Remove old message duplicate code

- Calculating so many hashes for each Message is quite expensive
- It hides our own implementation bugs, like when we retrieve history
from a MUC with wrong timestamps, or on rejoin. We never know about it
because the Messages are dropped.
- It should not be necessary anymore. The original problem was a bug
in nbxmpp which triggered mass resending of old messages.

gajim/common/connection_handlers.py

@@ -725,8 +725,6 @@ class ConnectionHandlersBase:
         # IDs of sent messages (https://trac.gajim.org/ticket/8222)
         self.sent_message_ids = []
 
-        self.received_message_hashes = []
-
         # We decrypt GPG messages one after the other. Keep queue in mem
         self.gpg_messages_to_decrypt = []
 
@@ -2048,8 +2046,6 @@ ConnectionHandlersBase, ConnectionJingle, ConnectionIBBytestream):
         app.nec.push_incoming_event(SignedInEvent(None, conn=self))
         self.send_awaiting_pep()
         self.continue_connect_info = None
-        # hashes of already received messages
-        self.received_message_hashes = []
 
     def _SearchCB(self, con, iq_obj):
         log.debug('SearchCB')

gajim/common/connection_handlers_events.py

@@ -1472,22 +1472,6 @@ class DecryptedMessageReceivedEvent(nec.NetworkIncomingEvent, HelperEvent):
         if replace:
             self.correct_id = replace.getAttr('id')
 
-        # ignore message duplicates
-        if self.msgtxt and self.id_ and self.jid:
-            self.msghash = hashlib.sha256(("%s|%s|%s" % (
-                hashlib.sha256(self.msgtxt.encode('utf-8')).hexdigest(),
-                hashlib.sha256(self.id_.encode('utf-8')).hexdigest(),
-                hashlib.sha256(self.jid.encode('utf-8')).hexdigest())).encode(
-                'utf-8')).digest()
-            if self.msghash in self.conn.received_message_hashes:
-                log.info("Ignoring duplicated message from '%s' with id '%s'" % (self.jid, self.id_))
-                return False
-            else:
-                log.debug("subhashes: msgtxt, id_, jid = ('%s', '%s', '%s')" % (hashlib.sha256(self.msgtxt.encode('utf-8')).hexdigest(), hashlib.sha256(self.id_.encode('utf-8')).hexdigest(), hashlib.sha256(self.jid.encode('utf-8')).hexdigest()))
-                self.conn.received_message_hashes.append(self.msghash)
-                # only record the last 20000 hashes (should be about 1MB [32 bytes per hash]
-                # and about 24 hours if you receive a message every 5 seconds)
-                self.conn.received_message_hashes = self.conn.received_message_hashes[-20000:]
         return True
 
 class ChatstateReceivedEvent(nec.NetworkIncomingEvent):