Hoo boy. I did this once. Only it was CouchDB. And they didn’t use any schema. Data had accumulated in it for years. Then a customer said they wanted their data

Hoo boy. I did this once. Only it was CouchDB. And they didn’t use any schema. Data had accumulated in it for years. Then a customer said they wanted their data exported to PowerBI. I used a library that generated a type that could parse any JSON document you threw at it by feeding it examples. So I wrote some tools to scan through the database, generate parse test cases, etc. I then wrote a library to version and migrate records. With this I wrote some tools to start extracting meaningful bits out of the big-blob type. I could scan the database, download examples that didn’t work, make test cases, fix those, ask the experts in the system, etc. Then eventually it started spitting out structured data into Postgres and from there into PowerBI. Decent article.