TOP PYSPARK INTERVIEW QUESTION 2023

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What is Apache Spark and how does it differ from Hadoop? What are the benefits of using Spark over MapReduce? What is a Spark RDD and what operations can be performed on it? How does Spark handle fault-tolerance and data consistency? Explain the difference between Spark transformations and actions. What is a Spark DataFrame and how is it different from an RDD? What is Spark SQL and how does it work? How can you optimize a Spark job to improve its performance? How does Spark handle memory management and garbage collection? Explain the role of Spark Driver and Executors. What is PySpark and how does it differ from Apache Spark? How do you create a SparkContext in PySpark? What is the purpose of SparkContext? What is RDD (Resilient Distributed Dataset)? How is it different from DataFrame and Dataset? What are the different ways to create RDD in PySpark? What is the use of persist() method in PySpark? How does it differ from cache() method? What is the use of broadcast variables in PySpark
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Hive failed renaming table with error "New location for this table already exist" ?

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How to rename a hive table without changing location?

If you got this type error :

 Execution Error, return code 1 from org.apache.hadoop.hive.ql.exec.DDLTask. Unable to alter table. New location for this table dbname.tablename already exists : hdfs://hanameservice/user/hive/warehouse/dbname.db/table name:

Ans :

Rename Table

ALTER TABLE table_name RENAME TO new_table_name;

 we can do that. You just need to follow below three commands in sequence.

  1. Lets say you have a external table test_1 in hive. And you want to rename it test_2 which should point test_2 location not test_1. Then you need to convert this table into Managed table using below command. test_1 -> pointing to test_1 location

    ALTER TABLE db_name.test_1 SET TBLPROPERTIES('EXTERNAL'='FALSE');

  2. Rename the table name.

    ALTER TABLE db_name.test_1 RENAME TO db_name.test_2;

  3. Again convert the managed table after renaming to external table.

    ALTER TABLE db_name.test_2 SET TBLPROPERTIES('EXTERNAL'='TRUE');

db_name.test_2 table will point the test_2 location. If we do it without making the managed table it will point the test_1 location.

 

Please comment and Query if you facing any issue .

 


 


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