Answer:- CQL is Cassandra query language to access and query Apache distributed database. It consists of a CQL parser that incites all the implementation details to the server. The syntax of CQL is similar to SQL, but it does not alter the Cassandra data model.

Answer:- Compaction refers to a maintenance process in Cassandra, in which the SSTables are reorganized for data optimization of data structures on the disk. The compaction process is useful during interacting with memtables. There are two types of compaction in Cassandra. • Minor compaction: It gets started automatically when a new SSTable is created. Here, Cassandra condenses all the equally sized SSTables into one. • Major compaction: It is triggered manually using the nodetool. It compacts all SSTables of a column family into one.

Answer:- Unlike relational databases, Cassandra does not support ACID transactions.

Answer:- Cqlsh expands to Cassandra Query Language Shell that configures the CQL interactive terminal. It is a Python-based command-line prompt used on Linux or Windows and executes CQL commands like ASSUME, CAPTURE, CONSISTENCY, COPY, DESCRIBE, and many others. With cqlsh, users can define a schema, insert data, and execute a query.

Answer:- Cassandra Super Column is a unique element consisting of similar collections of data. They are actually key–value pairs with values as columns. It is a sorted array of columns, and they follow a hierarchy when in action: keystore > column family > super column > column data structure in JSON. Similar to the row keys, super column data entries contain no independent values but are used to collect other columns. It is interesting to note that super column keys appearing in different rows do not necessarily match and will not ever.

Answer:- • ALL: Highly consistent. A write must be written to a commitlog and a memtable on all replica nodes in the cluster. • EACH_QUORUM: A write must be written to a commitlog and a memtable on quorum of replica nodes in all data centers. • LOCAL_QUORUM: A write must be written to a commitlog and a memtable on quorum of replica nodes in the same center. • ONE: A write must be written to a commitlog and a memtable of at least one replica node. • TWO, Three: Same as One but with at least two and three replica nodes, respectively • LOCAL_ONE: A write must be written for at least one replica node in the local data center. • ANY • SERIAL: Linearizable consistency to prevent unconditional update • LOCAL_SERIAL: Same as serial but restricted to a local data center

Answer:- Both elements work on the principle of tuples having name and value. However, the former’s value is a string, while the value of the latter is a map of columns with different data types. Unlike Columns, Super Columns do not contain the third component of timestamp.

Answer:- As the name suggests, a column family refers to a structure having an infinite number of rows. Those are referred by a key–value pair, where the key is the name of the column and the value represents the column data. It is much similar to a hashmap in Java or a dictionary in Python. Rememeber, the rows are not limited to a predefined list of columns here. Also, the column family is absolutely flexible with one row having 100 columns while the other having only 2 columns.

Answer:- Source command is used to execute a file consisting of CQL statements.

Answer:- Thrift is a legacy RPC protocol or API unified with a code generation tool for CQL. The purpose of using Thrift in Cassandra is to facilitate access to the DB across the programming language.

Answer:- Tombstone is a row marker indicating a column deletion. These marked columns are deleted during compaction. Tombstones are of great significance as Cassandra supports eventual consistency, where the data must respond before any successful operation.

Answer:- Since Cassandra is a Java application, it can successfully run on any Java-driven platform or on Java Runtime Environment (JRE) or Java Virtual Machine (JVM). Cassandra also runs on Red Hat, CentOS, Debian, and Ubuntu Linux platforms.

Answer:- The default settings state that Cassandra uses 7000 port for Cluster Management, 9160 for Thrift Clients, and 8080 for JMX. These are all TCP ports and can be edited in the configuration file: bin/cassandra.in.sh

Answer:- Yes, but while doing that we need to keep in mind the following processes: • Do not forget to clear the commitlog with ‘nodetool drain’ • Turn off Cassandra to ensure that there is no data left in the commitlog • Delete the SSTable files for the removed CFs