Phoenix 180

First revision for review.  There are some open points here.  Still no test case added to consume the stats.  Will do the performance test once the system is available with me.
I think all this periodic checking of stats table itself wont't be needed is what you mean? So my doubt is this suppose I have some select queries coming periodically to a table and there are updations also happening to that table, if we are able to collect the stats periodically, for the newer select queries we would be able to use the udpated information right? Only if we collect the stats during re-load it would mean that if there is no schema change or index addition/deletion the updated stats info may not be used. For me I think periodic updation of the stats would be a better choice.