Fix retrieval of facets with cascade

[ashish-goswami]

Fixes #4310
Currently we are not able to fetch fecets associated with scalar predicate when using
cascade directive.
While processing cascade directive, we update uidMatrix. Every uid in uidMatrix is checked if
it is present in destUIDs, if not we remove it from uidMatrix. We also remove entry from
facetsMatrix for same uid. This works fine when predicate is of uid/[uid] type.
When predicate is of scalar type, destUIDs and uidMatrix will be empty, hence we should not
update facetsMatrix as facets here are corresponding to valueMatrix.
This PR avoid updating facetsMatrix when a uid list in uidMatrix is empty in updateUidMatrix.

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This change is 

[pawanrawal]

Reviewed 2 of 2 files at r1.
Reviewable status: all files reviewed, 3 unresolved discussions (waiting on @ashish-goswami)

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query/query_facets_test.go, line 1134 at r1 (raw file):

}

func TestFacetsCascadeScalarPredicate(t *testing.T) {

Add another case where cascade removes one of the results. Facets should be retrieved for the other uid.

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query/query_facets_test.go, line 1176 at r1 (raw file):

	js := processQueryNoErr(t, query)
	fmt.Println(js)

remove

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query/query_facets_test.go, line 1225 at r1 (raw file):

	populateClusterWithFacets()
	query := `{
		q(func: uid(1, 23)) @cascade {

Can remove top level cascade or add another case where cascade is only applied on child.

[ashish-goswami]

Reviewable status: 0 of 2 files reviewed, 3 unresolved discussions (waiting on @pawanrawal)

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query/query_facets_test.go, line 1134 at r1 (raw file):

Previously, pawanrawal (Pawan Rawal) wrote…

Add another case where cascade removes one of the results. Facets should be retrieved for the other uid.

updated TestFacetsCascadeUIDPredicate to have uid 24 also. This uid has name, but doesn't have friend, hence it should not be retrieved.

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query/query_facets_test.go, line 1176 at r1 (raw file):

Previously, pawanrawal (Pawan Rawal) wrote…

remove

Done.

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query/query_facets_test.go, line 1225 at r1 (raw file):

Previously, pawanrawal (Pawan Rawal) wrote…

Can remove top level cascade or add another case where cascade is only applied on child.

Removed top level cascade.

[pawanrawal]

Reviewed 2 of 2 files at r2.
Reviewable status: complete! all files reviewed, all discussions resolved

[manishrjain]

Reviewed 2 of 2 files at r2.
Reviewable status: complete! all files reviewed, all discussions resolved