Performance of a Joined View

Maptitude displays and accesses data in a joined view using indices for the fields on which the join is based. It utilizes any appropriate permanent index when available, and constructs a temporary index in all other cases. In general, you obtain the best performance by creating a permanent index for any field that is used in a joined view. However, for views with a small number of records (e.g., 2500 or less), the difference in performance may be insignificant.

If you have specific knowledge about the relationship between records in the left and right views, you can specify one of several options that increase the speed of working with joined views. For example, if you know that the right view contains exactly one record for each record in the left view, Maptitude can use this information to make data access and update more efficient.

In general, the more complex the joined view, the more overhead there is in navigating through the view (e.g., looping over records). If you need to perform extensive navigation on a joined view, consider using ExportView() to save the results of a join as a new physical table. This is appropriate when data in the component views change relatively infrequently, or when the performance on a multiple-table joined view is inadequate for a particular application.