Google's an engineering company and I think they should fight back as such. Get together a team of your best and brightest, take Postgres, and turn it into a drop-in replacement for Oracle. And be very public about your efforts.
Because Oracle doesn't own any patents on the implementation of relational databases that they couldn't also sue Google over . . . The most engineer-ish thing to do is a back of the envelope calculation: 1. Estimate how much it'd cost to fight the suit. 2. Estimate the probability of winning. 3. Estimate the damages if you lose. 4. Estimate Oracle's ask for licensing the patents. If (1 + 2 * 3) < 4, fight, else settl…
So here is the cheap way for Google to attack Oracle: Fund startups that research how much it costs to switch from Oracle servers to Postgres, then sell reports to Oracle customers so they can get lower prices.
I can't see that funding some startups makes you vulnerable to suits, but I am not a lawyer.