Empty the database articles cache when NetNewsWire moves to the background. This helps prevent the cache from growing forever.

Frameworks/Account/Account.swift

@@ -615,6 +615,11 @@ public final class Account: DisplayNameProvider, UnreadCountProvider, Container,
 		}
 	}
 
+	/// Empty caches that can reasonably be emptied. Call when the app goes in the background, for instance.
+	func emptyCaches() {
+		database.emptyCaches()
+	}
+
 	// MARK: - Container
 
 	public func flattenedFeeds() -> Set<Feed> {

Frameworks/Account/AccountManager.swift

@@ -223,6 +223,15 @@ public final class AccountManager: UnreadCountProvider {
 		}
 	}
 
+	// MARK: - Caches
+
+	/// Empty caches that can reasonably be emptied — when the app moves to the background, for instance.
+	public func emptyCaches() {
+		for account in accounts {
+			account.emptyCaches()
+		}
+	}
+
 	// MARK: - Notifications
 	
 	@objc dynamic func unreadCountDidChange(_ notification: Notification) {

Frameworks/ArticlesDatabase/ArticlesDatabase.swift

@@ -143,6 +143,14 @@ public final class ArticlesDatabase {
 	public func mark(_ articles: Set<Article>, statusKey: ArticleStatus.Key, flag: Bool) -> Set<ArticleStatus>? {
 		return articlesTable.mark(articles, statusKey, flag)
 	}
+
+	// MARK: - Caches
+
+	/// Call to free up some memory. Should be done when the app is backgrounded, for instance.
+	/// This does not empty *all* caches — just the ones that are empty-able.
+	public func emptyCaches() {
+		articlesTable.emptyCaches()
+	}
 }
 
 // MARK: - Private

Frameworks/ArticlesDatabase/ArticlesTable.swift

@@ -411,6 +411,14 @@ final class ArticlesTable: DatabaseTable {
 			}
 		}
 	}
+
+	// MARK: - Caches
+
+	func emptyCaches() {
+		queue.run { _ in
+			self.databaseArticlesCache = [String: DatabaseArticle]()
+		}
+	}
 }
 
 // MARK: - Private

Mac/AppDelegate.swift

@@ -224,9 +224,8 @@ class AppDelegate: NSObject, NSApplicationDelegate, NSUserInterfaceValidations,
 	}
 	
 	func applicationDidResignActive(_ notification: Notification) {
-
 		TimelineStringFormatter.emptyCaches()
-
+		AccountManager.shared.emptyCaches()
 		saveState()
 	}