Hi Nathan. Much of what you may be looking for (i.e. tables / fields used by Tableau) may be embedded within the workbook metadata, which is considered a BLOB object within the internal postgres table and by default the readonly user does not have read access to this.
There are a few alternatives though. For #1 and #2, see this link for more info. Metadata Automation
1. Leverage the twb auditor to load a set of workbooks and examine the output
2. Leverage the metadata automated solution
3. Work with your server admin to login to the db using an admin account and grant readonly access to pg_largeobject
4. Upvote this idea to provide readonly default access to pg_largeobject https://community.tableau.com/ideas/4667
Thanks Jeff. This helps a ton. I've upvoted the change to default access for readonly and am chasing that change with our IT team. The definitive placement of the data in question was a huge help. Thanks again...
I took a look at the Metadata Automation project and it looks pretty neat - but I'm guessing that I'll not have a lot of success getting that pushed through in the short term.