Metadata
- Author: David Jayatillake
- Full Title:: The Bridge of Puppini
- Category:: 🗞️Articles
- URL:: https://davidsj.substack.com/p/the-bridge-of-puppini?triedRedirect=true
- Finished date:: 2024-07-31
Highlights
A typical star schema with a fact table joining many-to-one onto dimensional tables doesn’t usually cause an issue. However, as soon as the relationship between fact and dimension table changes from many-to-one to many-to-many (usually not allowed in semantic layers) or even one-to-many, fan-outs can become an issue. This is exacerbated by chains of joins. (View Highlight)
A Puppini bridge refers to a table in a database that is structured in a particular way - its purpose being to map join keys to one another. This is one part of the “Unified Star Schema”, a structure developed by Francesco Puppini. The idea is that the bridge table sits in the middle of the schema, and all other tables are joined to it directly. It takes some wrangling to create the bridge table, but once it is created, as long as you start your query with the bridge table and define aggregations against the bridge table itself, you can join to your heart’s content without worrying about having to define relationships or deal with chained joins. (View Highlight)