GQL query where field is not null

Question

I have an entity kind called Account. One of the fields is a String named selfie, which is basically the url to a selfie uploaded by a user. I want to fetch for users who have a selfie (so if a user does not have a selfie they should not be included in the result set). I have the following query. but it won't work because I have "NULL" as a string. What is the correct way for doing this? Again, I only want users who have selfies.

Filter selfie = new FilterPredicate("selfie", FilterOperator.GREATER_THAN, "NULL");
Query query = new Query(Account.class.getSimpleName()).setFilter(selfie);
FetchOptions options = FetchOptions.Builder.withLimit(30);
DatastoreService datastore = DatastoreServiceFactory.getDatastoreService();
QueryResultList<Entity> entities = datastore.prepare(query).asQueryResultList(options);

Also I am open to a JDO/JPA way of doing this on App-Engine (but it must work on App-Engine).

score 5 · Answer 1 · answered Dec 25 '16 at 05:00

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After some trial and error on https://console.cloud.google.com/datastore/entities/query/gql

I found this work around expression for IS NOT NULL:

> NULL

Example:

Select * from State where customer_id > NULL

I haven't tested this on a field with negative values.

answered Dec 25 '16 at 05:00

Darian Hickman

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Surprised that IS NOT NULL is not supported in GQL. – Darian Hickman Dec 25 '16 at 05:01

score 1 · Accepted Answer · edited May 23 '17 at 12:32

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This should be as simple as

Filter selfie = new FilterPredicate("selfie", FilterOperator.NOT_EQUAL, null);

where you actually pass the Java null value (not a String) and filter with not equals (see https://stackoverflow.com/a/22200137).

Personally, I've been using JDO for my datastore management, which has its pros and cons. Let me know if you'd like to see a solution using JDO as well. Cheers!

edited May 23 '17 at 12:32

Community

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answered Feb 17 '15 at 22:12

Mr. Kevin Thomas

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@Kevin Thomas Can you let us know how to do the same with JDO as well.? Thanks. – Malleswari Apr 21 '15 at 12:42
The original poster asked for a GQL solution. That's what I'm looking for, too. – Vince Jun 05 '20 at 07:39

GQL query where field is not null

2 Answers2