Chapter 10 Achieving Optimum Performance with PowerDynamo

Expensive methods and properties

DynaScript consists of several objects made up of methods and properties. In general, methods or properties that cause a connection to a database to be created or a document to be loaded are expensive to execute. When possible, you should avoid excessive use of the more expensive methods and properties in Web sites that hold performance at a premium.

For example, suppose you wanted to display the URL of the parent of your current document. Using the parent property is an expensive way of doing this.

<!--SCRIPT
    document.WriteLn( document.parent.location );
-->

document.parent may require that the parent document be loaded from the database or file system. This may in turn, bump a document out of the document cache if the cache is full. A more resourceful way of obtaining the same information is to use document.location with the substring method to extract the parent's URL from the current URL. This is less expensive since the current document is already loaded.

<!--script
    index=document.location.lastIndexOf("/");
    document.writeln( document.location.substring( 0,index ) );
-->

The more expensive DynaScript methods and properties include:

connection.simulateCursors with databases (such as Adaptive Server Enterprise) that do not support backward movement through result sets.
query.GetRowCount with databases (such as Adaptive Server Enterprise) that do not support row counts.
new Connection constructor this kind of connection does not make use of the connection pool.