From eb1f731b9d9a180dd16590b2e52c55187febe737 Mon Sep 17 00:00:00 2001
From: Fabian Schlenz <mail@fabianonline.de>
Date: Mon, 5 Mar 2018 06:39:30 +0100
Subject: [PATCH] DB_Update_9 now uses chunks of messages to (massively) reduce
 the amount of heap space needed.

---
 .../telegram_backup/DatabaseUpdates.kt        | 33 ++++++++++++-------
 1 file changed, 21 insertions(+), 12 deletions(-)

diff --git a/src/main/kotlin/de/fabianonline/telegram_backup/DatabaseUpdates.kt b/src/main/kotlin/de/fabianonline/telegram_backup/DatabaseUpdates.kt
index 583b4a9..4ddfe59 100644
--- a/src/main/kotlin/de/fabianonline/telegram_backup/DatabaseUpdates.kt
+++ b/src/main/kotlin/de/fabianonline/telegram_backup/DatabaseUpdates.kt
@@ -381,21 +381,30 @@ internal class DB_Update_9(conn: Connection, db: Database) : DatabaseUpdate(conn
 	override fun _doUpdate() {
 		val logger = LoggerFactory.getLogger(DB_Update_9::class.java)
 		println("    Updating supergroup channel message data (this might take some time)...")
-		val rs = stmt.executeQuery("SELECT id, data, source_id FROM messages WHERE source_type='channel' and sender_id IS NULL and api_layer=53")
-		val messages = TLVector<TLAbsMessage>()
-		val messages_to_delete = mutableListOf<Int>()
+		val count = db.queryInt("SELECT COUNT(*) FROM messages WHERE source_type='channel' and sender_id IS NULL and api_layer=53")
+		logger.debug("Found $count candidates for conversion")
+		val limit = 5000
+		var offset = 0
 		var i = 0
-		while (rs.next()) {
-			i++
-			val msg = Database.bytesToTLMessage(rs.getBytes(2))
-			if (msg!!.getFromId() != null) {
-				messages.add(msg)
-				messages_to_delete.add(rs.getInt(1))
+		while (offset + 1 < count) {
+			logger.debug("Querying with limit $limit and offset $offset")
+			val rs = stmt.executeQuery("SELECT id, data, source_id FROM messages WHERE source_type='channel' and sender_id IS NULL and api_layer=53 LIMIT ${limit} OFFSET ${offset}")
+			val messages = TLVector<TLAbsMessage>()
+			val messages_to_delete = mutableListOf<Int>()
+			while (rs.next()) {
+				val msg = Database.bytesToTLMessage(rs.getBytes(2))
+				if (msg!!.getFromId() != null) {
+					i++
+					messages.add(msg)
+					messages_to_delete.add(rs.getInt(1))
+				}
 			}
+			db.saveMessages(messages, api_layer=53, source_type=MessageSource.SUPERGROUP)
+			execute("DELETE FROM messages WHERE id IN (" + messages_to_delete.joinToString() + ")")
+			
+			offset += limit
 		}
-		logger.info("Converted ${messages.size} of ${i} messages.")
-		db.saveMessages(messages, api_layer=53, source_type=MessageSource.SUPERGROUP)
-		execute("DELETE FROM messages WHERE id IN (" + messages_to_delete.joinToString() + ")")
+		logger.info("Converted ${i} of ${count} messages.")
 		println("    Cleaning up the database (this might also take some time, sorry)...")
 		execute("VACUUM")
 	}