Hi!
That will always happen, folks always want to dump the entire DB.
That's fine, but the right way to do it is to download it from https://dumps.wikimedia.org/wikidatawiki/entities/, not send queries with syntax errors to the service :) Especially when it's 20M times the same query.
Also, fair warning, entire DB is big (about 80G as DB, no idea how much dumped, compressed dump is 7 G) so it may need some horsepower if you want to do non-trivial stuff with it. -- Stas Malyshev smalyshev@wikimedia.org