You can't skip a datasource.
Due to slowness and accessibility, I'd suggest using extracts and make the data "more local" if you need to fix/improve this problem.
there are options.It all depends how the landscape has been setup.
- parallel query processing
- Configuring Parallel Queries in Tableau Server | Tableau Software
building a web interface and handling data and visualization.
please check the below links
- Tableau's Developer Tools & APIs
- Data Connectivity Tools & APIs | Tableau
- Leverage Tableau's getData() API feature to add commenting to your viz | Tableau Software
- Do more with APIs in Tableau 10, enter our hackathon | Tableau Software
--chain method calls
3.using python code and integrate tableau
- SQL Server Query to Tableau Data Extract LIKE A BOSS – Some more TDE API fun with Python & Tableau 8 | Ryan Robitaille
- Data extract API - sample code
- Tableau & Custom Python Scripts
- Leverage the power of Python in Tableau with TabPy | Tableau Software
4. initial sql and other options at tableau server level