switching between different databases - in 1.3.0.rc1

[Rob McEwen]

I was finally able to download and successfully install 1.3.0.rc1 on a 
testing Debian VM. And it worked!

For this first attempt - I installed LMDB as the database.  But the 
first thing that I found to be odd - is that my cursory testing of 
performance (although for just 1-at-a-time reads, these were just 
evaluations of emails, so - no writes) - that cursory testing showed 
LMDB to be actually a little SLOWER than than my 1.2.5 setup using the 
Berkeley database. That was a huge surprise! I had expected so much more 
from LMDB. And this was using the same hundreds of MBs large data files, 
and on similar hardware. Is that result - to be expected? Or should LMDB 
have been much faster? Nevertheless, I've read that LMDB has a larger 
performance advancement when dealing with many concurrent connections - 
so maybe that's what I was missing?

Anyway - so now I'm going to do more extensive performance testing with 
1.3.0.rc1, comparing LMDB and Berkley and Sqlite3 - comparing those 
three to each other.

Are there any instructions or suggestion for how to switch between these 
three? Can I just re-run the "configure": and "make" commands? Or do I 
need to uninstall first? Or something else?

And do I need to unload LMDB somehow first each time I switch away from 
LMDB? Or does it just go away after deleting the underlying files?

Any suggestions?

Thanks!!

Rob McEwen, invaluement