The command "insert ignore into" in mysql can avoid interruptions caused by program errors when the id is repeated. In a certain situation, we need to remove duplicates from a lot of duplicated data through some rule, and hashmap can do the job. But it would be nice if the database could do it with a few memory.
I agree the point in the following post, but I cannot reply it. So I have to create a repeated topic.
There's never been infinity. Cantor's diagonal proof is completely wrong.