how to apply date filter on ancestor query

Question

I have two entity model Student and attendance such that each attendance entity has associated student parent.

Attendance model:

@Entity         


        

Answer 1

Just wanted to add to konqi's answer based on comments:

If you are using Cloud Endpoints with Android Studio you must first switch to "project" view in your navigation panel, then navigate to your "backend" folder then src->main->webapp->WEB-INF and then in that folder you must manually create a datastore-indexes.xml file. Here is what yours would look like:

<?xml version="1.0" encoding="utf-8"?>
<datastore-indexes autoGenerate="true">
    <!-- NOTE: Not necessary to create composite indexes here for single property indices b.c. they are build in.-->

    <!-- If you do not specify direction, default is: direction="asc" -->

    <datastore-index kind="Attendance" ancestor="true" source="manual">
        <property name="date" direction="asc"/>
    </datastore-index>

</datastore-indexes>

Answer 2

Answering Question 1:

Appengine uses UTC timestamps. Therefor your timestamp is converted from your time zone to UTC. It is still the same date and time though. During output you need to consider that the timestamp may contain the timezone and format / calculate the local time accordingly.

Answering Question 2:

You have all the information you need in your error. If you add

<datastore-index kind="Attendance" ancestor="true" source="manual">
    <property name="date" direction="asc"/>
</datastore-index>

to your datastore-indexes.xml your query should work. If the file doesn't exist yet, create it under src/main/webapp/WEB-INF/datastore-indexes.xml, next to your web.xml and appengine-web.xml files. You can find an example on this page.

As for why: The answer with this error is always: Because datastore requires a composite index for this query.