Method updateVars

query/query.go:1535–1547

updateVars is used to update the doneVars map with the value of the variable from the SubGraph. The variable could be a uid or a value variable. It is called twice 1. To populate sg.Params.ParentVars map with the value of a variable to pass down to children subgraphs in a query. 2. To populate req.V

(doneVars map[string]varValue, sgPath []*SubGraph)

// subgraphs in a query.
// 2. To populate req.Vars, which is used by other queries requiring variables..
func (sg *SubGraph) updateVars(doneVars map[string]varValue, sgPath []*SubGraph) error {
	// NOTE: although we initialize doneVars (req.Vars) in ProcessQuery, this nil check is for
	// non-root lookups that happen to other nodes. Don't use len(doneVars) == 0 !
	if doneVars == nil || (sg.Params.Var == "" && sg.Params.FacetVar == nil) {
		return nil
	}

	sgPathCopy := append(sgPath[:0:0], sgPath...)
	if err := sg.populateUidValVar(doneVars, sgPathCopy); err != nil {
		return err
	}
	return sg.populateFacetVars(doneVars, sgPathCopy)
}

// populateUidValVar populates the value of the variable into doneVars.
func (sg *SubGraph) populateUidValVar(doneVars map[string]varValue, sgPath []*SubGraph) error {