[Maria-developers] Getting the columns from LEX or THD

Hi all, I wanted to retrieve a tables columns i.e its schema definition when a query is executed. I figured out LEX and THD structures store these in different variables for different queries. I wanted to get the same when a simple INSERT query is executed, e.g INSERT INTO <table> VALUES(<values>). Where can I find it? Is there any mechanism to get a tables schema that will work for any kind of query? Thanks, Sriram