CODEWITHSUNDEEP
database-designcassandracassandra-2.0
Mark
Mark

Reputation: 11740

Composite and non-composite columns in the same ColumnFamily?

I am working on my first project with the Cassandra database, and I'm trying to wrap my head around the data modelling. I am attempting to come up with a ColumnFamily definition that allows me to store some data that could be modelled (in C#) like this:

class the_data
{
    public string prop_1;
    public string prop_2;
    public Dictionary<string, Dictionary<string, List<string>>> other_data;
}

Now, the other_data can have its keys combined to create something like this:

public Dictionary<string, List<string>> other_data;

(where the key in this dictionary would be the combination of the two keys in the previous version).

I believe that I could model just this part of the data in Cassandra using a composite column, like so:

CREATE TABLE some_data
{
    row_key text,
    other_data_outer_key text,
    other_data_inner_key text,
    other_data_value text,
    PRIMARY KEY (row_key, other_data_outer_key, other_data_inner_key)
};

What I don't understand, however (or maybe it isn't possible), is how to have the composite column (because other_data_outer_key and other_data_inner_key become parts of the column name), as well as other columns that are NOT composite columns, nor duplicated for every combination of keys.

I'd like something like this:

CREATE TABLE some_data
{
    row_key text,                    <--- row key (partition key?)
    prop_1 text,                     <--- just a normal column (one per row) #1
    prop_2 text,                     <--- just a normal column (one per row) #2
    other_data_outer_key text,       <--- composite column name part 1
    other_data_inner_key text,       <--- composite column name part 2
    other_data_value text,           <--- composite column value
    PRIMARY KEY (row_key, other_data_outer_key, other_data_inner_key)
};

Is this possible? How can I accomplish this?

Upvotes: 1

Views: 155

Answers (1)

Adam Holmberg
Adam Holmberg

Reputation: 7365

Have a look at static columns: http://www.datastax.com/documentation/cql/3.1/cql/cql_reference/refStaticCol.html

This provides a way to store properties per partition in tables that have clustering columns.

Upvotes: 1

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