Delta Format
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Category: Integration & Analytics
Summary: Open-source ACID table format (Delta Lake) used for all data stored in OneLake.
Overview
Delta format (Delta Lake) is an open-source storage format that adds ACID transactions, schema enforcement, and time-travel versioning on top of Parquet files. It is the standard table format used throughout Microsoft Fabric's OneLake, meaning data mirrored from Azure Cosmos DB (or processed by Apache Spark) is stored as Delta tables, enabling reliable, consistent reads across multiple engines (Spark, SQL, Power BI) without data duplication or format conversion.
More Info & Links
DP-420 Style Practice Questions
Q1. What capability does the Delta format add on top of Parquet files?
- A. ACID transactions, schema enforcement, and time-travel versioning
- B. Native support for the MongoDB query language
- C. Automatic partition key selection
- D. Built-in RU consumption metering
Q2. Why is the Delta format significant for data mirrored from Azure Cosmos DB into OneLake?
- A. It provides a consistent, open table format readable by multiple Fabric engines without conversion
- B. It encrypts the data using customer-managed keys automatically
- C. It reduces Azure Cosmos DB's transactional RU costs
- D. It enforces the container's partition key across Fabric
Answer Key
Answers are listed at the very end so you can attempt the questions first.
- Q1 (Delta Format): A. ACID transactions, schema enforcement, and time-travel versioning — Delta Lake (Delta format) extends Parquet with ACID transactions, schema enforcement, and versioning/time travel.
- Q2 (Delta Format): A. It provides a consistent, open table format readable by multiple Fabric engines without conversion — Storing mirrored data as Delta tables lets Spark, SQL, and Power BI all read the same consistent data without separate copies or conversions.
DP-420: Designing and Implementing Cloud-Native Applications Using Microsoft Azure Cosmos DB — term detail page
