fix(slack): swapped checkpoint index

backend/onyx/connectors/slack/connector.py

@@ -761,7 +761,7 @@ def _load_from_checkpoint(
         Step 2: Loop through each channel. For each channel:
             Step 2.1: Get messages within the time range.
             Step 2.2: Process messages in parallel, yield back docs.
-            Step 2.3: Update checkpoint with new_latest, seen_thread_ts, and current_channel.
+            Step 2.3: Update checkpoint with new_oldest, seen_thread_ts, and current_channel.
                       Slack returns messages from newest to oldest, so we need to keep track of
                       the latest message we've seen in each channel.
             Step 2.4: If there are no more messages in the channel, switch the current
@@ -837,7 +837,8 @@ def _load_from_checkpoint(
 
             channel_message_ts = checkpoint.channel_completion_map.get(channel_id)
             if channel_message_ts:
-                latest = channel_message_ts
+                # Set oldest to the checkpoint timestamp to resume from where we left off
+                oldest = channel_message_ts
 
             logger.debug(
                 f"Getting messages for channel {channel} within range {oldest} - {latest}"
@@ -855,7 +856,8 @@ def _load_from_checkpoint(
                 f"{latest=}"
             )
 
-            new_latest = message_batch[-1]["ts"] if message_batch else latest
+            # message_batch[0] is the newest message (Slack returns newest to oldest)
+            new_oldest = message_batch[0]["ts"] if message_batch else latest
 
             num_threads_start = len(seen_thread_ts)
 
@@ -906,15 +908,14 @@ def _load_from_checkpoint(
             num_threads_processed = len(seen_thread_ts) - num_threads_start
 
             # calculate a percentage progress for the current channel by determining
-            # our viable range start and end, and the latest timestamp we are querying
-            # up to
-            new_latest_seconds_epoch = SecondsSinceUnixEpoch(new_latest)
-            if new_latest_seconds_epoch > end:
+            # how much of the time range we've processed so far
+            new_oldest_seconds_epoch = SecondsSinceUnixEpoch(new_oldest)
+            range_start = start if start else max(0, channel_created)
+            if new_oldest_seconds_epoch < range_start:
                 range_complete = 0.0
             else:
-                range_complete = end - new_latest_seconds_epoch
+                range_complete = new_oldest_seconds_epoch - range_start
 
-            range_start = max(0, channel_created)
             range_total = end - range_start
             if range_total <= 0:
                 range_total = 1
@@ -935,7 +936,7 @@ def _load_from_checkpoint(
             )
 
             checkpoint.seen_thread_ts = list(seen_thread_ts)
-            checkpoint.channel_completion_map[channel["id"]] = new_latest
+            checkpoint.channel_completion_map[channel["id"]] = new_oldest
 
             # bypass channels where the first set of messages seen are all bots
             # check at least MIN_BOT_MESSAGE_THRESHOLD messages are in the batch