Parallelism or PLINQ with Postgres and Npgsql

Question

I have a Posrgres 9.04 database table with over 12,000,000 rows.

I need a program to read each row, do some calculations and lookups (against a 2nd table), then write a new row in a 3rd table with the results of these calculations. When done, the 3rd table will have the same number of rows as the 1st table.

Executing serially on a Core i7 720QM processor takes more than 24 hours. It only taxes one of my 8 cores (4 physical cores, but 8 visible to Windows 7 via HTT).

I want to speed this up with parallelism. I thought I could use PLINQ and Npgsql:

NpgsqlDataReader records = new NpgsqlCommand("SELECT * FROM table", conn).ExecuteReader();
var single_record = from row in records.AsParallel()
             select row;

However, I get an error for records.AsParallel(): Could not find an implementation of the query pattern for source type 'System.Linq.ParallelQuery'. 'Select' not found. Consider explicitly specifying the type of the range variable 'row'.

I've done a lot of Google searches, and I'm just coming up more confused. NpgsqlDataReader inherits from System.Data.Common.DbDataReader, which in turn implements IEnumerable, which has the AsParallel extension, so seems like the right stuff is in place to get this working?

It's not clear to me what I could even do to explicitly specify the type of the range variable. It appears that best practice is not to specify this.

I am open to switching to a DataSet, presuming that's PLINQ compatible, but would rather avoid if possible because of the 12,000,000 rows.

Is this even something achievable with Npgsql? Do I need to use Devart's dotConnect for PostgreSQL instead?

UPDATE: Just found http://social.msdn.microsoft.com/Forums/en-US/parallelextensions/thread/2f5ce226-c500-4899-a923-99285ace42ae, which led me to try this:

foreach(IDataRecord arrest in
            from row in arrests.AsParallel().Cast <IDataRecord>()
            select row)

So far no errors in the IDE, but is this a proper way of constructing this?