Critique of Data Model V.1

• Union Types

• Access Method Interface

• Functions

• Big Objects

• Arrays

Notes:

• Union types make the optimizer more complex:
  

• multiple query plans, indexes

• support only through abstract data types

• forces users to do-very difficult

• support through POSTQUEL functions

• No reasonable type for Union result-no variant type

• Used in V1 with an ANY type

• full support

• Done on later versions.

• Access Methods-Very Hard!!

• Understand locking

• How to interface to the buffer manager and be able to put, get, pin, and unpin pages.

• Understand the “state” of execution and data structures involved.

• 13 non-trivial routines

• Functions- path expressions can not be optimized, POSTQUEL easier to do, data protection, trusted-fast, untrusted-slow separate memory space