The Categories Type setting sets what type of categories are
being used, and how to optimize category searches. It set to one of:
Auto-detect
Automatically detect what kind of categories are being used at
search time, and optimize searches accordingly. This lets
non-overlapping categories (i.e. those whose pages do not occur in
any other category) be searched fastest, while still supporting
overlapping categories as fast as possible. This is the default
mode.
Overlapping
Assume that any category might overlap another. Category searches
will be slower than with the other modes. This mode was used
before the Categories Type setting existed. It can be set
as a fallback if the cached overlap data is believed to be
incorrect for some reason, e.g. category searches are wrong.
Non-overlapping
Assume that no category overlaps another. All category searches
will be as fast as the fastest Auto-detect mode search, but
searches for overlapping categories may not show all results.
This mode can be set to force higher-performance searches at the
potential expense of accuracy.
See the tips and performance caveats on the main Categories page
(here).
