Eliminate left joins with option value / group, state, country, county tables in search queries

On large data sets and/or export queries where we export a large set of contacts, we use a fair number of left joins. Basically we retrieve:

gender
prefix
suffix
state
country
world region

via a left join to the above tables. The above tables are pseudo-constants and are cached in either memcache or mysql query cache. So if we just retrieve the ids, we can then use an array lookup to retrieve the value.

On tests against a sample NYSS db and the EFF db, we've seen a 8-12x query improvement on the entire contact set.