Parameterized Queries

Instead of a main query, you can instead mark a function or variable declaration with an annotation that declares that function as the file's main query.

Variable Query Declarations

For example, before your main query may have been:

foreach device in network.devices
select { name : device.name }

Now you can instead write:

@query
deviceNames =
  foreach device in network.devices
  select { name: device.name };

This query can now be run in the same way as a main expression.

Parameterized Queries

Query declarations may also be given parameters. For example, we might have a function that finds all device interfaces that have too many subinterfaces:

findBadInterfaces(threshold) =
  foreach device in network.devices
  foreach iface in device.interfaces
  where length(iface.subinterfaces) > threshold
  select { name : device.name, ifaceName : iface.name };

We can expose this function as a query that can be run with two changes to the declaration:

@query
findBadInterfaces(threshold : Number) =
  foreach device in network.devices
  foreach iface in device.interfaces
  where length(iface.subinterfaces) > threshold
  select { name : device.name, ifaceName : iface.name };

• The first change is adding an @query annotation before the function's declaration.
• The second change is providing the type of the threshold parameter. Since threshold is a number, we declare threshold to have the type Number.

Note

• All query parameters must have a type annotation. For more information, see Parameter Type Annotations.

Note

• Return type annotations are also allowed on @query declarations, but are optional. For more information, see Return Type Annotations.