Add other filters to expand()

[MichelDiz]

Experience Report

reference: https://discuss.dgraph.io/t/how-to-find-relationship-between-two-nodes/7495/3?u=micheldiz

What you wanted to do

Use expand func to reduce hard typing. This increases the users experience.

{
	M as var(func: type(Person)) @filter(eq(name, 'Martin Sheen')
	O as var(func: type(Person)) @filter(eq(name, 'Oliver Stone')

	q(func: uid(O) @recurse(depth: 50, loop: true) {
		expand(User) @filter(uid(M))
	}
}

What you actually did

{
	M as var(func: type(Person)) @filter(eq(name, 'Martin Sheen')
	O as var(func: type(Person)) @filter(eq(name, 'Oliver Stone')

	q(func: uid(O) @recurse(depth: 50, loop: true) {
		friend @filter(uid(M))
		~friend @filter(uid(M))
		follows @filter(uid(M))
		~follows @filter(uid(M))
             # maybe even more edges to add (...)
	}
}

Why that wasn't great, with examples

The only problem is that you need to hard type all possible edges to accomplish that. Using "Expand(Type)" with a filter it would catch all possible edges from the Type Definition and apply the filter as a "template".

[rderbier]

Postman repro case https://cloudy-astronaut-679688.postman.co/workspace/e8602b95-3843-46e0-8f3b-2d994602fa7a/collection/24547389-2ebb8f27-7be7-4493-a152-dca9b4782b5b?action=share&creator=24547389

using predicate "in" with @reverse.
you can declare the predicate "~in" in a type.
expand(all) will work : it will follow all the relationships declared in the node type, so it will follow ~in if present.
in our case the ~in relationship goes to a node of type "N5803".
If we expand(all) @filter(type(N5803)) , the query does not follow the ~in relationship. See the postman test with other options working.

[MichelDiz]

The link isn't working for me.

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But I don't get your point. Are you saying that expand function has filters? last time I checked the code it wasn't.

[dwilson1988]

https://dgraph.io/docs/query-language/expand-predicates/#filtering-during-expand expand supports type filters only, but they do not work on reverse predicates.

[rderbier]

my bad not reading this issue correctly.
We must open a separate issue... I'll do it.

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