Still, what if there are legitimate
2 letter searches, like for "Ur" as someone else pointed out?
The only way to make mysql index shorter words is by recompiling and
setting MIN_WORD_LEN to a different number. They claim that changing
this variable from the current value of 4 to 0 will enlarge the index
by a factor of 20. So maybe we should go with 2. After that, the
indexes have to be rebuilt.
Axel