Value Lookup from File without Slurping

I agree on the database solution.
Database are the rigth tool to solve this kind of problem.
Only consider the start up cost of setting up the database. This could be a
very time consuming task if someone is not familiar with database
technology.

Using sqldf as mentioned previously on this thread allows one to use
the SQLite database with no setup at all.  sqldf automatically creates
the database, generates the record layout, loads the file (not going through
R but outside of R so R does not slow it down) and extracts the
portion you want into R issuing the appropriate calls to RSQLite/DBI and
destroying the database afterwards all automatically.  When you
install sqldf it automatically installs RSQLite and the SQLite database
itself so the entire installation is just one line: install.packages("sqldf")