The performance issue with Postgres is only that expressions like:
string_row like 'foo%'
won't use the index on string_row if you've enabled locale support. The problem is that indexing this relies on being able to translate the "like" into roughly:
string_row between 'foo' and ('foo' || -the-biggest-character-)
unfortunately there's no simple way to know what "the biggest character" is if locale support is enabled.
Regular operations like "string_row = 'foo'" can use an index on string_row.
So for "normal" code, this isn't a big deal.
The current PG tree_sortkey implementation uses varying bitstrings and is fully indexed regardless of locale support. So I don't think enabling locale support will seriously impace the performance of an OpenACS 4.5/PG site.
