Is there a way to view input relations?

[doug-galvanick]

In the subnet example in the tutorial, the output relation has two UUIDs. Is there a way to back reference those UUIDs to get the input relations they're associated with? Or would that be handled by an external program? Looking for something like dump Host where ....

Thanks!

// Type aliases
typedef UUID    = bit<128>
typedef IP4     = bit<32>
typedef NetMask = bit<32>

//IP host specified by its name and address.
input relation Host(id: UUID, name: string, ip: IP4)

//IP subnet specified by its IP prefix and mask
input relation Subnet(id: UUID, prefix: IP4, mask: NetMask)

// HostInSubnet relation maps hosts to known subnets
output relation HostInSubnet(host: UUID, subnet: UUID)

HostInSubnet(host_id, subnet_id) :- Host(host_id, _, host_ip),
                                    Subnet(subnet_id, subnet_prefix, subnet_mask),
                                    ((host_ip & subnet_mask) == subnet_prefix). // filter condition

[doug-galvanick]

It looks like the answer to this is to use indexes in conjunction with the query_index command.

https://github.com/vmware/differential-datalog/blob/master/doc/tutorial/tutorial.md#indexes

https://github.com/vmware/differential-datalog/blob/master/doc/command_reference/command_reference.md

[ryzhyk]

That's right. This is not as general as querying with an arbitrary where clause, but is the closest thing we have to that.

[doug-galvanick]

Thanks!