> Cloud Spanner doesn't, however, support data manipulation language (DML) statements. DML includes SQL queries like INSERT and UPDATE. Instead, Spanner's interface definition includes RPCs for mutating rows given their primary key[21]. This is a bit annoying. You would expect a fully-featured SQL database to include DML statements.

Yes, I would expect that, and it does sound annoying. So, what is it about the INSERT and UPDATE that can't work given the other elements of Cloud Spanner's design?