Question

I’m using datamapper to store a lot of nokogiri-scraped data to rows

This set of data is always changing weekly, and occasionally I want to give the user the ability to “purge posts” so they can re-acquire new data.

Inside the method of post ‘/purge’ do (sinatra) I have the following

Post.all.destroy

The problem is it leaves the key at the auto-incremented amount. While this set of data is associated with other tables, that other data is also being cleared out as well, so I know the keys will have no problem matching. Each purge, my keys are getting huge (40,000) after some period of time though.

The reason that I don’t use DataMapper.auto_migrage! is because there is one particular table (with no associations) that I don’t want to touch (the Settings table).

PS. I tagged activerecord even though I’m using datamapper because i assume the process is very similar, just syntactically different.

Answer 1

The responsibility for AUTO INCREMENT values belongs to the DB engine, not to the ORM. So, if you want to reset its value, you have to issue a query like:

ALTER TABLE theTableInQuestion AUTO_INCREMENT=desired_value

Probably you will have something like:

adapter = DataMapper.repository(:default).adapter
adapter.execute('ALTER TABLE theTableInQuestion AUTO_INCREMENT= ? ', desired_value);