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Start adding CoreData-based "reference" counting for statuses 

Prune old statuses that aren't likely to be shown again when scrolling
in timeline table view
This commit is contained in:
Shadowfacts 2020-04-12 23:06:02 -04:00
parent 2c8ba878b7
commit ed37b16463
Signed by untrusted user: shadowfacts
GPG Key ID: 94A5AB95422746E5
6 changed files with 114 additions and 14 deletions
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16
Tusker/CoreData/MastodonCachePersistentStore.swift
View File

@ -37,17 +37,23 @@ class MastodonCachePersistentStore: NSPersistentContainer {
}
}
private func upsert(status: Status) {
private func upsert(status: Status, incrementReferenceCount: Bool) {
if let statusMO = self.status(for: status.id, in: self.backgroundContext) {
statusMO.updateFrom(apiStatus: status, container: self)
if incrementReferenceCount {
statusMO.incrementReferenceCount()
}
} else {
_ = StatusMO(apiStatus: status, container: self, context: self.backgroundContext)
let statusMO = StatusMO(apiStatus: status, container: self, context: self.backgroundContext)
if incrementReferenceCount {
statusMO.incrementReferenceCount()
}
}
}
func addOrUpdate(status: Status, save: Bool = true) {
func addOrUpdate(status: Status, incrementReferenceCount: Bool, save: Bool = true) {
backgroundContext.perform {
self.upsert(status: status)
self.upsert(status: status, incrementReferenceCount: incrementReferenceCount)
if save, self.backgroundContext.hasChanges {
try! self.backgroundContext.save()
}
@ -56,7 +62,7 @@ class MastodonCachePersistentStore: NSPersistentContainer {
func addAll(statuses: [Status], completion: (() -> Void)? = nil) {
backgroundContext.perform {
statuses.forEach(self.upsert(status:))
statuses.forEach { self.upsert(status: $0, incrementReferenceCount: true) }
if self.backgroundContext.hasChanges {
try! self.backgroundContext.save()
}

19
Tusker/CoreData/StatusMO.swift
View File

@ -35,6 +35,7 @@ public final class StatusMO: NSManagedObject {
@NSManaged public var pinned: Bool
@NSManaged public var reblogged: Bool
@NSManaged public var reblogsCount: Int
@NSManaged public var referenceCount: Int
@NSManaged public var sensitive: Bool
@NSManaged public var spoilerText: String
@NSManaged public var uri: String // todo: are both uri and url necessary?
@ -64,12 +65,30 @@ public final class StatusMO: NSManagedObject {
}
}
func incrementReferenceCount() {
referenceCount += 1
}
func decrementReferenceCount() {
referenceCount -= 1
if referenceCount <= 0 {
managedObjectContext!.delete(self)
}
}
public override func prepareForDeletion() {
super.prepareForDeletion()
reblog?.decrementReferenceCount()
}
}
extension StatusMO {
convenience init(apiStatus status: Pachyderm.Status, container: MastodonCachePersistentStore, context: NSManagedObjectContext) {
self.init(context: context)
self.updateFrom(apiStatus: status, container: container)
reblog?.incrementReferenceCount()
}
func updateFrom(apiStatus status: Pachyderm.Status, container: MastodonCachePersistentStore) {

3
Tusker/CoreData/Tusker.xcdatamodeld/Tusker.xcdatamodel/contents
View File

@ -43,6 +43,7 @@
<attribute name="pinned" optional="YES" attributeType="Boolean" usesScalarValueType="YES"/>
<attribute name="reblogged" optional="YES" attributeType="Boolean" usesScalarValueType="YES"/>
<attribute name="reblogsCount" attributeType="Integer 64" defaultValueString="0" usesScalarValueType="YES"/>
<attribute name="referenceCount" attributeType="Integer 64" defaultValueString="0" usesScalarValueType="YES"/>
<attribute name="sensitive" attributeType="Boolean" usesScalarValueType="YES"/>
<attribute name="spoilerText" attributeType="String"/>
<attribute name="uri" attributeType="String"/>
@ -58,6 +59,6 @@
</entity>
<elements>
<element name="Account" positionX="169.21875" positionY="78.9609375" width="128" height="313"/>
<element name="Status" positionX="-63" positionY="-18" width="128" height="403"/>
<element name="Status" positionX="-63" positionY="-18" width="128" height="418"/>
</elements>
</model>

4
Tusker/MastodonCache.swift
View File

@ -59,12 +59,10 @@ class MastodonCache {
func add(status: Status) {
set(status: status, for: status.id)
mastodonController?.persistentContainer.addOrUpdate(status: status)
}
func addAll(statuses: [Status]) {
statuses.forEach(add)
mastodonController?.persistentContainer.addAll(statuses: statuses)
}
// MARK: - Accounts
@ -94,12 +92,10 @@ class MastodonCache {
func add(account: Account) {
set(account: account, for: account.id)
mastodonController?.persistentContainer.addOrUpdate(account: account)
}
func addAll(accounts: [Account]) {
accounts.forEach(add)
mastodonController?.persistentContainer.addAll(accounts: accounts)
}
// MARK: - Relationships

2
Tusker/SceneDelegate.swift
View File

@ -109,6 +109,8 @@ class SceneDelegate: UIResponder, UIWindowSceneDelegate {
// Called as the scene transitions from the foreground to the background.
// Use this method to save data, release shared resources, and store enough scene-specific state information
// to restore the scene back to its current state.
try! scene.session.mastodonController?.persistentContainer.viewContext.save()
}
func activateAccount(_ account: LocalData.UserAccountInfo) {

84
Tusker/Screens/Timeline/TimelineTableViewController.swift
View File

@ -19,6 +19,9 @@ class TimelineTableViewController: EnhancedTableViewController {
var newer: RequestRange?
var older: RequestRange?
private var prevScrollViewContentOffset: CGPoint?
private var scrollViewDirection: CGFloat = 0
init(for timeline: Timeline, mastodonController: MastodonController) {
self.timeline = timeline
self.mastodonController = mastodonController
@ -38,6 +41,17 @@ class TimelineTableViewController: EnhancedTableViewController {
fatalError("init(coder:) has not been implemented")
}
deinit {
// decrement reference counts of any statuses we still have
// if the app is currently being quit, this will not affect the persisted data because
// the persistent container would already have been saved in SceneDelegate.sceneDidEnterBackground(_:)
for segment in timelineSegments {
for (id, _) in segment {
mastodonController.persistentContainer.status(for: id)?.decrementReferenceCount()
}
}
}
func statusID(for indexPath: IndexPath) -> String {
return timelineSegments[indexPath.section][indexPath.row].id
}
@ -59,7 +73,6 @@ class TimelineTableViewController: EnhancedTableViewController {
let request = Client.getStatuses(timeline: timeline)
mastodonController.run(request) { response in
guard case let .success(statuses, pagination) = response else { fatalError() }
// self.mastodonController.cache.addAll(statuses: statuses)
// todo: possible race condition here? we update the underlying data before waiting to reload the table view
self.timelineSegments.insert(statuses.map { ($0.id, .unknown) }, at: 0)
self.newer = pagination?.newer
@ -96,6 +109,59 @@ class TimelineTableViewController: EnhancedTableViewController {
// MARK: - Table view delegate
override func tableView(_ tableView: UITableView, willDisplay cell: UITableViewCell, forRowAt indexPath: IndexPath) {
// when scrolling upwards, decrement reference counts for old statuses, if necessary
if scrollViewDirection < 0 {
if indexPath.section <= timelineSegments.count - 2 {
// decrement ref counts for all sections below the section below the current section
// (e.g., there exist sections 0, 1, 2 and we're currently scrolling upwards in section 0, we want to remove section 2)
// todo: this is in the hot path for scrolling, possibly move this to a background thread?
let sectionsToRemove = indexPath.section + 1..<timelineSegments.count
for section in sectionsToRemove {
for (id, _) in timelineSegments.remove(at: section) {
mastodonController.persistentContainer.status(for: id)?.decrementReferenceCount()
}
}
// see below comment about DispatchQueue.main.async
DispatchQueue.main.async {
UIView.performWithoutAnimation {
tableView.deleteSections(IndexSet(sectionsToRemove), with: .none)
}
}
} else {
// we are scrolling in the last or second to last section
// grab the last section and, if there is more than one page in the last section
// (we never want to remove the only page in the last section unless there is another section between it and the user),
// remove the last page and decrement reference counts
let pageSize = 20 // todo: this should come from somewhere in Pachyderm
let lastSection = timelineSegments.last!
if lastSection.count > 2 * pageSize,
indexPath.row < lastSection.count - (2 * pageSize) {
// todo: this is in the hot path for scrolling, possibly move this to a background thread?
let statusesToRemove = lastSection[lastSection.count - pageSize..<lastSection.count]
for (id, _) in statusesToRemove {
mastodonController.persistentContainer.status(for: id)?.decrementReferenceCount()
}
timelineSegments[timelineSegments.count - 1].removeLast(20)
let removedIndexPaths = (lastSection.count - 20..<lastSection.count).map { IndexPath(row: $0, section: timelineSegments.count - 1) }
// Removing this DispatchQueue.main.async call causes things to break when scrolling
// back down towards the removed rows. There would be a index out of bounds crash
// because, while we've already removed the statuses from our model, the table view doesn't seem to know that.
// It seems like tableView update calls made from inside tableView(_:willDisplay:forRowAt:) are silently ignored.
// Calling tableView.numberOfRows(inSection: 0) when trapped in the debugger after the aforementioned IOOB
// will produce an incorrect value (it will be some multiple of pageSize too high).
// Deferring the tableView update until the next runloop iteration seems to solve that.
DispatchQueue.main.async {
UIView.performWithoutAnimation {
tableView.deleteRows(at: removedIndexPaths, with: .none)
}
}
}
}
}
// load older statuses, if necessary
if indexPath.section == timelineSegments.count - 1,
indexPath.row == timelineSegments[indexPath.section].count - 1 {
guard let older = older else { return }
@ -104,7 +170,6 @@ class TimelineTableViewController: EnhancedTableViewController {
mastodonController.run(request) { response in
guard case let .success(newStatuses, pagination) = response else { fatalError() }
self.older = pagination?.older
// self.mastodonController.cache.addAll(statuses: newStatuses)
let newRows = self.timelineSegments.last!.count..<(self.timelineSegments.last!.count + newStatuses.count)
let newIndexPaths = newRows.map { IndexPath(row: $0, section: self.timelineSegments.count - 1) }
self.timelineSegments[self.timelineSegments.count - 1].append(contentsOf: newStatuses.map { ($0.id, .unknown) })
@ -138,7 +203,6 @@ class TimelineTableViewController: EnhancedTableViewController {
mastodonController.run(request) { response in
guard case let .success(newStatuses, pagination) = response else { fatalError() }
self.newer = pagination?.newer
// self.mastodonController.cache.addAll(statuses: newStatuses)
self.timelineSegments[0].insert(contentsOf: newStatuses.map { ($0.id, .unknown) }, at: 0)
if let newer = pagination?.newer {
@ -163,6 +227,15 @@ class TimelineTableViewController: EnhancedTableViewController {
}
}
// Mark: Scroll View Delegate
override func scrollViewDidScroll(_ scrollView: UIScrollView) {
if let prev = prevScrollViewContentOffset {
scrollViewDirection = scrollView.contentOffset.y - prev.y
}
prevScrollViewContentOffset = scrollView.contentOffset
}
@objc func composePressed(_ sender: Any) {
compose()
}
@ -192,7 +265,10 @@ extension TimelineTableViewController: UITableViewDataSourcePrefetching {
func tableView(_ tableView: UITableView, cancelPrefetchingForRowsAt indexPaths: [IndexPath]) {
for indexPath in indexPaths {
guard let status = mastodonController.persistentContainer.status(for: statusID(for: indexPath)) else { continue }
// todo: this means when removing cells, we can't cancel prefetching
// is this an issue?
guard indexPath.section < timelineSegments.count, indexPath.row < timelineSegments[indexPath.section].count,
let status = mastodonController.persistentContainer.status(for: statusID(for: indexPath)) else { continue }
ImageCache.avatars.cancelWithoutCallback(status.account.avatar)
for attachment in status.attachments {
ImageCache.attachments.cancelWithoutCallback(attachment.url)