[mamcx]

I'm doing a relational lang(http://tablam.org), that could be considered to be a in memory kind of db.

Is certainly challenging.

Just look at joins. You have (at least) 2 nested loop joins algos, then sorted and hash joins, and then you have cross and left, right, inner and outers. All of them with small subtle tricks to make it performant (in theory: You can build all on top of CROSS. But! That will be very wastefull very fast!)