Delete articles and statuses from feeds no longer subscribed-to. At startup. Fix #899.

Frameworks/Account/Account.swift

@@ -254,6 +254,7 @@ public final class Account: DisplayNameProvider, UnreadCountProvider, Container,
 		pullObjectsFromDisk()
 		
 		DispatchQueue.main.async {
+			self.database.cleanupDatabaseAtStartup(subscribedToFeedIDs: self.flattenedFeeds().feedIDs())
 			self.fetchAllUnreadCounts()
 		}
 

Frameworks/ArticlesDatabase/ArticlesDatabase.swift

@@ -152,6 +152,15 @@ public final class ArticlesDatabase {
 	public func emptyCaches() {
 		articlesTable.emptyCaches()
 	}
+
+	// MARK: - Cleanup
+
+	// These are to be used only at startup. These are to prevent the database from growing forever.
+
+	/// Calls the various clean-up functions.
+	public func cleanupDatabaseAtStartup(subscribedToFeedIDs: Set<String>) {
+		articlesTable.deleteArticlesNotInSubscribedToFeedIDs(subscribedToFeedIDs)
+	}
 }
 
 // MARK: - Private

Frameworks/ArticlesDatabase/ArticlesTable.swift

@@ -423,6 +423,31 @@ final class ArticlesTable: DatabaseTable {
 			self.databaseArticlesCache = [String: DatabaseArticle]()
 		}
 	}
+
+	// MARK: - Cleanup
+
+	/// Delete articles from feeds that are no longer in the current set of subscribed-to feeds.
+	/// This deletes from the articles and articleStatuses tables,
+	/// and, via a trigger, it also deletes from the search index.
+	func deleteArticlesNotInSubscribedToFeedIDs(_ feedIDs: Set<String>) {
+		if feedIDs.isEmpty {
+			return
+		}
+		queue.run { (database) in
+			let placeholders = NSString.rs_SQLValueList(withPlaceholders: UInt(feedIDs.count))!
+			let sql = "select articleID from articles where feedID not in \(placeholders);"
+			let parameters = Array(feedIDs) as [Any]
+			guard let resultSet = database.executeQuery(sql, withArgumentsIn: parameters) else {
+				return
+			}
+			let articleIDs = resultSet.mapToSet{ $0.string(forColumn: DatabaseKey.articleID) }
+			if articleIDs.isEmpty {
+				return
+			}
+			self.removeArticles(articleIDs, database)
+			self.statusesTable.removeStatuses(articleIDs, database)
+		}
+	}
 }
 
 // MARK: - Private
@@ -730,6 +755,10 @@ private extension ArticlesTable {
 		// Drop Articles that we can ignore.
 		return Set(articles.filter{ !statusIndicatesArticleIsIgnorable($0.status) })
 	}
+
+	func removeArticles(_ articleIDs: Set<String>, _ database: FMDatabase) {
+		deleteRowsWhere(key: DatabaseKey.articleID, equalsAnyValue: Array(articleIDs), in: database)
+	}
 }
 
 private extension Set where Element == ParsedItem {

Frameworks/ArticlesDatabase/StatusesTable.swift

@@ -134,6 +134,12 @@ final class StatusesTable: DatabaseTable {
 
 		return d
 	}
+
+	// MARK: - Cleanup
+
+	func removeStatuses(_ articleIDs: Set<String>, _ database: FMDatabase) {
+		deleteRowsWhere(key: DatabaseKey.articleID, equalsAnyValue: Array(articleIDs), in: database)
+	}
 }
 
 // MARK: - Private