> So I need to either find an Index that will work with regexes or
> re-write my code to update each subdirectory separately and use simpler
> UPDATE statement for each.
Why don't you use a LTREE type to model your directory tree ? It's been
designed specifically for this purpose and has indexed regular expression
search.
http://www.sai.msu.su/~megera/postgres/gist/ltree/http://www.sai.msu.su/~megera/postgres/gist/
