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Apache Cassandra Operators
==========================

`Apache Cassandra <https://cassandra.apache.org/>`__ is an open source distributed NoSQL database that can be used when you need scalability and high availability without compromising performance. It offers linear scalability and fault-tolerance on commodity hardware or cloud infrastructure which makes it the perfect platform for mission-critical data. It supports multi-datacenter replication with lower latencies.

Prerequisite
------------

To use operators, you must configure a :doc:`Cassandra Connection <connections/cassandra>`.

.. _howto/operator:CassandraTableSensor:

Waiting for a Table to be created
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

The :class:`~airflow.providers.apache.cassandra.sensors.table.CassandraTableSensor` operator is used to check for the existence of a table in a Cassandra cluster.

Use the ``table`` parameter (set in ``default_args`` in the example below) to poke until the provided table is found. Use dot notation to target a specific keyspace.

.. _howto/operator:CassandraRecordSensor:

Waiting for a Record to be created
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

The :class:`~airflow.providers.apache.cassandra.sensors.record.CassandraRecordSensor` operator is used to check for the existence of a record of a table in the Cassandra cluster.

Use the ``table`` parameter (set in ``default_args`` in the example below) to mention the keyspace and table for the record. Use dot notation to target a specific keyspace.

Use the ``keys`` parameter to poke until the provided record is found. The existence of record is identified using key value pairs. In the given example, we're are looking for value ``v1`` in column ``p1`` and ``v2`` in column ``p2``.

Example use of these sensors
^^^^^^^^^^^^^^^^^^^^^^^^^^^^

.. exampleinclude:: /../../airflow/providers/apache/cassandra/example_dags/example_cassandra_dag.py
    :language: python
    :start-after: [START howto_operator_cassandra_sensors]
    :end-before: [END howto_operator_cassandra_sensors]

Reference
^^^^^^^^^

For further information, look at `Cassandra Query Language (CQL) SELECT statement <https://cassandra.apache.org/doc/latest/cql/dml.html#select>`_.