Optimizing Spark Program
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Questions and Answers

What is a recommended approach to improve performance when the same dataframe is being referred to in multiple places in a Spark program?

  • Increasing the size of the dataframe
  • Avoiding the use of dataframe caching
  • Running unnecessary Actions in the program
  • Using cache() or persist() functions (correct)
  • In a Spark program, what can be done to reduce shuffling when joining a big table with a small table?

  • Using additional Actions before the join
  • Partitioning the small table
  • Increasing the number of executors
  • Utilizing broadcast join (correct)
  • What will happen if unnecessary Actions are used in a Spark program?

  • Improves memory efficiency
  • Triggers unnecessary DAG execution (correct)
  • Optimizes the program automatically
  • Reduces CPU utilization
  • Which function in Spark is specifically used to store a dataframe at a user-defined storage level?

    <p>persist() function</p> Signup and view all the answers

    Why is it not recommended to run unnecessary Actions in Spark programs?

    <p>Because they trigger unnecessary DAG and execution from the beginning</p> Signup and view all the answers

    When does broadcast join tend to have less advantage over shuffle-based joins?

    <p>After crossing a certain threshold</p> Signup and view all the answers

    What is the major difference between the 'coalesce()' and 'repartition()' functions in Spark?

    <p>Coalesce() is used to decrease partitions while repartition() is used to increase partitions</p> Signup and view all the answers

    What technique can be used to eliminate data skewness issues in Spark?

    <p>Implementing the Salting Technique</p> Signup and view all the answers

    How does Spark optimize the logical plan internally for better performance?

    <p>By applying predicate pushdown for supported file formats</p> Signup and view all the answers

    When should you use the 'repartition()' function in Spark?

    <p>To increase the partitions for processing large data</p> Signup and view all the answers

    What is a common issue that can cause tasks to take longer in Spark?

    <p>Data skewness where data is unevenly distributed across partitions</p> Signup and view all the answers

    How does filtering data in earlier steps affect the performance of Spark applications?

    <p>It improves performance by reducing unnecessary processing</p> Signup and view all the answers

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