- bdb_get(+DB, ?Key, -Value) is nondet
- Query the database. If the database allows for duplicates this
predicate is non-deterministic, otherwise it is semidet. Note
that if Key is a term this matches stored keys that are
variants of Key, not unification. See =@=/2. Thus, after
bdb_put(DB, f(X), 42), we get the following query results:
bdb_get(DB, f(Y), V) binds Value to
42, while Y is left
bdb_get(DB, f(a), V) fails.
bdb_enum(DB, f(a), V) succeeds, but does not perform any
indexing, i.e., it enumerates all key-value pairs and
performs the unification.