Malien

func liftOptional<each Ts>(_ values: repeat (each Ts)?) -> (repeat each Ts)? {
    for value in repeat each values {
        if value == nil { return nil }
    }
    return (repeat (each values)!)
}

struct PartialResult<each Element> {
    var contents: (repeat (each Element)?)

Malien

Was trying to see which method for bulk retrieving data from IndexedDB would perform the best on different data distribution.

Key takeaways:

• Use Promise.all(keys.map(key => store.get(key))) for most cases (random lookups or even contigiuos-ish cases are mostly fine).
• Use store.get(KeyRange.bound(lower, upper) when you know you are interested in a contigious range.
• Avoid cursor API whenever possible. If you are fine with a bit more memory usage, just fetch everything via getAll() and do filtering afterwards.
• The chunked retrieval is honestly pretty descent, for contigious/contigiuos-ish lookups.
• When the loads start to look like full-table retrieval (ie. retrieving 80% of the records), Promise.all starts to fall behind. Consider doing full-table retrieval, or, if you are memory constrained, chunked iteration/full-table scan via getAll or cursor API.

Duh.