Cassandra - Interview Questions and Answers

31) What do you mean by Cassandra-Cqlsh?

Cqlsh is a Cassandra query language shell used to execute the commands of CQL (Cassandra query language).

32) What are the differences between a node, a cluster, and datacenter in Cassandra?

Node: A node is a single machine running Cassandra.

Cluster: A cluster is a collection of nodes that contains similar types of data together.

Datacenter: A datacenter is a useful component when serving customers in different geographical areas. Different nodes of a cluster can be grouped into different data centers.

33) What is the use of Cassandra CQL collection?

Cassandra CQL collection is used to collect the data and store it in a column where each collection represents the same type of data. CQL consist of three types of types:

SET: It is a collection of unordered list of unique elements.
List: It is a collection of elements arranged in an order and can contain duplicate values.
MAP: It is a collection of unique elements in a form of key-value pair.

34) What is the use of Bloom Filter in Cassandra?

On a request of a data, before doing any disk I/O Bloom filter checks whether the requested data exist in the row of SSTable.

35) How does Cassandra delete data?

In Cassandra, to delete a row, it is required to associate the value of column to Tombstone (where Tombstone is a special value).

36) What is SuperColumn in Cassandra?

In Cassandra, SuperColumn is a unique element containing similar collection of data. They are actually key-value pairs with values as columns.

37) What is the difference between Column and SuperColumn?

Difference between Column and SuperColumn:

The values in columns are string while the values in SuperColumn are Map of Columns with different data types.
Unlike Columns, Super Columns do not contain the third component of timestamp.

38) What is Hadoop, HBase, Hive and Cassandra? Specify similarities and differences among them.

Hadoop, HBase, Hive and Cassandra all are Apache products.

Apache Hadoop supports file storage, grid compute processing via Map reduce. Apache Hive is a SQL like interface on the top of Haddop. Apache HBase follows column family storage built like Big Table. Apache Cassandra also follows column family storage built like Big Table with Dynamo topology and consistency.

39) What is the usage of "void close()" method?

In Cassandra, the void close() method is used to close the current session instance.

40) Which command is used to start the cqlsh prompt?

The cqlsh command is used to start the cqlsh prompt.

Interview :: Cassandra