How Does Tableau Read/Import Data

Hello everyone,

I am looking to better understand the back-end processes in which Tableau imports data from live connections and data extracts, but have not been able to find much documentation. My current situation involves a 600 million record table with 30 columns. How would Tableau handle the import of such a large table? What are all of Tableau's back-end steps?

A few key questions. Please do not limit your response to just these, as I am really trying to understand what Tableau is doing behind the scenes.

1. At what point in development does Tableau begin reading data?
   1. Does it read all data once the connection is made, a sample of the data?
2. Does Tableau only read data when required (when a dimension or measure is used)?
3. What are all the instances in which a re-query is required (filter change, action, etc...)
   1. Does the re-query look at all the data or only relevant fields?

Any extra information or documentation is greatly appreciated!

Thank you,

Aaron