[temp file] simplify worker cleanup, add comments to large object functions

src/Gargantext/Core/Worker.hs

@@ -235,10 +235,7 @@ performAction env _state bm = do
       -- TODO CES.filnally
       $(logLocM) DEBUG "[performAction] add to corpus with temporary file"
       CES.finally (addToCorpusWithTempFile _actf_user _actf_cid _actf_args jh)
-          (do
-             let oId = _wtf_file_oid _actf_args
-             $(logLocM) DEBUG $ "[performAction] removing large object: " <> show oId
-             removeLargeObject oId)
+          (removeLargeObject $ _wtf_file_oid _actf_args)
       
     -- | Perform external API search query and index documents in corpus
     AddCorpusWithQuery { .. } -> runWorkerMonad env $ do

src/Gargantext/Database/Prelude.hs

@@ -278,6 +278,12 @@ createDBIfNotExists connStr dbName = do
 -- PostgreSQL Large Object functionality
 -- https://www.postgresql.org/docs/17/largeobjects.html
 
+-- NOTE: During development of this feature, I had problems (in tests)
+-- with a hanging transaction. After debugging, it turned out this
+-- was, for some reason, conflicting with our `logLocM` (though I'm no
+-- sure why). Please be careful when adding debug info to large
+-- objects and if you do, make sure the tests run.
+
 createLargeObject :: BS.ByteString -> DBCmd err PSQL.Oid
 createLargeObject bs = mkCmd $ \c -> PGS.withTransaction c $ do
   oId <- PSQL.loCreat c
@@ -286,6 +292,8 @@ createLargeObject bs = mkCmd $ \c -> PGS.withTransaction c $ do
   PSQL.loClose c loFd
   pure oId
 
+-- | Read a large object directly, given an oid. We read it in a
+-- single transaction, looping by given chunk size
 readLargeObject :: PSQL.Oid -> DBCmd err BS.ByteString
 readLargeObject oId = mkCmd $ \c -> PGS.withTransaction c $ do
   loFd <- PSQL.loOpen c oId PSQL.ReadMode
@@ -303,6 +311,9 @@ readLargeObject oId = mkCmd $ \c -> PGS.withTransaction c $ do
   PSQL.loClose c loFd
   pure s
 
+-- | Read large object by exporting it to a temporary file, then
+-- reading that file. The difference from 'readLargeObject' is that we
+-- have only 1 call inside a transaction
 readLargeObjectViaTempFile :: (CES.MonadMask m, IsDBCmd env err m)
                            => PSQL.Oid -> m BS.ByteString
 readLargeObjectViaTempFile oId = do