You probably want to step away from the code editor and to the whiteboard, and understand what you are looking for from the data set. Look at the table names,

You probably want to step away from the code editor and to the whiteboard, and understand what you are looking for from the data set. Look at the table names, do they tell any story? Look at the constraints, look at the foreign keys. Do the attributes stand out in any way? Map it out and maybe you'll find a strategy. Then when you sit down you'll probably have a better idea what you're dealing with. I had to migrate big databases a couple times in my career and the db expert I worked with basically didn't even think about code for a week. We were like CSI agents trying to figure out wtf is going on.