The most common way to access Cassandra is via the Thrift interface.
In short Thrift allows you easily setup service clients and servers in various programming languages. It generates code from a Thrift file describing the service. See Cassandra's Thrift file here.
Let's see how we can use a generated python client to access Cassandra.
- Install Thrift
- cd cassandra/interface
- thrift -gen py cassandra.thrift
- cd gen-py/gen-py/org/apache/cassandra
Run the script without arguments to get usage information:
Usage: ./Cassandra-remote [-h host:port] [-u url] [-f[ramed]] function [arg1 [arg2...]]
The following examples will use the following schema, specified in your `conf/storage-conf.xml`:
<Tables>
<Table Name = "users">
<ColumnFamily Index="Name">base_attributes</ColumnFamily>
<ColumnFamily Index="Name">extended_attributes</ColumnFamily>
<ColumnFamily ColumnType="Super" Index="Name">edges</ColumnFamily>
</Table>
</Tables>
insert
To get started, we'll insert some data into the `users` table:
> ./Cassandra-remote -h <hostname>:<ThriftPort> insert 'users' '1' 'base_attributes:email' 'ted@example.com' 0 None > ./Cassandra-remote -h <hostname>:<ThriftPort> insert 'users' '1' 'base_attributes:age' '25' 0 None > ./Cassandra-remote -h <hostname>:<ThriftPort> insert 'users' '1' 'edges:friends:2' '1' 0 None > ./Cassandra-remote -h <hostname>:<ThriftPort> insert 'users' '1' 'edges:friends:4' '1' 0 None > ./Cassandra-remote -h <hostname>:<ThriftPort> insert 'users' '1' 'edges:groups:1' '1' 0 None > ./Cassandra-remote -h <hostname>:<ThriftPort> insert 'users' '2' 'base_attributes:email' 'bill@example.com' 0 None
Note that the first two calls add data to the `email` and `age` columns in the `base_attributes` column family, while the third call adds data to the `2` column of the `friends` super column of the `edges` column family. Also note that I'm using a timestamp of 0 in all three cases. There are now two rows in this table, with key values of `1` and `2`.
get_slice
Not quite sure what's going on here, but clearly selects a set of columns from a specific column family. If you set `start` to a value less than 0, you get all of the columns, no matter what value you give `count`. If you set `start` to a value of zero or greater, setting `count` to `i` will return the first `i` columns. Returns a list of dicts, with the dicts containing `{columnName, value, timestamp}`.
Some examples on our table:
> ./Cassandra-remote -h <hostname>:<ThriftPort> get_slice 'users' '1' 'base_attributes' -1 0
[ {'columnName': 'email', 'value': 'ted@example.com', 'timestamp': 0},
{'columnName': 'age', 'value': '25', 'timestamp': 0}]
> ./Cassandra-remote -h <hostname>:<ThriftPort> get_slice 'users' '1' 'base_attributes' 0 1
[{'columnName': 'email', 'value': 'ted@example.com', 'timestamp': 0}]
> ./Cassandra-remote -h <hostname>:<ThriftPort> get_slice 'users' '1' 'base_attributes' 0 2
[ {'columnName': 'email', 'value': 'ted@example.com', 'timestamp': 0},
{'columnName': 'age', 'value': '25', 'timestamp': 0}]
get_column
Get a dict containing `{columnName, value, timestamp}` for a specific row.
Some examples on our table:
> ./Cassandra-remote -h <hostname>:<ThriftPort> get_column 'users' '1' 'base_attributes:age' {'columnName': 'age', 'value': '25', 'timestamp': 0}
> ./Cassandra-remote -h <hostname>:<ThriftPort> get_column 'users' '1' 'edges:friends:2' {'columnName': '2', 'value': '1', 'timestamp': 0}
get_column_count
Will tell you the number of columns for a particular row and column family.
An example on our table:
> ./Cassandra-remote -h <hostname>:<ThriftPort> get_column_count 'users' '1' 'base_attributes' 2
batch_insert
> ./Cassandra-remote -h <hostname>:<ThriftPort> batch_insert "batch_mutation_t({'table':'users', 'key':'3', 'cfmap': {'base_attributes': [column_t({'columnName': 'email', 'value': 'napoleon@example.com', 'timestamp': 0}), column_t({'columnName': 'age', 'value': '45', 'timestamp': 0}) ] } })"
None
batch_insert_blocking
remove
> ./Cassandra-remote -h <hostname>:<ThriftPort> remove 'users' '1' 'base_attributes:email'
None
> ./Cassandra-remote -h <hostname>:<ThriftPort> get_column 'users' '1' 'base_attributes:email'
{'columnName': 'email', 'value': '', 'timestamp': 0}
get_slice_super
> ./Cassandra-remote -h <hostname>:<ThriftPort> get_slice_super 'users' '1' 'edges' -1 0
[ {'name': 'friends', 'columns': [{'columnName': '2', 'value': '1', 'timestamp': 0}, {'columnName': '4', 'value': '1', 'timestamp': 0}]},
{'name': 'groups', 'columns': [{'columnName': '1', 'value': '1', 'timestamp': 0}]}]