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To support collections, the data store must subclass the following classes.
Class precedence list:
persistent-collection, persistent, standard-object, t
Abstract superclass of all collection types.
Class precedence list:
btree, persistent-collection, persistent, standard-object, t
A hash-table like interface to a BTree, which stores things in a semi-ordered fashion.
Class precedence list:
btree-index, btree, persistent-collection, persistent-object, persistent, standard-object, t
Secondary index to an indexed-btree.
Class precedence list:
indexed-btree, btree, persistent-collection, persistent, standard-object, t
A BTree which supports secondary indices.
To create the data store-appropriate type of btree, the data store implements this method (and possibly related methods) aginst their store-controller.
Construct a btree of the appropriate type corresponding to this store-controller.
Most of the user-visible operations over BTrees must be implemented.
Class indexing functions such as map-class
and
get-instances-by-value
and related functions are all
implemented using map-btree and map-index.
(setf get-value)
)
Mapping over the indices of a btree is important to derived facilities such as class indexing and the query subsystem.