EF Core compiles a query for the entirety of the expression provided. I wonder if it actually outputs select * from book join author on book.author_id = author.

EF Core compiles a query for the entirety of the expression provided. I wonder if it actually outputs select * from book join author on book.author_id = author.id where author.id = 5 as you described - this seems like a pit of failure a framework would work hard to prevent from happening.