Support pointer in distinct query (#4471)

* Support pointer in distinct query

* extract transform pointer string

src/Adapters/Storage/Mongo/MongoStorageAdapter.js

@@ -10,6 +10,7 @@ import {
   transformKey,
   transformWhere,
   transformUpdate,
+  transformPointerString,
 } from './MongoTransform';
 import Parse                 from 'parse/node';
 import _                     from 'lodash';
@@ -483,9 +484,19 @@ export class MongoStorageAdapter {
 
   distinct(className, schema, query, fieldName) {
     schema = convertParseSchemaToMongoSchema(schema);
+    const isPointerField = schema.fields[fieldName] && schema.fields[fieldName].type === 'Pointer';
+    if (isPointerField) {
+      fieldName = `_p_${fieldName}`
+    }
     return this._adaptiveCollection(className)
       .then(collection => collection.distinct(fieldName, transformWhere(className, query, schema)))
-      .then(objects => objects.map(object => mongoObjectToParseObject(className, object, schema)));
+      .then(objects => objects.map(object => {
+        if (isPointerField) {
+          const field = fieldName.substring(3);
+          return transformPointerString(schema, field, object);
+        }
+        return mongoObjectToParseObject(className, object, schema);
+      }));
   }
 
   aggregate(className, schema, pipeline, readPreference) {

src/Adapters/Storage/Mongo/MongoTransform.js

@@ -1014,6 +1014,18 @@ const nestedMongoObjectToNestedParseObject = mongoObject => {
   }
 }
 
+const transformPointerString = (schema, field, pointerString) => {
+  const objData = pointerString.split('$');
+  if (objData[0] !== schema.fields[field].targetClass) {
+    throw 'pointer to incorrect className';
+  }
+  return {
+    __type: 'Pointer',
+    className: objData[0],
+    objectId: objData[1]
+  };
+}
+
 // Converts from a mongo-format object to a REST-format object.
 // Does not strip out anything based on a lack of authentication.
 const mongoObjectToParseObject = (className, mongoObject, schema) => {
@@ -1126,15 +1138,7 @@ const mongoObjectToParseObject = (className, mongoObject, schema) => {
           if (mongoObject[key] === null) {
             break;
           }
-          var objData = mongoObject[key].split('$');
-          if (objData[0] !== schema.fields[newKey].targetClass) {
-            throw 'pointer to incorrect className';
-          }
-          restObject[newKey] = {
-            __type: 'Pointer',
-            className: objData[0],
-            objectId: objData[1]
-          };
+          restObject[newKey] = transformPointerString(schema, newKey, mongoObject[key]);
           break;
         } else if (key[0] == '_' && key != '__type') {
           throw ('bad key in untransform: ' + key);
@@ -1345,4 +1349,5 @@ module.exports = {
   mongoObjectToParseObject,
   relativeTimeToDate,
   transformConstraint,
+  transformPointerString,
 };