onyxfish/csvkit — pull request #204 by mattdudys (2013-03-04 02:41:13+00:00)
Title: Read csvgrep's matchfile into a set instead of a list for better lookup performance.

Tested with the following command which before, took over a few minutes (I ended up killing it, not sure how long it would take). After changing to using a set, it finishes in ~2 seconds for me:

csvgrep -c 1 -f /usr/share/dict/words /usr/share/dict/words