This page contains the specification for the DuckLake format, version 0.3.

Building Blocks

DuckLake requires two main components:

• Catalog database: DuckLake requires a database that supports transactions and primary key constraints as defined by the SQL-92 standard.
• Data storage: The DuckLake specification requires a storage component for storing the data in Parquet format.

Catalog Database

DuckLake uses SQL tables and queries to define the catalog information (metadata, statistics, etc.). This specification explains the schema and semantics of these:

• Data Types
• Queries
• Tables

If you are reading this specification for the first time, we recommend starting with the “Queries” page, which introduces the queries used by DuckLake.

Data Storage

DuckLake uses Parquet files to represent its tables. These files can be stored in object storage (blob storage), block storage or file storage.