Using Caché Objects - InterSystems Documentation

Caché ObjectScript. These queries are processed using the same %Library.ResultSet interface
as queries written in SQL but are defined differently.
To define a Caché ObjectScript query, specify %Query for the query type and provide necessary
information for the related parameters (ROWSPEC and CONTAINID). For example, if a
Book class has Author and Title properties, you could define an All query (to list all books)
as follows:
Query All() As %Query(CONTAINID = 1, ROWSPEC = "Title:%String,Author:%String")
{
}
The actual query definition contains no other information, as the query processing code is
defined in three class methods that are associated with it. These methods are:
• querynameExecute — This method invokes the query. For queries that use the SELECT
command, this method also prepares the query for subsequent traversal and data retrieval.
• querynameFetch — Calling this method returns a row of the result set; each subsequent
call returns the next row.
• querynameClose — This method performs cleanup operations.
where queryname is the name of the query.
In addition, Caché automatically generates querynameGetInfo and querynameFetchRows
methods from the row specification and querynameFetch method respectively. Your application
does not call any of these methods directly — the %Library.ResultSet object uses them
to process query requests.
8.2.1 The querynameExecute Method
The querynameExecute method provides all of the setup needed to retrieve data. For queries
using SQL code, this typically includes declaring and opening a cursor. The
querynameExecute method returns status information and uses a %Binary variable passed
by reference as its first argument. This argument passes information between the query
methods and contains all information needed by the various query methods.
For example, if a query called ByName has no runtime parameters, the ByNameExecute
method has the following signature:
ClassMethod ByNameExecute(ByRef qHandle As %Binary) As %Status {
// query setup code here
Quit $$$OK
}
User-Written Class Queries
Using Caché Objects 59