I haven't seen an updated one as of late. 

But the data dictionary should be fairly up-to-date.  Workgroups Database

Here's an old pic from 2014.  Monitoring Tableau Server with readonly user | Data Visualization

I've been working on a way to help people write queries.  Take a look at my GitHub Project:

GitHub - isajediknight/Tableau-Server-Postgres-Queries: List of all Tableau Server Postgres DB Tables, Joins and Fields

this is not the ERD. But it may help.

Vizible Difference: Visualizing Data Dictionary