Client CLI and commands

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Client CLI and commands

Cassandra CLI

Cassandra ships with a very basic interactive command line interface. Using the CLI you can connect to remote nodes in the cluster to create or update your schema and set and retrieve records.

Starting the CLI

You can start the CLI using the bin/cassandra-cli script in your Cassandra installation (bin\cassandra-cli.bat on windows). If you are evaluating a local cassandra node then be sure that it has been correctly configured and successfully started before starting the CLI.

If successful you will see output similar to this:

Welcome to cassandra CLI.

Type 'help;' or '?' for help. Type 'quit;' or 'exit;' to quit.

You must then specify a system to connect to:

connect localhost/9160;

Creating a Keyspace

We first create a keyspace to run our examples in.

create keyspace Twissandra;

Selecting the keyspace to user

We must then select our example keyspace as our new context before we can run any queries.

use Twissandra;

To Create A Column

We can then create a column to play with.

create column family User with comparator = UTF8Type;

For the later examples to work you must also update the schema using the following command. This will set the return type for the first and last name to make them human readable. It will also add and index for the age field so that you filter your gets using the Users name field.

update column family User with
        column_metadata =
        [
        {column_name: first, validation_class: UTF8Type},
        {column_name: last, validation_class: UTF8Type},
        {column_name: age, validation_class: UTF8Type, index_type: KEYS}
        ];

To Add Data

To add data we want to into our new column we must first specify our default key type otherwise we would have to specify it for each key using the format [utf8('keyname')] this is probably advisable if you have mixed key types but makes simple cases harder to read.

So we run the command below, which will last the length of you cli session. On quitting and restarting we must run it again.

assume User keys as utf8;

and then we add our data.

set User['jsmith']['first'] = 'John';
set User['jsmith']['last'] = 'Smith';
set User['jsmith']['age'] = '38';

If you get the error like this cannot parse 'John' as hex bytes, then it likely you either haven’t set your default key type or you haven’t updated your schema as in the create column example.

To Update Data

If we need to update a value we simply set it again.

set User['jsmith']['first'] = 'Jack';

To Get Data

Now let’s read back the jsmith row to see what it contains:

get User['jsmith'];

To Query Data

get User where age = '12';

For help

help;

To Quit

quit;

To Execute Script

bin/cassandra-cli -host localhost -port 9160 -f script.txt