How do we drop and recreate the entire collection without impacting the reading thread?

[vtharmalingam]

Hi,

I have a use case wherein I need to drop my table/collection every 30 minutes (or so) and recreate it with new data. The important requirement is that the other thread that reads should not run out of data (from the said table) at any moment. The main thread should drop and recreate the collection without impacting the reading thread, which has it's own realm instance.

So I have two Qs here:

1. Can I do the drop operation inside like this: realm_instance. rite([&] { //drop the collection } ?
2. Secondly, I am unable to figure out a specific function that drops the given collection. I know there exists a function called "remove," but that only removes one record and not the entire table.

BTW, my use case can even let me build a new collection while loading the new data, so that can swap the name post-loading, if that is an option available too.

Please advise. Thanks for your help in advance.

Regards,
Tharma

[vtharmalingam]

@leemaguire : Can you please throw some lights on the above? I am actually stuck with that. Thanks for your help.

[leemaguire]

Hi @vtharmalingam, that function is not currently exposed. I'll get a PR up that exposes the functionality soon.

[vtharmalingam]

Thank you very much for the update, @leemaguire. Really appreciated.

[vtharmalingam]

@leemaguire :
Could you please advise me if there's any method available today to clear a collection during a write operation?

[leemaguire]

For the meantime you can do this until we expose the correct API to remove all objects:

auto res = realm.objects<AllTypesObject>();
            realm.write([&] {
                while (realm.objects<AllTypesObject>().size() > 0) {
                    auto obj = realm.objects<AllTypesObject>()[0];
                    realm.remove(obj);
                }
            });

[vtharmalingam]

Sure, this is really helpful. Thank you @leemaguire, as always!

[turninX]

Hi,
I wonder if there is a exposed API to remove all objects in new version?
I tried this and the data was indeed cleared, but I found that the size of the database file did not decrease. Is there any way to reduce the file size while clearing the data?

auto res = realm.objects<AllTypesObject>();
            realm.write([&] {
                while (realm.objects<AllTypesObject>().size() > 0) {
                    auto obj = realm.objects<AllTypesObject>()[0];
                    realm.remove(obj);
                }
            });

Thanks