Using a PropertyQuery on an @Id field

[RobbWatershed]

Using ObjectBox v3.0.1

As I'm building rather complex queries, I sometimes need to extract IDs to intersect them using Java streams & collections.

I'm trying to do that using PropertyQueries, e.g.

QueryBuilder<GroupItem> customGContentQB = store.boxFor(GroupItem.class).query();
customGContentQB.link(GroupItem_.group).equal(Group_.grouping, Grouping.CUSTOM.getId());
return customGContentQB.build().property(GroupItem_.contentId).findLongs();

Where GroupItem_.contentId is inside a ToOne relation

@Entity
public class GroupItem {

    @Id
    public long id;
    public ToOne<Content> content;
    public ToOne<Group> group;
    public int order;
}

When doing that, ObjectBox crashes with the following message

    Process: me.myapp.debug, PID: 6964
    java.lang.IllegalArgumentException: Property "contentId" is of type Relation, but we expected a property of type Long in this context.
        at io.objectbox.query.PropertyQuery.nativeFindLongs(Native Method)
        at io.objectbox.query.PropertyQuery.lambda$findLongs$1(PropertyQuery.java:209)
        at io.objectbox.query.PropertyQuery.$r8$lambda$_kSlTz290CY5pQO1ceZRF6rRKRU(Unknown Source:0)
        at io.objectbox.query.PropertyQuery$$ExternalSyntheticLambda1.call(Unknown Source:2)
        at io.objectbox.BoxStore.callInReadTx(BoxStore.java:936)
        at io.objectbox.BoxStore.callInReadTxWithRetry(BoxStore.java:882)
        at io.objectbox.query.Query.callInReadTx(Query.java:294)
        at io.objectbox.query.PropertyQuery.findLongs(PropertyQuery.java:208)
        at me.myapp.database.ObjectBoxDB.selectCustomGroupedContent(ObjectBoxDB.java:1504)

As that case isn't documented, I wondered if it is a bug, uncharted territory, or if it could get a fix.

For instance I wouldn't mind using something like PropertyQuery.findTargetIds instead of PropertyQuery.findLongs if it could make its way to the proper result.

If it is not supported at all, could you please make the message more explicit (e.g. "Querying relation Ids with a PropertyQuery is not supported") ?

---

PS : Current workaround I found is to code my query the other way around, but I hate to use these double links

QueryBuilder<Content> customContentQB = store.boxFor(Content.class).query();
customContentQB.link(Content_.groupItems).link(GroupItem_.group).equal(Group_.grouping, Grouping.CUSTOM.getId());
return customContentQB.build().property(Content_.id).findLongs();

[greenrobot-team]

There is findIds() for a regular query, does that work for you (e.g. re-write the query to return Content objects, but then use findIds() instead of find())?

[no-response]

Without additional information, we are unfortunately not sure how to resolve this issue. Therefore this issue has been automatically closed. Feel free to comment with additional details and we can re-open this issue.

[RobbWatershed]

First of all, sorry for the delay.

There is findIds() for a regular query, does that work for you (e.g. re-write the query to return Content objects, but then use findIds() instead of find())?

Do you mean something like that ?

builder.link(GroupItem_.content).build().findIds()

... because when I do so, ObjectBox tells me

java.lang.IllegalStateException: This call is not supported on sub query builders (links)
        at io.objectbox.query.QueryBuilder.verifyNotSubQuery(QueryBuilder.java:277)
        at io.objectbox.query.QueryBuilder.build(QueryBuilder.java:263)

I'm ending up either coding my query the other way around, when there's a @Backlink available, or streaming entire objects to extract IDs and build an array with them. Neither of these solutions are performant ☹️

Really, having a specific PropertyQuery accessor for IDs would be much simpler and efficient to use.

[RobbWatershed]

@greenrobot-team please consider reopening that one. Thanks in advance

[greenrobot]

Property "contentId" is of type Relation, but we expected a property of type Long in this context.
        at io.objectbox.query.PropertyQuery.nativeFindLongs(Native Method)

This actually looks like something that makes sense to allow...

[greenrobot]

Relation properties are now allowed for PropertyQuery using long internally. This will be part of the next release (no date yet).

[RobbWatershed]

Fan-tas-tic ! Thanks @greenrobot

[greenrobot-team]

Also closing as fixed, will ship with the next release.

[greenrobot-team]

Fix now available with release 3.5.0! Let us know if there are issues.