AFAIK, all of the common open-source databases have this problem. Postgres is better than mysql, but it still needs to do extensive locking when you alter a col

AFAIK, all of the common open-source databases have this problem. Postgres is better than mysql, but it still needs to do extensive locking when you alter a column. Under heavy read/write loads and/or with large tables, this can blow up in your face.