I want to search my project source code

I have a lot of code -- millions of lines at this point, written
over the last 5 years. Everything is in a bunch of nested folders.

At least once a week, I want to find some code that uses a few modules,
so I have to launch a find + grep at the top of the tree and then wait
for it to finish.

I wonder if I could store our source code in a postgresql table and
then use full text searching to index. Then I hope I could run a query
where I ask for all files that use modules X, Y, and Z.

I'm looking for something sort of like the locate utility, except that
instead of building a quickly-searchable list of file names, I want to
be able to search file contents also.

Matt