A change introduced in
HPCC-17691 is causing the lazy opening mechanism for keyed index parts in a keyed join to be circumvented.
Prior to those changes, a index part would only be opened when a lookup was required. The change in
HPCC-17691 created the keyed managers for each part upfront and as a consequence the keyed manager opened the keys at initialization time.
This is not particularly significant in Thor unless the parts aren't eventually used, e.g. if the LHS is small (or 0 recs) and no actual lookups are required. It is also particularly noticeable if the keyed join is being performed against a super index with a lot of parts in total.