fromLocalDatastore doesn't work for Relations

[evgen-povt]

There was the same bug in iOS SDK - https://developers.facebook.com/bugs/938451159512610/

ParseQuery<ParseObject> queryState = ParseQuery.getQuery("State");
queryState.fromLocalDatastore();

try {
    ParseObject stateObject = queryState.get(stateId);
    List<ParseObject> parseObjectList = stateObject.getRelation("tests").getQuery().fromLocalDatastore().find();

    // parseObjectList is empty here. Although the data were fetched and pinned earlier.
    // it works perfect if remove fromLocalDatastore() in previous line
} catch (ParseException e) {
    Loggi.e(TAG, "ParseException: " + e);
}

[wangmengyan95]

Hi @evgen-povt, in order to use stateObject.getRelation("tests").getQuery().fromLocalDatastore(), when you pin a State class, you have to fetch the objects under tests relation and pin them explicitly.
For example:

ParseQuery<ParseObject> query = ParseQuery.getQuery("State");
List<ParseObject> objects = query.find();
for (ParseObject object : objects) {
  // Pin all children explicitly
  ParseObject.pinAll(object.getRelation("tests").getQuery().find());
  object.pin();
}

It is a little bit inconvenience and we will definitely improve it in the future.

[evgen-povt]

Hi @wangmengyan95,
thank you for the answer. It works!

I believe the issue shouldn't be marked as a question, but the bug, because the iOS SDK works as expected, and doesn't require to pin every relation explicitly.

[wangmengyan95]

@evgen-povt thanks for the information.

[Toofoo]

For a query from a ParseRelation , even if I call ParseObject.pinAllInBackground( ) when the Object is retrieved from the remote DB, I cannot find it in the LocalDataStore on a next call.
Are you sure that the pinAllInBackground() method works correctly for objects found from a ParseRelation?

[Toofoo]

I confirm that the query result is not persisted in cache even like this :
ParseObject.pinAll( myObject.getRelation("testRelation").getQuery().find() );
myObject.pin();

If then I call the same query from the localDatastore it will find the result only if I don't stop the application. If I restart the application the query from localDatastore will return an empty result.

[Allsimon]

Used to have the same issue... Honestly, triple check with a real dataset if the localdatastore is not too slow (it will slow to a crawl REALLY fast, with just as few as 2000 objects in there. See issue #279) and consider using another more tested datastore (for example, Realm is awesome)