27 Questions
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.
What type of operation does the MERGE operation in Delta Lake perform?
A mix of UPDATE, DELETE, and INSERT operations
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
What is the result of running an UPDATE operation on a Delta table?
Data files are added and removed from the Delta table as required.
How many rows does the 'taxidb_YELLOWTaxis' table have?
9,999,995 rows
What is the primary reason Delta Lake adds a transactional layer to classic data lakes?
To enable classic DML operations
What happens to data files when an UPDATE operation is performed on a Delta table?
Data files are added and removed as needed
What is the main difference between a DELETE operation and a MERGE operation in Delta Lake?
DELETE removes data, while MERGE performs an upsert operation
What is the result of joining a source and a target table in a MERGE operation?
The target table is updated based on the match condition
What is the significance of time travel in the context of Delta Lake?
It allows you to revert to an older version of the table
Match the following Delta Lake operations with their descriptions:
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 = Not a DML operation supported by Delta Lake
Match the following outcomes with the corresponding Delta Lake operations:
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
Match the following Delta Lake features with their purposes:
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
Match the following Delta Lake operations with the effect on data files:
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
Match the following Delta Lake concepts with their characteristics:
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
Match the following Delta Lake operations with the type of change they make to the table:
DELETE = Removes existing data UPDATE = Modifies existing data MERGE = Combines inserts, updates, and deletes INSERT = Adds new data
Match the following Delta Lake features with their purposes:
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
Match the following Delta Lake concepts with their characteristics:
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
Match the following outcomes with the corresponding Delta Lake operations:
Removes data files = DELETE Adds and removes data files = UPDATE Performs an 'upsert' operation = MERGE Creates a new version of the table = INSERT
Match the following Delta Lake operations with their types of changes:
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
Match the following Delta Lake operations with their use cases:
DELETE = Removing unwanted data UPDATE = Correcting existing data MERGE = Combining data from multiple sources INSERT = Adding new data to the table
A DELETE operation on a Delta table only removes data files that are no longer needed.
False
The MERGE operation in Delta Lake performs an 'upsert' operation, which is a mix of INSERT and DELETE operations.
False
Data files are never removed from a Delta table when an UPDATE operation is performed.
False
The 'Chapter Initialization' script is used to create a clean taxidb.YellowTaxis table with 1 million rows.
False
Time travel in Delta Lake allows you to revert to a newer version of a table.
False
Delta Lake adds a transactional layer to classic data lakes to prevent data loss during updates.
True
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.
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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