SQLite - Time to build a database

I have a sqlite (version 3.6.13) database with 300000+ rows

1500 of these rows have faulty data.

So I read the main database row by row, tested the validity of one
column, and inserted the good rows into a new database.

This process took 27 minutes on a fairly recent desktop computer.
( about 10000 rows a minute or 170 a second ) 

I thought the whole process would take a few seconds, so I wonder if 27
minutes is a reasonable time for this database creation.

As the database was being created, I noticed a journal file was in use
though I haven't worked out what that did, yet.


TIA


Owen