ATG Repository Guide

You can create a repository filter using the <rql-filter> tag in the definition file for an item descriptor. The <rql-filter> tag encloses a Repository Query Language 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 &lt; ?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 second 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.CurrentDate is used as a parameter (as in this example), the filtering logic will call getTimeAsTimeStamp() on that object and use that as the value of the parameter. This allows you to have a CurrentDate service 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 &lt. For information about using RQL, see the Repository Query Language section in the Repository Queries chapter.