(Delta) Ch4 Delta Lake Table Operations
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Questions and Answers

What happens to removed data files when a DELETE operation is performed on a Delta table?

  • They are removed from the current version of the Delta table but not physically deleted. (correct)
  • They are added to a new version of the Delta table.
  • They are physically deleted immediately.
  • They are moved to a backup storage.

    • What type of operation does the MERGE operation in Delta Lake perform?

  • Only DELETE operation
  • Only UPDATE operation
  • Only INSERT operation
  • A mix of UPDATE, DELETE, and INSERT operations (correct)

    • What is the purpose of not physically deleting removed data files immediately?

  • To allow reverting to an older version of the table with time travel (correct)
  • To improve data loading performance
  • To prevent data loss
  • To free up storage space

    • What is the result of running an UPDATE operation on a Delta table?

    <p>Data files are added and removed from the Delta table as required.</p> Signup and view all the answers

    What is the primary reason Delta Lake adds a transactional layer to classic data lakes?

    <p>To enable classic DML operations</p> Signup and view all the answers

    What is the main difference between a DELETE operation and a MERGE operation in Delta Lake?

    <p>DELETE removes data, while MERGE performs an upsert operation</p> Signup and view all the answers

    What is the result of joining a source and a target table in a MERGE operation?

    <p>The target table is updated based on the match condition</p> Signup and view all the answers

    What is the significance of time travel in the context of Delta Lake?

    <p>It allows you to revert to an older version of the table</p> Signup and view all the answers

    Match the following Delta Lake operations with their descriptions:

    <p>DELETE = Removes data files from the current version of the Delta table UPDATE = Adds and removes data files from the Delta table as required MERGE = Performs an 'upsert' operation on the Delta table INSERT = statement is used to add new rows of data into a table</p> Signup and view all the answers

    Match the following outcomes with the corresponding Delta Lake operations:

    <p>Records are removed from the Delta table = DELETE Data files are added and removed from the Delta table = UPDATE Data files are removed from the current version of the Delta table = DELETE An 'upsert' operation is performed on the Delta table = MERGE</p> Signup and view all the answers

    Match the following Delta Lake features with their purposes:

    <p>Transactional layer = Enables classic DML operations on Delta tables Time travel = Allows reverting to an older version of the Delta table MERGE operation = Performs an 'upsert' operation on the Delta table Chapter Initialization script = Creates a sample Delta table for demonstration</p> Signup and view all the answers

    Match the following Delta Lake operations with the effect on data files:

    <p>DELETE = Removes data files from the Delta table UPDATE = Adds and removes data files from the Delta table MERGE = Adds and removes data files from the Delta table INSERT = Adds new data files to the Delta table</p> Signup and view all the answers

    Match the following Delta Lake concepts with their characteristics:

    <p>Delta table = A table with a transactional layer Time travel = Reverting to an older version of the Delta table MERGE operation = A mix of UPDATE, DELETE, and INSERT operations Data file = A physical storage unit for Delta table data</p> Signup and view all the answers

    Match the following Delta Lake operations with the type of change they make to the table:

    <p>DELETE = Removes existing data UPDATE = Modifies existing data MERGE = Combines inserts, updates, and deletes INSERT = Adds new data</p> Signup and view all the answers

    Match the following Delta Lake features with their purposes:

    <p>Time Travel = Reverts to an older version of the table Transactional Layer = Adds classic DML operations to data lakes Data Files = Stores data in a Delta table MERGE Operation = Performs an 'upsert' operation</p> Signup and view all the answers

    Match the following Delta Lake concepts with their characteristics:

    <p>Delta Table = A table that supports DML operations Data Lake = A storage system that lacks transactions DML Operations = Classic operations like UPDATE, DELETE, and MERGE Chapter Initialization = A script that creates the YellowTaxis table</p> Signup and view all the answers

    Match the following outcomes with the corresponding Delta Lake operations:

    <p>Removes data files = DELETE Adds and removes data files = UPDATE Performs an 'upsert' operation = MERGE Creates a new version of the table = INSERT</p> Signup and view all the answers

    Match the following Delta Lake operations with their types of changes:

    <p>DELETE = Removes data from the table UPDATE = Modifies existing data in the table MERGE = Combines data from source and target tables INSERT = Adds new data to the table</p> Signup and view all the answers

    Match the following Delta Lake operations with their use cases:

    <p>DELETE = Removing unwanted data UPDATE = Correcting existing data MERGE = Combining data from multiple sources INSERT = Adding new data to the table</p> Signup and view all the answers

    A DELETE operation on a Delta table only removes data files that are no longer needed.

    <p>False</p> Signup and view all the answers

    The MERGE operation in Delta Lake performs an 'upsert' operation, which is a mix of INSERT and DELETE operations.

    <p>False</p> Signup and view all the answers

    Data files are never removed from a Delta table when an UPDATE operation is performed.

    <p>False</p> Signup and view all the answers

    Time travel in Delta Lake allows you to revert to a newer version of a table.

    <p>False</p> Signup and view all the answers

    Delta Lake adds a transactional layer to classic data lakes to prevent data loss during updates.

    <p>True</p> Signup and view all the answers

    Study Notes

    Delta Lake DML Operations

    • Delta Lake adds a transactional layer to classic data lakes, enabling classic DML operations like updates, deletes, and merges.

    Deleting Data from a Delta Table

    • When performing a DELETE operation on a Delta table, the operation is performed at the data file level, removing and adding data files as needed.
    • Removed data files are not physically deleted immediately, allowing for time travel to revert to an older version of the table.

    Updating Data in a Delta Table

    • UPDATE operations also work at the data file level, adding and removing data files as required.

    Merging Data in a Delta Table

    • The MERGE operation is the most powerful Delta Lake DML operation, allowing for "upsert" operations (a mix of UPDATE, DELETE, and INSERT operations).
    • The MERGE operation joins a source and target table, writing a match condition to specify what happens with matching and non-matching records.

    Initializing the YellowTaxis Table

    • The YellowTaxis table is created by the "Chapter Initialization" script for Chapter 4.
    • The table has 9,999,995 million rows.

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    Related Documents

    Delta Lake Ch 4 Table Deletes, Updates, and Merges PDF

    Description

    Learn about performing DML operations like updates, deletes, and merges on Delta tables, and how they affect data files and versions.

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