fix: Avoid populating order.ordering with empties. (#618)

- Resolves: #589 

- Description: Hunch mentioned in last week's meeting was correct, it was indeed a `make` where it would populate the array with empties and then append being called on top of it. Also removed the function `IsEmpty()`, we used to check for empty elements previously which was introduced in #481.

query/graphql/mapper/mapper.go

@@ -798,27 +798,27 @@ func toOrderBy(source *parserTypes.OrderBy, mapping *core.DocumentMapping) *Orde
 	}
 
 	conditions := make([]OrderCondition, len(source.Conditions))
-	for _, condition := range source.Conditions {
+	for conditionIndex, condition := range source.Conditions {
 		fields := strings.Split(condition.Field, ".")
 		fieldIndexes := make([]int, len(fields))
 		currentMapping := mapping
-		for i, field := range fields {
+		for fieldIndex, field := range fields {
 			// If there are multiple properties of the same name we can just take the first as
 			// we have no other reasonable way of identifying which property they mean if multiple
 			// consumer specified requestables are available.  Aggregate dependencies should not
 			// impact this as they are added after selects.
-			fieldIndex := currentMapping.FirstIndexOfName(field)
-			fieldIndexes[i] = fieldIndex
-			if i != len(fields)-1 {
+			firstFieldIndex := currentMapping.FirstIndexOfName(field)
+			fieldIndexes[fieldIndex] = firstFieldIndex
+			if fieldIndex != len(fields)-1 {
 				// no need to do this for the last (and will panic)
-				currentMapping = &currentMapping.ChildMappings[fieldIndex]
+				currentMapping = &currentMapping.ChildMappings[firstFieldIndex]
 			}
 		}
 
-		conditions = append(conditions, OrderCondition{
+		conditions[conditionIndex] = OrderCondition{
 			FieldIndexes: fieldIndexes,
 			Direction:    SortDirection(condition.Direction),
-		})
+		}
 	}
 
 	return &OrderBy{

query/graphql/mapper/targetable.go

@@ -106,13 +106,6 @@ type OrderCondition struct {
 	Direction SortDirection
 }
 
-func (oc OrderCondition) IsEmpty() bool {
-	if oc.Direction == "" && len(oc.FieldIndexes) == 0 {
-		return true
-	}
-	return false
-}
-
 type OrderBy struct {
 	Conditions []OrderCondition
 }

query/graphql/planner/order.go

@@ -103,11 +103,6 @@ func (n *orderNode) Explain() (map[string]interface{}, error) {
 	orderings := []map[string]interface{}{}
 
 	for _, element := range n.ordering {
-		// Skip all empty elements.
-		if element.IsEmpty() {
-			continue
-		}
-
 		// Build the list containing the corresponding names of all the indexes.
 		fieldNames := []string{}
 		for _, fieldIndex := range element.FieldIndexes {

query/graphql/planner/select.go

@@ -417,7 +417,7 @@ func (p *Planner) Select(parsed *mapper.Select) (planNode, error) {
 		docMapper: docMapper{&parsed.DocumentMapping},
 	}
 	limit := parsed.Limit
-	order := parsed.OrderBy
+	orderBy := parsed.OrderBy
 	groupBy := parsed.GroupBy
 
 	aggregates, err := s.initSource()
@@ -435,7 +435,7 @@ func (p *Planner) Select(parsed *mapper.Select) (planNode, error) {
 		return nil, err
 	}
 
-	orderPlan, err := p.OrderBy(parsed, order)
+	orderPlan, err := p.OrderBy(parsed, orderBy)
 	if err != nil {
 		return nil, err
 	}