Got this from filtering a list with multiple filters and I don’t see how it will help performance? S...

# intellij

[bob]

Got this from filtering a list with multiple filters and I don’t see how it will help performance?
Since I need to go through each item the exact same steps (only in a different order) in the two variants.
But using a sequence I need to first convert it into a sequence. Why is this a performance boost?

The code:

features
    .filter { it.segment.contains(value) }
    .filter { inDateRange(it.date) }
    .filter { inVersionRange(it.appVersion) }
    .filter { it.osVersion.contains(Build.VERSION.SDK_INT) }
    .map { it.identifier }

[Mike]

First, toSequence for a collection uses the iterator on the existing collection (IIRC), so no real cost here.

If you leave it as a list, your code will create 5 new lists, one after each filter.

A sequence processes each element through all the steps (or at least until it gets filtered out), so it only creates one list.

That's where the gain can come from.

[bob]

Thank you for that clarification! 🙏

[Paul Woitaschek]

Yet if your features list does not countain a lot of elements there is no performance to gain

[Paul Woitaschek]

I use sequences only if there is some way of early abort

[Paul Woitaschek]

like .sequence-filter-filter-filter-first()

[bob]

Yeah, I've got a shortlist of 20 items and just a bunch of filters. And even if I use a sequence, I will perform the same amount of filtering calls.
But now I can make an informed decision if I want to make the switch or not.
So I'll stick with the list for now.