Storing nested JSON with Cassandra - json

Question

I am trying to store nested JSON object using composite tables in Cassandra and the nodejs bindings.
Let's say my data looks like this (friends and foes actually have more complex data structures than simple map):
{
id: 001,
name: 'luke',
lastname: 'skywalker',
friends: [
{ id: 002,
name: 'han',
lastname: 'solo' },
{ id: 003,
name: 'obiwan',
lastname: 'kenobi' },
{ id: 004,
name: 'leila',
lastname: 'skywalker' }
],
foes: [
{ id: 005,
name: 'dark',
lastname: 'vador' },
{ id: 006,
name: 'boba',
lastname: 'feet' }
]
}
From what I understood from composite keys (here: https://pkghosh.wordpress.com/2013/07/14/storing-nested-objects-in-cassandra-composite_columns/), I expected to store my data like this:
001 | luke | skywalker | friend:002:han:solo | friend:003:obiwan:kenobi | ... | foe:006:boba:feet
I created my table like this:
CREATE TABLE heroes (
id int,
name text,
lastname text,
friend_id int,
friend_name text,
friend_lastname text,
foe_id int,
foe_name text,
foe_lastname text,
PRIMARY KEY ((id, name, lastname), friend_id, foe_id)
);
And then run for each friends or foes:
client.execute(
'INSERT INTO heros (id, name, lastname, friend_id, friend_name, friend_lastname) VALUES (?, ?, ?, ?, ?)',
[001, 'luke', skywalker', 002, 'han', 'solo'],
function(err) {
//some code
}
)
Now, when runing the query 'SELECT * FROM heroes WHERE id=001' I expected to get only one row with all the friends or foes added as column.
Instead I get as many row as there as friends and foes. On top of this, a row for a friend looks like this:
{ rows:
[ { __columns: [Object],
id: 001,
name: 'luke',
lastname: 'skywalker',
friend_id: 002,
friend_name: 'han',
friend_lastname: 'solo',
foe_id: null,
foe_name: null,
foe_lastname: null } ],
meta:
// some data
}
I would have expected it not to have foe_* field at all.
Am I doing something wrong or is it the way cassandra handles composite items?

Answer 1

The result you are getting is be expected, because you have included friend and foes as part of the primary key. Hero has one to many association with friend and foe. In the blog post of mine that you are referring, I have used only the primary entity attributes as primary key. All the children entity attributes are mapped as dynamic columns.