If you specify a compound index, and then subsequently attempt to store a record in IDB and the value for that index is null, Safari >= 10.1 blows up with the error message below.
UnknownError – "An unknown error occurred within Indexed Database."
After this point the database is unusable. It still reports it self as open, but any subsequent calls (e.g., adding an item, opening a transaction) result in further errors.
This affects the iOS 10.3 beta as well. On Chrome and Firefox, and Safari < 10.1 there is no error.
db.version(1).stores({
friends: "++id,name,age,shoeSize,[name+shoeSize]"
});
// ...
// elsewhere in a transaction, this will except
db.friends.add({name: "Mark", age: 29, shoeSize: null});