To CONSTRAINT or Not to CONSTRAINT

I've been having these long (good) drawn out conversations with a colleague of mine recently about constraints in a datawarehouse environment. Since I come from an OLTP environment, I want to put a constraint on everything. He on the other hand wants any constraints enforced through code.

I can understand that constraints my slow down table loads, but with the volume of data we are currently using (100 million row tables), I just don't see that as a huge impact on performance. For me, writing less code is better than any minimal performance gains we might achieve.

For instance, today he told me he wanted to add a new column. The possible values would either be M or G. I asked (I'm lead on the project) him to throw a CHECK constraint on the table limiting the values that can go in that field.

For me, I guess it's a support issue and part database purist issue. Use it for more than a bucket, Oracle's expensive. It forces developers to deal with that and will immediately tell them if they have done something wrong. It also makes support a tad easier as they won't have to wonder what actually goes in the field.

We talked at length about it but never really came to a decision (i.e. I couldn't convince him).

I know that a benchmark test would be the best way to prove either way, but I don't have the time right now to do it. Perhaps when things slow down again I will.

Any suggestions out there?