UBB threads 7.2 missing index

We have a UBB threads 7.2 forum with more then 237.000 threads. Importing this forum into vb takes 'forever' on the thread table. The reason for that is, that impex does a ' SELECT importthreadid FROM thread WHERE importthreadid=XXX AND importforumid=1' before each insert,without an index on importthreadid. This means that mysql needs todo more then 237.000 table scans. That makes import unusable.

After creating an index on importthreadid, import time went down from 18 hours to 4 minutes.

Ronald