Philip Greer <philip@tildesoftware.com> writes:
> WTF? Why would a vacuum be necessary in order for it to start using the index?
It's not the VACUUM that's necessary; it's the ANALYZE. The query
planner uses table statistics to make its decisions, and ANALYZE is
what collects those statistics. Without an ANALYZE the planner will
make default assumptions that are rarely correct. :)
VACUUM should also be run regularly, of course.
-Doug