Performance - Overhead of using Realm objects

Currently, using Realm in a scenario which require a lot of calls through the C++/JS boundary (i.e. in a tight loop), can totally kill the performance of an app.

We did some tests and for example, just accessing something like

results[0].myprop

was >200x slower with Realm objects than normal JS array of objects (which you’d get after running a query on other databases).

Some possible solutions:

• Graal.js in theory could help with that, but it seems that node extensions are not optimized at this point

• Automatic caching of retrieved data (datomic does something similar)

• Using something like JSON.parse(JSON.stringify(results)) instead of realm collections and objects - slow and ugly, last-resort hack

[l7x]

Yeah, I explained that in my reply to @cristianoccazinsp. This test is hitting the previously mentioned results[0].myprop access (which also reveals another issue which we noticed and you mentioned - if you access results[0] multiple times, why not return the same object (it’s a “live” object anyway), instead of creating a new one?). Modifying the test to only test hitting a lot of properties in a loop is trivial - just copy&paste a property access many times in the loop.

https://github.com/realm/realm-js/issues/2782#issuecomment-608443330 https://github.com/realm/realm-js/issues/2782#issuecomment-608453197

[l7x]

Realm is more column oriented and using mmap’ed files. You can find more info about design on their website.

In a way, Realm is more similar to those “deferred” Django properties than typical access patterns, bit with more efficient fetching and less efficient caching.

I do have some ideas about some helper methods which may make converting to POJOs less messy, but I’m in a hurry now, I’ll write them here later.