You can create a repository filter with the <rql-filter> tag in the definition file for an item descriptor. The <rql-filter> tag encloses an RQL statement, as in the following example:
<item-descriptor name="article"> <rql-filter> <rql>name starts with "n"</rql> </rql-filter> <table name="article" id-column-names="article_id"> <property name="name"/> <property name="date"/> </table> </item-descriptor>
This setting causes queries and item lookups for this item descriptor to return only items whose name property starts with n. The SQL repository issues SQL in the form of an extra WHERE clause condition to implement filtering so any given query or item lookup should be no slower with a reasonable filter tacked on.
You can also use RQL substitution parameters in your filter query. For example:
<item-descriptor name="article"> <rql-filter> <rql>name starts with ?0 or availabilityDate < ?1</rql> <param value="n"></param> <param bean="/myApp.IssueDate"></param> </rql-filter> <table name="article" id-column-names="article_id"> <property name="name"/> <property name="availabilityDate" data-type="timestamp"/> </table> </item-descriptor>
In this example, the RQL parameters are substituted into the query:
The first parameter is a simple constant value. Typically it is not necessarily to substitute constant values as they can be inlined in the RQL query string.
The second parameter is a Nucleus component. If an object of type
atg.service.util.CurrentDateis used as a parameter (as in this example), the filtering logic callsgetTimeAsTimeStamp()on that object and uses that as the value of the parameter. This lets you have aCurrentDateservice used in a filter. Also note, as in this example, that the “less than” symbol (<) is a markup character and must be escaped in your XML file as<.
For information about RQL, see the Repository Query Language section in the Repository Queries chapter.
