key value stores for extendable objects

Question

http://www.infoq.com/presentations/newport-evolving-key-value-programming-model is a video about KV stores, and the whole premise is that redis promotes a column-based style for storing the attributes of an object under separate keys rather than serialising an object and storing it under a single key.

(This question is not redis-specific, but more a general style and best practice for KV stores in general.)

Instead of a blob for, say, a 'person', redis encourages a column based style where the attributes in an object are stored as separate key, e.g.

R.set("U:123:firstname","Billy")
R.set("U:123:surname","Newport")
...

I am curious if this is best practice, and if people take different approaches.

• E.g. you could 'pickle' an object under a single key. This has the advantage of being fetched or set in a single request

• Or a person could be a list with the first item being a field name index or such?

This got me thinking - I'd like a hierarchical key store, e.g.

R.set(["U:123","firstname"],"Billy")
R.set(["U:123","surname"],"Newport")
R.get(["U:123"]) returns [("firstname","Billy"),("surname","Newport")]

And then to add in transactions:

with(R.get(["U:132"]) as user):
  user.set("firstname","Paul")
  user.set("lastname","Simon")

From a scaling perspective, the batching of gets and sets is going to be important?

Are there key stores that do have support for this or have other applicable approaches?

Answer 1

You can get similar behavior in Redis by using an extra Set to keep track of the individual members of your object.

SET U:123:firstname Billy
SADD U:123:members firstname
SET U:123:surname Cobin
SADD U:123:members surname

GET U:123:firstname => Billy
GET U:123:firstname => Cobin
SORT U:123:members GET U:123:* -> [Billy, Cobin]
or
SMEMBERS U:123:members -> [firstname, surname]
MGET U:123:firstname U:123:firstname

Not a perfect match but good enough in many situations. There's an interesting article about how hurl uses this pattern with Redis