Added limit and offset parameters to Database#getMessagesWithMedia in order to prevent high memory usage in downloadMedia.

src/main/kotlin/de/fabianonline/telegram_backup/Database.kt

@@ -98,10 +98,14 @@ class Database private constructor(var client: TelegramClient) {
 
 		}
 
-	fun getMessagesWithMedia(): LinkedList<TLMessage?> {
+	fun getMessagesWithMediaCount() = queryInt("SELECT COUNT(*) FROM messages WHERE has_media=1")
+
+	fun getMessagesWithMedia(limit: Int = 0, offset: Int = 0): LinkedList<TLMessage?> {
 		try {
 			val list = LinkedList<TLMessage?>()
-			val rs = stmt!!.executeQuery("SELECT data FROM messages WHERE has_media=1")
+			var query = "SELECT data FROM messages WHERE has_media=1 ORDER BY id"
+			if (limit > 0) query += " LIMIT ${limit} OFFSET ${offset}"
+			val rs = stmt!!.executeQuery(query)
 			while (rs.next()) {
 				list.add(bytesToTLMessage(rs.getBytes(1)))
 			}

src/main/kotlin/de/fabianonline/telegram_backup/DownloadManager.kt

@@ -309,38 +309,46 @@ class DownloadManager(internal var client: TelegramClient?, p: DownloadProgressI
 			logger.debug("Found {} messages", ids.size)
 			downloadMessages(ids, null, source_type=MessageSource.NORMAL)
 		}
-
+		
-		val messages = this.db!!.getMessagesWithMedia()
+		var offset = 0
-		logger.debug("Database returned {} messages with media", messages.size)
+		val limit = 1000
-		prog!!.onMediaDownloadStart(messages.size)
+		val message_count = this.db!!.getMessagesWithMediaCount()
-		for (msg in messages) {
+		prog!!.onMediaDownloadStart(message_count)
-			if (msg == null) continue
+		while (true) {
-			val m = FileManagerFactory.getFileManager(msg, user!!, client!!)
+			logger.debug("Querying messages with media, limit={}, offset={}", limit, offset)
-			logger.trace("message {}, {}, {}, {}, {}",
+			val messages = this.db!!.getMessagesWithMedia(limit=limit, offset=offset)
-				msg.getId(),
+			if (messages.size == 0) break
-				msg.getMedia().javaClass.getSimpleName().replace("TLMessageMedia", "…"),
+			offset += limit
-				m!!.javaClass.getSimpleName(),
+			logger.debug("Database returned {} messages with media", messages.size)
-				if (m.isEmpty) "empty" else "non-empty",
+			
-				if (m.downloaded) "downloaded" else "not downloaded")
+			for (msg in messages) {
-			if (m.isEmpty) {
+				if (msg == null) continue
-				prog!!.onMediaDownloadedEmpty()
+				val m = FileManagerFactory.getFileManager(msg, user!!, client!!)
-			} else if (m.downloaded) {
+				logger.trace("message {}, {}, {}, {}, {}",
-				prog!!.onMediaAlreadyPresent(m)
+					msg.getId(),
-			} else if (IniSettings.max_file_age!=null && (System.currentTimeMillis() / 1000) - msg.date > IniSettings.max_file_age * 24 * 60 * 60) {
+					msg.getMedia().javaClass.getSimpleName().replace("TLMessageMedia", "…"),
-				prog!!.onMediaTooOld()
+					m!!.javaClass.getSimpleName(),
-			} else {
+					if (m.isEmpty) "empty" else "non-empty",
-				try {
+					if (m.downloaded) "downloaded" else "not downloaded")
-					val result = m.download()
+				if (m.isEmpty) {
-					if (result) {
+					prog!!.onMediaDownloadedEmpty()
-						prog!!.onMediaDownloaded(m)
+				} else if (m.downloaded) {
-					} else {
+					prog!!.onMediaAlreadyPresent(m)
+				} else if (IniSettings.max_file_age!=null && (System.currentTimeMillis() / 1000) - msg.date > IniSettings.max_file_age * 24 * 60 * 60) {
+					prog!!.onMediaTooOld()
+				} else {
+					try {
+						val result = m.download()
+						if (result) {
+							prog!!.onMediaDownloaded(m)
+						} else {
+							prog!!.onMediaSkipped()
+						}
+					} catch (e: TimeoutException) {
+						// do nothing - skip this file
 						prog!!.onMediaSkipped()
 					}
-				} catch (e: TimeoutException) {
-					// do nothing - skip this file
-					prog!!.onMediaSkipped()
 				}
-
 			}
 		}
 		prog!!.onMediaDownloadFinished()