Hadoop Developer Interview Questions and Answers

Ingest CSV file to Spark dataframe and write to Hive table.

• Create SparkSession object

• Read CSV file using SparkSession.read.csv() method

• Create a dataframe from the CSV file

• Create a Hive table using SparkSession.sql() method

• Write the dataframe to the Hive table using dataframe.write.saveAsTable() method

Spark architecture, lazy evaluation, repartition vs coalesce

• Spark architecture consists of a driver program, cluster manager, and worker nodes

• Lazy evaluation is a feature of Spark where transformations are not executed until an action is called

• Repartition function shuffles data across partitions while coalesce reduces the number of partitions

• Repartition can increase or decrease the number of partitions while coalesce only decreases

• Repartition is a costly operation while coale...read more

MapReduce is a programming model and software framework for processing large amounts of data in parallel on a cluster.

• MapReduce is used for distributed processing of big data

• It consists of two phases: Map and Reduce

• Map phase processes input data and produces intermediate key-value pairs

• Reduce phase takes the output of the Map phase and combines the values for each key

• MapReduce is fault-tolerant and highly scalable

• Example: Word count program in MapReduce

Managed tables are physically stored in Hive's warehouse directory while external tables are not.

• Managed tables are created and managed by Hive while external tables are created outside of Hive.

• Managed tables are physically stored in Hive's warehouse directory while external tables are not.

• Managed tables are deleted when the table is dropped while external tables are not.

• Managed tables are used for internal purposes while external tables are used for external purposes.

• Example...read more

Hive architecture, table types, file formats, and dynamic partitioning.

• Hive architecture consists of metastore, driver, compiler, and execution engine.

• Hive tables can be of two types: managed tables and external tables.

• File formats supported by Hive include text, sequence, ORC, and Parquet.

• Dynamic partitioning allows automatic creation of partitions based on data.

Top command is a Linux utility that displays the system's processes in real-time.

• Displays the processes running on the system

• Updates the list of processes in real-time

• Provides information on CPU usage, memory usage, and process IDs

• Can be used to monitor system performance and identify resource-intensive processes

The question is about joins, window functions, partition vs colsec, and performance optimization techniques in Spark.

• Joins in Spark can be performed using various methods such as broadcast join, shuffle join, and sort-merge join.

• Window functions in Spark allow us to perform calculations across a group of rows that are related to the current row.

• Partitioning in Spark can be done based on columns or keys, and it affects the performance of operations such as joins and aggregatio...read more