I recently found and fixed a bug in a site I was working on that resulted in millions of duplicate rows of data in a table that will be quite large even without them (still
I'd also recommend adding some constraints to your table to make sure that this doesn't happen to you again. A million rows, at 1000 per shot, will take 1000 repetitions of a script to complete. If the script runs once every 3.6 seconds you'll be done in an hour. No worries. Your clients are unlikely to notice.