4 ms·

It's not how Riak does this, and it's not what's going on under the hood with Cassandra, either.

cbsmith 13y ago
Riak has something pretty close to this, and if your table in cassandra looked like: create bucket.users ( id uuid, username text, email text, phone text, primary key (uuid, username) ); That would be exactly how the data was encoded.
- iamaleksey 13y ago
  The difference is that all the cells with the same `id` would belong to the same partition and stored together, so you'd be able to write them atomically and read them together cheaply in a single operation. What marshray suggested would look like this: create table bucket.users (name text, field text, value text, primary key ((name, field))); - with a composite partition key. Then you'd have two separate single-cell partitions "jbellis:email" : "jbellis@example.com" and "jbellis:phone" : "555-5555". You don't want to do that in either Riak or Cassandra.
  - cbsmith 13y ago
    > What marshray suggested would look like this: create table bucket.users (name text, field text, value text, primary key ((name, field))); - with a composite partition key. Then you'd have two separate single-cell partitions "jbellis:email" : "jbellis@example.com" and "jbellis:phone" : "555-5555". You don't want to do that in either Riak or Cassandra. Ah I see what you mean. I thought the intent was to group by some unique ID for the user.
  - aphyr 13y ago
    you'd be able to write them atomically To clarify, this is only the case if you use Cassandra 2.0 transactions; normal batched writes are not atomic in the sense you're probably thinking.
    - iamaleksey 13y ago
      No batching here, just single-partition, two cell update. Atomic, but not isolated in the way you define isolation in your gist.
    - cbsmith 13y ago
      Actually, even in Cassandra 1.2, batch operations were atomic unless otherwise specified.
    - jeremiahjordan 13y ago
      They are atomic, they are not isolated. Those are two different properties. The "A" vs the "I" in ACID. http://en.wikipedia.org/wiki/ACID http://en.wikipedia.org/wiki/ACID Edit: Actually, they are isolated in the sense of ACID, doesn't matter what order you do to operations, the answer will be the same. But not isolated the way you want isolated described.
      - aphyr 13y ago
        No, they are not isolated in the sense of ACID. This behavior violates P0.
      - cbsmith 13y ago
        The scenario that he's found is when the two timestamps are actually identical. In that scenario, Cassandra cannot maintain its atomicity guarantee.

Riak has something pretty close to this, and if your table in cassandra looked like: create bucket.users ( id uuid, username text, email text, phone text, primary key (uuid, username) ); That would be exactly how the data was encoded.

iamaleksey 13y ago
The difference is that all the cells with the same `id` would belong to the same partition and stored together, so you'd be able to write them atomically and read them together cheaply in a single operation. What marshray suggested would look like this: create table bucket.users (name text, field text, value text, primary key ((name, field))); - with a composite partition key. Then you'd have two separate single-cell partitions "jbellis:email" : "jbellis@example.com" and "jbellis:phone" : "555-5555". You don't want to do that in either Riak or Cassandra.
- cbsmith 13y ago
  > What marshray suggested would look like this: create table bucket.users (name text, field text, value text, primary key ((name, field))); - with a composite partition key. Then you'd have two separate single-cell partitions "jbellis:email" : "jbellis@example.com" and "jbellis:phone" : "555-5555". You don't want to do that in either Riak or Cassandra. Ah I see what you mean. I thought the intent was to group by some unique ID for the user.
- aphyr 13y ago
  you'd be able to write them atomically To clarify, this is only the case if you use Cassandra 2.0 transactions; normal batched writes are not atomic in the sense you're probably thinking.
  - iamaleksey 13y ago
    No batching here, just single-partition, two cell update. Atomic, but not isolated in the way you define isolation in your gist.
  - cbsmith 13y ago
    Actually, even in Cassandra 1.2, batch operations were atomic unless otherwise specified.
  - jeremiahjordan 13y ago
    They are atomic, they are not isolated. Those are two different properties. The "A" vs the "I" in ACID. http://en.wikipedia.org/wiki/ACID http://en.wikipedia.org/wiki/ACID Edit: Actually, they are isolated in the sense of ACID, doesn't matter what order you do to operations, the answer will be the same. But not isolated the way you want isolated described.
    - aphyr 13y ago
      No, they are not isolated in the sense of ACID. This behavior violates P0.
    - cbsmith 13y ago
      The scenario that he's found is when the two timestamps are actually identical. In that scenario, Cassandra cannot maintain its atomicity guarantee.