Multiple Column ORDER BYs now supported

[Jak Sprats]

Hi All,

I added Multiple Column ORDER BYs to AlchemyDB, so the following
queries are possible:
SELECT * FROM obycol WHERE "id BETWEEN 1 AND 10 ORDER BY i,j ASC,k,l
DESC,m"
SELECT * FROM obycol WHERE "id IN (1,2,3,4,5,6) ORDER BY k, m DESC
LIMIT 4 OFFSET 3"

I did some performance tests:
https://gist.github.com/774345

Conclusions:
multiple column sorting has almost no overhead as compared to single
column sorting, but sorting has a 25% hit as compared to index
iteration.

This is a commonly used SQL feature and many apps can not properly
list SELECT results w/o this feature.

- Jak

p.s. Multiple Column Indexes are next, after that, AlchemyDB will be
TPCC-able and even optimisable and will perform VERY well @ TPCC-like
apps