Iterating live result during update (write) is slow

Problem

Perfoming the following operations: Given a dataset of 1000 elements, update matching string with a new string Takes a ridiculously huge amount time And the time complexity grows dramatically when increasing the dataset to 10 000 elements

Code snippet

    override suspend fun update(param: String, objectToInsert: NewsReportDto) {
        realm.query<NewsReportDto>("title == $0", param)
            .find()
            .forEach { oldNewsReportDto ->
                realm.write {
                    findLatest(oldNewsReportDto)?.apply {
                        title = objectToInsert.title
                        description = objectToInsert.description
                    }
                }
            }
    }

Link to this update method source code Link to the data generator

Performance result

Let me know if i’m doing something wrong, the corresponding update query for Room

        "UPDATE newsReport " +
                "SET title = :newTitle," +
                "description = :newDescription " +
                "WHERE title = :title"

takes very little time for example, 20 miliseconds for 1k elements, and 20 miliseconds for 10k elements

[rorbech]

@konnovdev I have been digging a bit and what happens is that the underlying query is most likely re-run when you update the objects, so for now the best thing is probably to iterate the stable result from the frozen realm.query. I will have to dig a bit further to understand the details and, if the hypothesis is right, the options of providing a stable results for these use cases.

[rorbech]

Closing this issue as the various root causes of the lower speed has been explained, but created #914 to enhance the API to provide a stable result for fast and predictable iteration.