Udemy 10: What is Delta Lake?

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Questions and Answers

What is Delta Lake in terms of technology?

A database service

A proprietary technology

An open source technology (correct)

A storage format

What is the primary purpose of Delta Lake?

To replace databases

To create a new storage medium

To overcome limitations of data lakes (correct)

To provide a data warehouse

What is Lakehouse in the context of Delta Lake?

A storage format

A database service

A data warehouse

A platform that unifies data warehouse and advanced analytics (correct)

What is stored along with data files in Parquet format when creating a Delta Lake table?

A transaction log Signup and view all the answers

What is the primary function of the Delta Lake transaction log?

To serve as a single source of truth Signup and view all the answers

How are committed transactions recorded in Delta Lake?

In a JSON file Signup and view all the answers

What does the Delta Lake transaction log contain?

The operation performed, predicates, and affected files Signup and view all the answers

What happens to the original file when a writer process updates a record in Delta Lake?

A new copy of the file is created with the updates Signup and view all the answers

What is the main benefit of Delta Lake's transaction log in terms of read operations?

It ensures that the reader process always gets the most recent version of the data Signup and view all the answers

What happens when a writer process fails to write a file to Delta Lake due to an error?

The transaction log is not updated Signup and view all the answers

What is the purpose of the transaction log in terms of metadata?

It allows for scalable metadata Signup and view all the answers

What is the underlying file format used by Delta Lake?

Parquet and JSON Signup and view all the answers

What happens when a writer process writes a new file to Delta Lake?

It creates a new file and adds it to the transaction log. Signup and view all the answers

What is the purpose of the transaction log in terms of the reader process?

To provide the reader process with information about the latest files. Signup and view all the answers

What happens when a reader process reads a transaction log that has incomplete information?

It ignores the incomplete file and reads the previous files. Signup and view all the answers

How does Delta Lake handle updates to a file?

It creates a new file with the updated changes. Signup and view all the answers

What is the benefit of Delta Lake's transaction log in terms of scalability?

It enables simultaneous writer and reader processes. Signup and view all the answers

What is the advantage of using Delta Lake with Databricks?

It enables working with Data Lake in notebooks. Signup and view all the answers

What is the primary role of the Delta Lake transaction log in terms of data retrieval?

To ensure data consistency by tracking changes Signup and view all the answers

Which of the following best describes the relationship between Delta Lake and the Lakehouse architecture?

Delta Lake enables building Lakehouse architecture Signup and view all the answers

What is the primary benefit of using Delta Lake in terms of data storage?

Reliability and consistency in data lakes Signup and view all the answers

What is the purpose of the JSON file in the Delta Lake transaction log?

To record committed transactions Signup and view all the answers

What is the primary difference between Delta Lake and a traditional data warehouse?

Delta Lake is a storage layer, while data warehouses are a type of database service Signup and view all the answers

What is the role of Spark in the context of Delta Lake?

To check the transaction log for the most recent version of the data Signup and view all the answers

Study Notes

What is Delta Lake?

An open-source storage framework that brings reliability to data lakes.
Helps overcome limitations of data lakes, such as data inconsistency and performance issues.

Key Characteristics of Delta Lake

An open-source technology, not proprietary.
A storage framework or storage layer, not a storage format or storage medium.
Enables building lakehouse architecture, which unifies data warehouse and advanced analytics.

Delta Lake vs. Data Warehouse/Database

Delta Lake is not a data warehouse.
Delta Lake is not a database service.

How Delta Lake Works

Deployed on a cluster as part of the Databricks runtime.
Stores data in one or more data files in parquet format.
Stores a transaction log, known as Delta Log, which is an ordered record of every transaction performed on the table.
Transaction log serves as a single source of truth and is checked by Spark to retrieve the most recent version of data.

Transaction Log

Contains the operation performed, predicates, and affected files.
Each committed transaction is recorded in a JSON file.
Provides a full audit trail of all changes that have happened on the table.

Scenarios and Guarantees

Guarantees the most recent version of data is retrieved.
Read operation will never have a deadlock state or conflicts with ongoing operations.
Guarantees no dirty data is read, even in the event of errors or failures.

File Format

Underlying file format for Delta is parquet and JSON format.

Benefits of Delta Lake

Performs ACID transactions on data lakes.
Handles scalable metadata.
Provides a full audit trail of all changes.

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Description

Learn about Delta Lake, an open source storage framework that addresses data lakes' limitations, such as data inconsistency and performance issues. Understand how this technology helps overcome these challenges.