There are no published performance numbers for using SQLite because it is so slow I gave up the tests, deciding it was not even worth the effort. When I say slow, I mean 15+ hrs to do what even the basic SQL storage module on MySQL on MySQL could do in < 5 mins.
15+ hours vs 5 minutes ??!! i don't know the details of what the "what" is, but that's asounding.
This is most likely because a custom storage module for SQLite is needed, some have pointed this out. Probably not the answer you wanted, but thats about all there is.
if it's a factual answer that's saved me time/effort, i'm very appreciative! thanks. i think, then, i'll stick to dbm for spamassassin, and consider/evaluate use of sqlite for simple/short lookups in dovecot+exim. and/or wonder why bother ...