(Question) How to select multiple objects by id (@PrimaryKey)?

[AlbertVilaCalvo]

Hi. I have a RealmObject subclass called Article which has an id field (it's and int and also a @PrimaryKey). I would like to pass to a query a list of ints (a Set<>, int[], or whatever) of article id's and retrieve only those articles.

In SQL would be like this:

SELECT *
FROM `table`
where ID in (5263, 5625, 5628, 5621) 

I've seen it's possible to do this in iOS in this StackOverflow question.

How can I do this in Android? Thanks!

[knighty]

Unfortunately, Realm java currently has no support for this so you have to build up an OR query manually to achieve the same thing.

RealmQuery<MyRealmObject> query = realm.where(MyRealmObject.class);
int i = 0;
for (int id : ids) {
    if (i++ > 0)
        query = query.or();
    query = query.equalsTo("id", id);
}

query.beginGroup(); and query.endGroup(); can be used around the for loop if you need to select on some other parameters too.

[zaki50]

@AlbertVilaCalvo As @knighty said, Realm Java does not support IN query.

The code for building the query can be a bit shorter.

RealmQuery<MyRealmObject> query = realm.where(MyRealmObject.class);
for (int id : ids) {
        query = query.or().equalsTo("id", id);
}

IN operator issue is tracked as #841 and also #1280 is helpful.

I'll close this issue as a duplicate of #841. If you have further questions, feel free to reopen this or create new issue.

[AlbertVilaCalvo]

Thank you all. Because I want to return an empty RealmResults<Article> if the list of ids is empty, that's what I ended up doing:

Set<Integer> articleIds = this.getArticleIds();
RealmQuery<Article> query = realm.where(Article.class);
if (articleIds.size() == 0) {
    // We want to return an empty list if the basket is empty. Just search for an id that
    // does not exist.
    query = query.equalTo("id", -30000);
} else {
    int i = 0;
    for (int id : articleIds) {
        // The or() operator requires left hand and right hand elements. If articleIds had
        // only one element then it would crash ("Missing right-hand side of OR")
        if (i++ > 0) {
            query = query.or();
        }
        query = query.equalTo("id", id);
    }
}