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Don't use shared background context for fetching item counts 

A significant fraction of the time was spent waiting for the background
context to be available, before the count could even be started. Since
the counts don't need to use the shared background context, let them
each use their own context to avoid contention.
This commit is contained in:
Shadowfacts 2022-09-10 14:14:31 -04:00
parent 57cc5ac5a5
commit 6881441671
2 changed files with 11 additions and 9 deletions
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2
Reader.xcodeproj/xcshareddata/xcschemes/Reader.xcscheme
View File

@ -77,7 +77,7 @@
</CommandLineArgument>
<CommandLineArgument
argument = "-com.apple.CoreData.SQLDebug 1"
isEnabled = "YES">
isEnabled = "NO">
</CommandLineArgument>
</CommandLineArguments>
<EnvironmentVariables>

18
Reader/Screens/Home/HomeCollectionViewCell.swift
View File

@ -14,7 +14,7 @@ private let signposter = OSSignposter(subsystem: "net.shadowfacts.Reader", categ
class HomeCollectionViewCell: UICollectionViewListCell {
private var currentItemListType: ItemListType?
private var currentItemCountTask: Task<Void, Never>?
private var itemCount: Int?
#if !targetEnvironment(macCatalyst)
@ -31,12 +31,11 @@ class HomeCollectionViewCell: UICollectionViewListCell {
override func prepareForReuse() {
super.prepareForReuse()
currentItemCountTask?.cancel()
itemCount = nil
}
func updateUI(item: ItemListType, persistentContainer: PersistentContainer) {
self.currentItemListType = item
var config = UIListContentConfiguration.valueCell()
config.text = item.title
if let itemCount {
@ -45,10 +44,10 @@ class HomeCollectionViewCell: UICollectionViewListCell {
config.secondaryTextProperties.color = .tintColor
self.contentConfiguration = config
Task(priority: .userInitiated) {
let state = signposter.beginInterval("fetch count", id: signposter.makeSignpostID())
currentItemCountTask = Task(priority: .userInitiated) {
let state = signposter.beginInterval("fetch count", id: signposter.makeSignpostID(), "\(String(item.hashValue, radix: 16), privacy: .public)")
if let count = await fetchCount(item: item, in: persistentContainer),
self.currentItemListType == item {
!Task.isCancelled {
self.itemCount = count
config.secondaryText = count.formatted(.number)
self.contentConfiguration = config
@ -62,9 +61,12 @@ class HomeCollectionViewCell: UICollectionViewListCell {
return nil
}
return await withCheckedContinuation({ continuation in
let context = persistentContainer.backgroundContext
context.perform {
let state = signposter.beginInterval("waiting to perform", id: signposter.makeSignpostID(), "\(String(item.hashValue, radix: 16), privacy: .public)")
persistentContainer.performBackgroundTask { context in
signposter.endInterval("waiting to perform", state)
let state = signposter.beginInterval("count", id: signposter.makeSignpostID(), "\(String(item.hashValue, radix: 16), privacy: .public)")
let count = try? context.count(for: request)
signposter.endInterval("count", state)
continuation.resume(returning: count)
}
})