Disk-storage support functions

To provide the ability to perform special processing on the internal representation of an opaque type that it is stored on disk, you can define the following disk-storage support functions for an opaque type.

assign()

Special processing required just before a row that contains the opaque-type column is inserted into the table (written to disk)

destroy()

Special processing required just before a row that contains the opaque-type column is deleted from a table (removed from disk)

The disk internal representation is the contents of the C structure that is actually written to disk for the opaque-type column. The assign() and destroy() support functions are useful for opaque types that contain smart large objects. For such data types, assign() and destroy() can provide management of the associated smart large object as well as any necessary modification of the internal representation.