APPLY operator

The APPLY operator creates an action that applies changes to the database.

Syntax

APPLY [nestedBlock] [SERIALIZABLE] [action]

where nestedBlock has one of two possible syntaxes:

NESTED LOCAL
NESTED (propertyId1, ..., propertyIdN)

Description

The APPLY operator creates an action that applies changes to the database. By specifying the keyword NESTED you can specify local properties whose changes are not dropped when applying the changes. This operator also includes an action to be executed before applying the changes to the database.

Parameters

• LOCAL

  Keyword. If specified, all local properties preserve their changes after the APPLY operator is executed.

• propertyId1, ..., propertyIdN

  List of local properties. Each list element is a property ID. The local properties specified in the list will preserve their changes after the operator is executed.

• SERIALIZABLE

  A keyword that sets the transaction isolation level to "Serializable".

• action

  A context-dependent operator that describes an action to be executed before applying changes. It is executed in the same transaction as the application of changes.

Examples

CLASS Sku;
id = DATA INTEGER (Sku);

in = DATA LOCAL BOOLEAN (Sku);
applyIn()  {
    in(Sku s) <- TRUE WHERE id(s) == 123;
    APPLY NESTED (in[Sku]) {};
    IF canceled() THEN
        MESSAGE applyMessage();
    FOR in(Sku s) DO
        MESSAGE id(s); // shows '123'
}

calculateInTransaction()  {
    APPLY {
        id(Sku s) <- (GROUP MAX id(Sku ss)) (+) 1; // putting down a new code inside the transaction
    }
}