diff --git a/chan-delorean.cabal b/chan-delorean.cabal
index 1b0a10f..0eb0ef9 100644
--- a/chan-delorean.cabal
+++ b/chan-delorean.cabal
@@ -67,7 +67,6 @@ executable chan-delorean
     -- Modules included in this executable, other than Main.
     other-modules:
                       JSONParsing
-                      DataClient
                       JSONSettings
                       SitesType
                       BoardsType
@@ -79,6 +78,8 @@ executable chan-delorean
                       Common.Network.HttpClient
                       Hash
                       Data.WordUtil
+                      Network.DataClient
+                      Network.DataClientTypes
 
     -- LANGUAGE extensions used by modules in this package.
     -- other-extensions:
diff --git a/sql/initialize.sql b/sql/initialize.sql
index 7d1c40f..1dd865f 100644
--- a/sql/initialize.sql
+++ b/sql/initialize.sql
@@ -381,7 +381,8 @@ GRANT EXECUTE ON FUNCTION get_posts         TO chan_archive_anon;
 -- GRANT usage, select ON SEQUENCE boards_board_id_seq TO chan_archive_anon;
 GRANT chan_archive_anon                 TO admin;
 
-CREATE ROLE chan_archiver noinherit login password 'test_password';
+CREATE ROLE chan_archiver noinherit login password 'test_password'
+    SET pgrst.db_aggregates_enabled = 'true';
 GRANT CONNECT ON DATABASE chan_archives TO chan_archiver;
 GRANT chan_archive_anon                 TO chan_archiver;
 GRANT ALL ON sites                      TO chan_archiver;
diff --git a/src/Backfill.hs b/src/Backfill.hs
index bb57ebb..5b8d267 100644
--- a/src/Backfill.hs
+++ b/src/Backfill.hs
@@ -36,7 +36,7 @@ import JSONParsing
 import JSONSettings
 import qualified JSONCommonTypes as JS
 import qualified JSONPost   as JSONPosts
-import qualified DataClient as Client
+import qualified Network.DataClient as Client
 import qualified SitesType  as Sites
 import qualified BoardsType as Boards
 import qualified ThreadType as Threads
@@ -45,6 +45,8 @@ import qualified Common.PostsType as Posts
 import qualified Hash as Hash
 import qualified Data.WordUtil as Words
 
+import Debug.Trace (trace, traceShowId)
+
 newtype SettingsCLI = SettingsCLI
   { jsonFile :: FilePath
   } deriving (Show, Data, Typeable)
@@ -202,7 +204,11 @@ readPosts settings board thread = do
 
 
 apiPostToPostKey :: Threads.Thread -> JSONPosts.Post -> Client.PostId
-apiPostToPostKey thread post = Client.PostId (Threads.thread_id thread) (JSONPosts.no post)
+apiPostToPostKey thread post =
+    Client.PostId
+        { Client.thread_id = (Threads.thread_id thread)
+        , Client.board_post_id = (JSONPosts.no post)
+        }
 
 -- Convert Post to DbPost
 apiPostToArchivePost :: Int -> Threads.Thread -> JSONPosts.Post -> Posts.Post
@@ -531,18 +537,20 @@ createNewPosts
     -> [ (Threads.Thread, JSONPosts.Post, Client.PostId) ]
     -> IO [ Posts.Post ]
 createNewPosts settings tuples = do
-    existing_post_results <- Client.getPosts settings (map (\(_, _, c) -> c) tuples)
+    existing_post_results <- Client.getPosts settings $ map (\(_, _, c) -> c) tuples
     existing_posts <- either handleError return existing_post_results
 
+    thread_max_local_idx_result <- Client.getThreadMaxLocalIdx settings thread_ids
+    thread_max_local_idxs <- either handleError return thread_max_local_idx_result
+
     let existing_set :: Set (Int64, Int64) = Set.fromList (map (\x -> (Posts.thread_id x, Posts.board_post_id x)) existing_posts)
 
     let to_insert_list :: [ (Threads.Thread, JSONPosts.Post, Client.PostId) ] =
             sortBy (comparing $ \(_, _, p) -> Client.board_post_id p) $
-                determineNew tuples existing_set
+                newPosts tuples existing_set
 
     -- Map of thread_id to the largest local_idx value (which would be the number of the last post in the thread)
-    let local_idx :: Map.Map Int64 Int = foldr (Map.unionWith max) Map.empty $
-            map (\x -> Map.singleton (Posts.thread_id x) (Posts.local_idx x)) existing_posts
+    let local_idx :: Map.Map Int64 Int = Map.fromList thread_max_local_idxs
 
     let insert_posts = fst $ foldl' foldFn ([], local_idx) to_insert_list
 
@@ -555,6 +563,7 @@ createNewPosts settings tuples = do
     --      - need to compare posts already in the map with another post and keep the max local_idx ✓
     -- to get the new local_idx, we must order the to_insert_list by board_post_id, and look up each entry ✓
 
+    print insert_posts
     posts_result <- Client.postPosts settings insert_posts
     new_posts <- either handleError return posts_result
     return $ existing_posts ++ new_posts
@@ -562,14 +571,17 @@ createNewPosts settings tuples = do
     where
         handleError err = print err >> exitFailure
 
-        determineNew :: [(Threads.Thread, JSONPosts.Post, Client.PostId)] -> Set (Int64, Int64) -> [(Threads.Thread, JSONPosts.Post, Client.PostId)]
-        determineNew ts existing_set = filter (\(_, _, c) -> Set.notMember (Client.thread_id c, Client.board_post_id c) existing_set) ts
+        thread_ids :: [ Int64 ]
+        thread_ids = Set.elems $ Set.fromList $ map (\(t, _, _) -> Threads.thread_id t) tuples
+
+        newPosts :: [(Threads.Thread, JSONPosts.Post, Client.PostId)] -> Set (Int64, Int64) -> [(Threads.Thread, JSONPosts.Post, Client.PostId)]
+        newPosts ts existing_set = filter (\(_, _, c) -> Set.notMember (Client.thread_id c, Client.board_post_id c) existing_set) ts
 
         foldFn :: ([Posts.Post], Map.Map Int64 Int) -> (Threads.Thread, JSONPosts.Post, Client.PostId) -> ([Posts.Post], Map.Map Int64 Int)
-        foldFn (posts, idx_map) (t, p, c) =
-            case Map.lookup thread_id idx_map of
-                Nothing -> ((post 1) : posts, Map.insert thread_id 1 idx_map)
-                Just i -> ((post (i + 1)) : posts, Map.insert thread_id (i + 1) idx_map)
+        foldFn (posts, idx_map) (t, p, c) = trace "foldFn" $
+            case Map.lookup thread_id (trace ("map size: " ++ (show $ length idx_map)) idx_map) of
+                Nothing -> (traceShowId (post 1) : posts, trace ("inserting_1 " ++ show thread_id ++ ": 1")$ Map.insert thread_id 1 idx_map)
+                Just i -> (traceShowId (post (i + 1)) : posts, trace ("inserting_2 " ++ show thread_id ++ ": " ++ show (i + 1)) $ Map.insert thread_id (i + 1) idx_map)
 
             where
                 post :: Int -> Posts.Post
@@ -666,4 +678,6 @@ main = do
             Nothing -> do
                 putStrLn "Error: Invalid JSON format."
                 exitFailure
-            Just settings -> processBackupDirectory settings
+            Just settings -> do
+                processBackupDirectory settings
+                putStrLn "Done!"
diff --git a/src/Common b/src/Common
index aed106f..ffe952e 160000
--- a/src/Common
+++ b/src/Common
@@ -1 +1 @@
-Subproject commit aed106f40e24125d9057d3a9dda934a41c6d68a0
+Subproject commit ffe952e22939b21f8576d79752c863a95c208e1e
diff --git a/src/DataClient.hs b/src/Network/DataClient.hs
similarity index 88%
rename from src/DataClient.hs
rename to src/Network/DataClient.hs
index be013fe..4a1d32b 100644
--- a/src/DataClient.hs
+++ b/src/Network/DataClient.hs
@@ -1,7 +1,7 @@
 {-# LANGUAGE OverloadedStrings #-}
 {-# LANGUAGE DeriveAnyClass #-}
 
-module DataClient
+module Network.DataClient
   ( HttpError(..)
   , PostId (..)
   , get
@@ -11,6 +11,7 @@ module DataClient
   , post
   , postBoards
   , getThreads
+  , getThreadMaxLocalIdx
   , postThreads
   , getPosts
   , postPosts
@@ -43,14 +44,14 @@ import qualified ThreadType as Threads
 import qualified Common.AttachmentType as Attachments
 import qualified Common.PostsType  as Posts
 import Common.Network.HttpClient
+import qualified Network.DataClientTypes as T
 
 
 data PostId = PostId
-    { board_post_id :: Int64
-    , thread_id     :: Int64
+    { thread_id     :: Int64
+    , board_post_id :: Int64
     } deriving (Show, Generic, ToJSON)
 
-
 getSiteBoards :: T.JSONSettings -> Int -> IO (Either HttpError [ Boards.Board ])
 getSiteBoards settings site_id_ = get settings path >>= return . eitherDecodeResponse
   where
@@ -116,6 +117,19 @@ getThreads settings board_id board_thread_ids =
         ids :: String = intercalate "," $ map show board_thread_ids
 
 
+getThreadMaxLocalIdx :: T.JSONSettings -> [ Int64 ] -> IO (Either HttpError [(Int64, Int)])
+getThreadMaxLocalIdx settings thread_ids = do
+    result :: Either HttpError [ T.ThreadMaxIdx ] <- get settings path >>= return . eitherDecodeResponse
+
+    let results = result >>= \x -> return $ map (\t -> (T.thread_id t, T.max_idx t)) x
+
+    return results
+
+    where
+        path = "/posts?select=thread_id,max_idx:local_idx.max()&thread_id=in.(" ++ ids ++ ")"
+        ids :: String = intercalate "," $ map show thread_ids
+
+
 -- | Splits a list into chunks of a given size.
 chunkList :: Int -> [a] -> [[a]]
 chunkList _ [] = []
@@ -172,6 +186,7 @@ getPosts :: T.JSONSettings -> [ PostId ] -> IO (Either HttpError [Posts.Post])
 getPosts settings xs = do
     results <- forM (chunkList chunkSize xs) (getPostsChunk settings)
     return $ combineResults results
+
   where
     chunkSize = 1000
 
@@ -180,7 +195,7 @@ postPosts
     :: T.JSONSettings
     -> [ Posts.Post ]
     -> IO (Either HttpError [ Posts.Post ])
-postPosts settings posts = do
+postPosts settings posts =
     post settings "/posts" payload True >>= return . eitherDecodeResponse
 
     where
diff --git a/src/Network/DataClientTypes.hs b/src/Network/DataClientTypes.hs
new file mode 100644
index 0000000..c74d0e2
--- /dev/null
+++ b/src/Network/DataClientTypes.hs
@@ -0,0 +1,13 @@
+{-# LANGUAGE DeriveAnyClass #-}
+
+module Network.DataClientTypes where
+
+import Data.Int (Int64)
+import Data.Aeson (FromJSON)
+import GHC.Generics
+
+data ThreadMaxIdx = ThreadMaxIdx
+    { thread_id :: Int64
+    , max_idx   :: Int
+    } deriving (Show, Generic, FromJSON)
+