A wrong cast led to numeric overflow for data files
greater than 4GB. The parallel repair assumed end of
file after reading the amount of data that the file
was bigger than 4GB. It truncated the data file and
noted the number of records it found so far in the
index file header as the number of rows in the table.
Removing the cast fixed the problem.
I added some cosmetic changes too.

The normal repair worked because it uses a different
function to read from the data file.