feat: Add alias to groupBy related object (#1579)

Resolves #1578
Resolves #1551
Part-of: #1279

## Description
- Add some tests of existing object_id functionality.
- Add implementation for groupBy alias.
- Add tests for groupBy alias ability.
- Fix the previous panic using alias, with more user friendly error.
- Add tests for panic fix.
- Make a const for `_id`.
- Schema Test to ensure the field we want to alias exists (even though
it actually existed from before)

client/request/consts.go

@@ -15,6 +15,10 @@ const (
 	// https://spec.graphql.org/October2021/#sec-Type-Name-Introspection
 	TypeNameFieldName = "__typename"
 
+	// This is appended to the related object name to give us the field name
+	// that corresponds to the related object's join relation id, i.e. `Author_id`.
+	RelatedObjectID = "_id"
+
 	Cid         = "cid"
 	Data        = "data"
 	DocKey      = "dockey"

client/request/select.go

@@ -89,13 +89,17 @@ func (s *Select) validateGroupBy() []error {
 			}
 
 			var fieldExistsInGroupBy bool
+			var isAliasFieldInGroupBy bool
 			for _, groupByField := range s.GroupBy.Value().Fields {
 				if typedChildSelection.Name == groupByField {
 					fieldExistsInGroupBy = true
 					break
+				} else if typedChildSelection.Name == groupByField+RelatedObjectID {
+					isAliasFieldInGroupBy = true
+					break
 				}
 			}
-			if !fieldExistsInGroupBy {
+			if !fieldExistsInGroupBy && !isAliasFieldInGroupBy {
 				result = append(result, client.NewErrSelectOfNonGroupField(typedChildSelection.Name))
 			}
 		default:

db/collection_update.go

@@ -398,7 +398,9 @@ func (c *collection) isSecondaryIDField(fieldDesc client.FieldDescription) (clie
 		return client.FieldDescription{}, false
 	}
 
-	relationFieldDescription, valid := c.Description().GetField(strings.TrimSuffix(fieldDesc.Name, "_id"))
+	relationFieldDescription, valid := c.Description().GetField(
+		strings.TrimSuffix(fieldDesc.Name, request.RelatedObjectID),
+	)
 	return relationFieldDescription, valid && !relationFieldDescription.IsPrimaryRelation()
 }
 
@@ -431,7 +433,7 @@ func (c *collection) patchPrimaryDoc(
 	_, err = primaryCol.UpdateWithKey(
 		ctx,
 		primaryDockey,
-		fmt.Sprintf(`{"%s": "%s"}`, primaryField.Name+"_id", docKey),
+		fmt.Sprintf(`{"%s": "%s"}`, primaryField.Name+request.RelatedObjectID, docKey),
 	)
 	if err != nil {
 		return err

planner/mapper/errors.go

@@ -12,8 +12,16 @@ package mapper
 
 import "github.com/sourcenetwork/defradb/errors"
 
+const (
+	errInvalidFieldToGroupBy string = "invalid field value to groupBy"
+)
+
 var (
 	ErrUnableToIdAggregateChild = errors.New("unable to identify aggregate child")
 	ErrAggregateTargetMissing   = errors.New("aggregate must be provided with a property to aggregate")
 	ErrFailedToFindHostField    = errors.New("failed to find host field")
 )
+
+func NewErrInvalidFieldToGroupBy(field string) error {
+	return errors.New(errInvalidFieldToGroupBy, errors.NewKV("Field", field))
+}

planner/mapper/mapper.go

@@ -87,8 +87,31 @@ func toSelect(
 		return nil, err
 	}
 
-	// If there is a groupBy, and no inner group has been requested, we need to map the property here
+	// Resolve groupBy mappings i.e. alias remapping and handle missed inner group.
 	if selectRequest.GroupBy.HasValue() {
+		groupByFields := selectRequest.GroupBy.Value().Fields
+		// Remap all alias field names to use their internal field name mappings.
+		for index, groupByField := range groupByFields {
+			if _, fieldHasMapping := mapping.IndexesByName[groupByField]; fieldHasMapping {
+				// Not an alias as is already mapped.
+				continue
+			} else if _, isAlias := mapping.IndexesByName[groupByField+request.RelatedObjectID]; isAlias {
+				// Remap the alias to it's actual internal name.
+				groupByFields[index] = groupByField + request.RelatedObjectID
+			} else {
+				// Field is not mapped nor is an alias, then is invalid field to group on. This can be
+				// incase of when an alias might have been used on groupBy relation from the single side.
+				return nil, NewErrInvalidFieldToGroupBy(groupByField)
+			}
+		}
+
+		selectRequest.GroupBy = immutable.Some(
+			request.GroupBy{
+				Fields: groupByFields,
+			},
+		)
+
+		// If there is a groupBy, and no inner group has been requested, we need to map the property here
 		if _, isGroupFieldMapped := mapping.IndexesByName[request.GroupFieldName]; !isGroupFieldMapped {
 			index := mapping.GetNextIndex()
 			mapping.Add(index, request.GroupFieldName)

planner/type_join.go

@@ -356,7 +356,7 @@ func (n *typeJoinOne) Next() (bool, error) {
 
 func (n *typeJoinOne) valuesSecondary(doc core.Doc) core.Doc {
 	fkIndex := &mapper.PropertyIndex{
-		Index: n.subType.DocumentMap().FirstIndexOfName(n.subTypeFieldName + "_id"),
+		Index: n.subType.DocumentMap().FirstIndexOfName(n.subTypeFieldName + request.RelatedObjectID),
 	}
 	filter := map[connor.FilterKey]any{
 		fkIndex: doc.GetKey(),
@@ -386,7 +386,7 @@ func (n *typeJoinOne) valuesSecondary(doc core.Doc) core.Doc {
 
 func (n *typeJoinOne) valuesPrimary(doc core.Doc) core.Doc {
 	// get the subtype doc key
-	subDocKey := n.docMapper.documentMapping.FirstOfName(doc, n.subTypeName+"_id")
+	subDocKey := n.docMapper.documentMapping.FirstOfName(doc, n.subTypeName+request.RelatedObjectID)
 
 	subDocKeyStr, ok := subDocKey.(string)
 	if !ok {
@@ -546,7 +546,7 @@ func (n *typeJoinMany) Next() (bool, error) {
 		// @todo: handle index for one-to-many setup
 	} else {
 		fkIndex := &mapper.PropertyIndex{
-			Index: n.subSelect.FirstIndexOfName(n.rootName + "_id"),
+			Index: n.subSelect.FirstIndexOfName(n.rootName + request.RelatedObjectID),
 		}
 		filter := map[connor.FilterKey]any{
 			fkIndex: n.currentValue.GetKey(), // user_id: "bae-ALICE" |  user_id: "bae-CHARLIE"