Fix issue

There were two problems, firstly `==` was used which always resulted in false as a property on the object was a pointer.  Secondly related, but not mutated, objects were not included in the validation set making them appear to be deleted.

internal/db/definition_validation.go

@@ -818,7 +818,9 @@ func validateFieldNotMutated(
 
 		for _, newField := range newSchema.Fields {
 			oldField, exists := oldFieldsByName[newField.Name]
-			if exists && oldField != newField {
+
+			// DeepEqual is temporary, as this validation is temporary
+			if exists && !reflect.DeepEqual(oldField, newField) {
 				return NewErrCannotMutateField(newField.Name)
 			}
 		}

internal/db/schema.go

@@ -376,11 +376,6 @@ func (db *db) updateSchema(
 		return err
 	}
 
-	oldDefs := make([]client.CollectionDefinition, 0, len(allExistingCols))
-	for _, col := range allExistingCols {
-		oldDefs = append(oldDefs, col.Definition())
-	}
-
 	for _, schema := range proposedDescriptionsByName {
 		previousSchema := existingSchemaByName[schema.Name]
 
@@ -498,7 +493,25 @@ func (db *db) updateSchema(
 			return err
 		}
 
-		err = db.validateSchemaUpdate(ctx, oldDefs, definitions)
+		oldDefs := make([]client.CollectionDefinition, 0, len(allExistingCols))
+		for _, col := range allExistingCols {
+			oldDefs = append(oldDefs, col.Definition())
+		}
+
+		defNames := make(map[string]struct{}, len(definitions))
+		for _, def := range definitions {
+			defNames[def.GetName()] = struct{}{}
+		}
+
+		newDefs := make([]client.CollectionDefinition, 0, len(definitions))
+		newDefs = append(newDefs, definitions...)
+		for _, existing := range allExistingCols {
+			if _, ok := defNames[existing.Definition().GetName()]; !ok {
+				newDefs = append(newDefs, existing.Definition())
+			}
+		}
+
+		err = db.validateSchemaUpdate(ctx, oldDefs, newDefs)
 		if err != nil {
 			return err
 		}

tests/integration/schema/updates/add/field/with_relation_test.go

@@ -16,6 +16,7 @@ import (
 	testUtils "github.com/sourcenetwork/defradb/tests/integration"
 )
 
+// This test ensures that nearby relation fields are not failing validation during a schema patch.
 func TestSchemaUpdatesAddField_DoesNotAffectExistingRelation(t *testing.T) {
 	test := testUtils.TestCase{
 		Actions: []any{
@@ -38,7 +39,6 @@ func TestSchemaUpdatesAddField_DoesNotAffectExistingRelation(t *testing.T) {
 						{ "op": "add", "path": "/Book/Fields/-", "value": {"Name": "rating", "Kind": 4} }
 					]
 				`,
-				ExpectedError: "mutating an existing field is not supported.",
 			},
 		},
 	}