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Related Foundsets

Foundsets are often constrained or filtered by a Relation. In this situation, the foundset is said to be a Related Foundset and its default SQL query will include in its Where Clause, the parameters by which to constrain the foundset.

It is important to make the distinction that a relation and a foundset are not one in the same. Rather, a relation name is used to reference a specific foundset object within a given context. The context for a related foundset is always a specific record object. But for convenience, related foundsets may be referenced within a form's scripting scope and as a property of any foundset. However in these cases, the context is always implied to be the selected record in the context.

For example:

Take a predefined Relation, customers_to_orders, which models a one-to-many relationship between a customers table and an orders table. The following three lines of code, executed within the scripting scope of a form based on the customers table, all produce the same result.

// Returns the number of orders for the selected customer record in this form's foundset
customers_to_orders.getSize();

// ...the same as:
foundset.customers_to_orders.getSize();

// ...also the same as:
foundset.getSelectedRecord().customers_to_orders.getSize();

Related foundsets can be chained together using relation names. Again, the shorthand implies the context of the selected record for each foundset.

For Example:

// Returns the number of order details for the selected order record of the selected customer:
customers_to_orders.orders_to_order_details.getSize();

// ...is the same as:
customers_to_orders.getSelectedRecord().orders_to_order_details.getSelectedRecord().getSize();

Foundsets and Data Broadcasting

A Foundset may be automatically updated when the client receives a Data Broadcast Event . If the data change affected the table to which the foundset is bound, the foundset will be refreshed to reflect the change.

Performing Batch Updates

Foundsets are typically updated on a record-by-record basis, either as the user operates on a foundset-bound GUI component, or through programmatic interactions. However, sometimes it is necessary to perform an update to an entire foundset. For performance reasons, it is not advised that this be done by programmatically iterating over the foundset's records. Rather, it is recommended that batch updates be performed using the JSFoundsetUpdater API.

The Foundset Updater API is ideal to use for the following situations:

Updating an entire foundset

This essentially has the effect of issuing a SQL UPDATE statement using the WHERE clause that constrains the foundset. This presents a significant performance advantage over updating records individually. In the example below, a related foundset is updated, meaning all orders belonging to the selected customer will be affected.

var fsUpdater = databaseManager.getFoundSetUpdater(customers_to_orders);
fsUpdater.setColumn('status',101);
fsUpdater.performUpdate();

Updating a partial foundset with different values for each record

The Foundset Updater API can also be used to update part of a foundset. Moreover, unlike the above example, this approach allows for different values for each record. In the example below, the first 4 records (starting from the selected index) are updated by specifying an array of values for each column that is affected.

//	update first four records
var fsUpdater = databaseManager.getFoundSetUpdater(foundset);
fsUpdater.setColumn('customer_type',[1,2,3,4]);
fsUpdater.setColumn('my_flag',new [1,0,1,0]);
fsUpdater.performUpdate();

Updating each record individually

The Foundset Updater API can also be used to update records individually, but still holds a performance advantage over iterating on a foundset, which has more overhead and can cause the foundset's cache size to increase unnecessarily. In the example below, each record in the foundset is updated with a unique value (A simple counter is incremented, which is arbitrary, but demonstrates that each record can be updated with a unique value.)

var count = 0;
var fsUpdater = databaseManager.getFoundSetUpdater(foundset)
while(fsUpdater.next())
{
	fsUpdater.setColumn('degrees',count++);
}