[Rails] database performance in AR unit tests

[yerejm]

> It doesn't help much; SQLite3 remains ~4x slower than SQLite2.  Can
> anyone corroborate these results on another platform?

Nope. There's a SQLite3 slowness, but not a ~4x slowness.

FBSD 5.3, P2-400
~66  SQLite 2.8.15 with 2.2.3 C bindings
~69  MySQL 4.1.10 with 2.5.1 C bindings
~70  MySQL 4.1.10 with included Ruby bindings
~107  PostgreSQL 8.0.1 with 0.7.1 C bindings
~71  SQLite 3.0.8 with 1.1.0 C bindings