Ask HN: Stock data question (again)

Hi everyone,

I posted a question a few days ago, but judging from the responses, I don't think I phrased my question properly.

I'm loonking to purchase historical stock and financial data that would cover every public company for the past 20 years or so.

For my purposes, querying a external source like yahoo for a single stock at a time would simply be way too slow. I would basically need to run mapreduce on the entire data set looking for certain patterns.

Does anyone know where I can purchase this type of data set? I'm guessing it tens of gigabytes in size.

Thanks