This is the factory interface of the XPLAINFactory facility. It extends the
possibilities and provides a convenient protocol to explain queries
on basis of the query execution plan. This plan manfifests in Derby in the
different ResultSets and their associated statistics. The introduction of
this factory interface makes it possible to switch to another implementation
or to easily extend the API.
This method returns an appropriate visitor to traverse the
ResultSetStatistics. Depending on the current configuration,
the perfect visitor will be chosen, created and cached by this factory
method.
Returns:
a XPLAINVisitor to traverse the ResultSetStatistics
This method gets called when the user switches off the explain facility.
The factory destroys for example the cached visitor implementation(s) or
releases resources to save memory.