Might be overkill unless you're looking to do semantic search. I've thought about what a search DSL for code would look like, it's challenging to embody a query

Might be overkill unless you're looking to do semantic search. I've thought about what a search DSL for code would look like, it's challenging to embody a query like "method which takes an Int64 and has a variable idx in it" into something compact and memorable. But a tokenizer seems like a good place to start, I think that's the right granularity for this kind of application. You'd want to do some chunking so that foo.bar doesn't find every foo and every bar, that sort of thing. Code search is, as the title says, a hard problem. But a language-aware token stream, the one you'd get from the lexer, is probably where one should start in building the database.