Hello. Describe the changes here, and why they are needed.
Refactored SQL Column and Table structures to use space_def instead of native fields. All temporal memory is allocated on region to prevent memory leaks and easely manage memory with frequent insertions on SQL expression parsing. Introduced space_def pointer in Expr instead of Table pointer. The ResolveSelfReference function requires Table pointer to refer to, but it doesn't exist in our scenarios yet. With correctly-initialized consistent space_def structure this would no problem. This preliminary tasks should make able to move SQL Checks in Server code.