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MVGs configured without Primary ID fields require separate queries to display each parent record and each set of child records. For example, for a list applet that displays 10 records and two MVGs per record, a total of 21 queries would be required to populate the applet: one query to populate the parent records and 20 additional queries (two per parent record) to populate the MVGs. The number of queries executed is many times the number actually required.
You can avoid unnecessary queries by configuring a Primary ID field on the master business component. The Primary ID field serves as a foreign key from a parent record to one primary child record in the detail business component. This allows the application to perform a single query using a SQL join to display values for the parent record and the primary child record in the applet. In other words, it defers having to perform additional queries for the MVG until the user opens the MVG and displays a list of all child records.
List applets receive the most performance benefit from using Primary ID fields because list applets typically access a large number of records and each record may have one or more MVGs associated with it. The Primary ID field avoids having to submit queries for each MVG for every parent record.
Form applets can also benefit from Primary ID fields, even though in form applets only one parent record is accessed at a time. A Primary ID field allows the application to submit a single query for each new parent record displayed, rather than having to perform multiple queries for every MVG on the form applet. This can improve performance as the user moves from one record to another.
|Performance Tuning Guide|