Using Caché Objects - InterSystems Documentation

mation. Again, this method deletes all the instances of the specified class, as well as all
instances of its subclasses.
For example, to delete all Person objects (including all instances of subclasses of Person)
use the following code:
Do ##class(Person).%DeleteExtent()
The %DeleteExtent method will execute any %OnDelete callback methods, if present, for
each object it deletes.
You can also delete all instances of a class and its subclasses using the faster, but dangerous,
%KillExtent method:
Do ##class(Classname).%KillExtent()
Executing Queries
The %KillExtent method immediate kills all data associated with a class extent; no callbacks
are executed and no referential actions are performed. You should only use the %KillExtent
method on developmental systems on which you have no real data.
10.7 Executing Queries
Caché provides %ResultSet objects for executing queries and processing the results.
This involves several steps:
1. Preparing the query
2. Executing the query
3. Processing the query results
4. Closing the query
10.7.1 Query Metadata Methods
To use a query, associate it with a %ResultSet object and you can then manipulate in a number
of ways. The methods available for these operations are:
• ContainsId checks if the query returns object ID values. It returns an integer value
specifying the column number of the ID, if there is one; otherwise, it returns 0.
• GetParamCount returns an integer specifying the number of arguments that the query
takes.
Using Caché Objects 83