Database Reference
In-Depth Information
Figure 5. Fuzzy Query Tree
Executor
module's physical access mechanisms:
sequential scan
, if
ndex scan
and
bitmap heap scan
were extended as follows: if the node has a fuzzy predicate then it computes the membership degree of
each row taking into account the node's fuzzy predicate attached to the list
FuzzyPred
, and it is pro-
jected in the
Gr_memb
attribute attached to the
Target Entry List
(
tlist
), thus is generated
fuzzy rows
.
Also
nested loop
,
hash
and
merge
physical join operators were extended, so once they receive a fuzzy
row then propagate the membership degree bottom-up for the next operator through the attribute
Gr
_
memb
.
Additional tasks are carried out if we find a fuzzy subquery at FROM clause, we identify this in
the
rtable
structure and process the fuzzy subquery. Furthermore, the Executor module computes the
membership degree according to the fuzzy term (predicate, comparator, quantifier, connector, modifier
or partition)
Finally if we find Fuzzy Set operations, we determined the type of these operations (INTERSECT,
UNION or EXCEPT) in order to apply the Fuzzy Set operation (classical operation extended).
