:9160'])
TestModel.create(id=1,field1 = [2])
this code will add 2 to my list but when I insert new value it replace by old value in list.
The only help in Cqlengine :
https://cqlengine.readthedocs.org/en/latest/topics/columns.html#collection-type-columns
And I want to know that how I can Read collection field by cqlengine.
Is it an dictionary in my django project? how I can use it?!!
Please help.
Thanks

Answer 1

Looking at your example it's a list.
Given a table based on the Cassandra CQL documentation:
CREATE TABLE plays (
id text PRIMARY KEY,
game text,
players int,
scores list<int>
)
You have to declare model like this:
class Plays(Model):
id = columns.Text(primary_key=True)
game = columns.Text()
players = columns.Integer()
scores = columns.List(columns.Integer())
You can create a new entry like this (omitting the code how to connect):
Plays.create(id = '123-afde', game = 'quake', players = 3, scores = [1, 2, 3])
Then to update the list of scores one does:
play = Plays.objects.filter(id = '123-afde').get()
play.scores.append(20) # <- this will add a new entry at the end of the list
play.save() # <- this will propagate the update to Cassandra - don't forget it
Now if you query your data with the CQL client you should see new values:
id | game | players | scores
----------+-------+---------+---------------
123-afde | quake | 3 | [1, 2, 3, 20]
To get the values in python you can simply use an index of an array:
print "Length is %(len)s and 3rd element is %(val)d" %\
{ "len" : len(play.scores), "val": play.scores[2] }