diff --git a/ChangeLog.md b/ChangeLog.md
--- a/ChangeLog.md
+++ b/ChangeLog.md
@@ -1,5 +1,9 @@
 # Changelog for persistent
 
+## 2.9.2
+
+* Add documentation for the `Migration` type and some helpers. [#860](https://github.com/yesodweb/persistent/pull/860)
+
 ## 2.9.1
 
 * Fix [#847](https://github.com/yesodweb/persistent/issues/847): SQL error with `putMany` on Sqlite when Entity has no unique index.
diff --git a/Database/Persist/Class/PersistField.hs b/Database/Persist/Class/PersistField.hs
--- a/Database/Persist/Class/PersistField.hs
+++ b/Database/Persist/Class/PersistField.hs
@@ -190,8 +190,8 @@
     fromPersistValue x = Left $ fromPersistValueError "Int32" "integer" x
 
 instance PersistField Int64 where
-    toPersistValue = PersistInt64 . fromIntegral
-    fromPersistValue (PersistInt64 i)  = Right $ fromIntegral i
+    toPersistValue = PersistInt64
+    fromPersistValue (PersistInt64 i)  = Right i
     fromPersistValue (PersistDouble i) = Right (truncate i :: Int64) -- oracle
     fromPersistValue (PersistByteString bs) = case readInt bs of  -- oracle
                                                Just (i,"") -> Right $ fromIntegral i
diff --git a/Database/Persist/Sql/Migration.hs b/Database/Persist/Sql/Migration.hs
--- a/Database/Persist/Sql/Migration.hs
+++ b/Database/Persist/Sql/Migration.hs
@@ -10,6 +10,11 @@
   , runMigrationSilent
   , runMigrationUnsafe
   , migrate
+  -- * Utilities for constructing migrations
+  , reportErrors
+  , reportError
+  , addMigrations
+  , addMigration
   ) where
 
 
@@ -140,4 +145,37 @@
 migrate allDefs val = do
     conn <- lift $ lift ask
     res <- liftIO $ connMigrateSql conn allDefs (getStmtConn conn) val
-    either tell (lift . tell) res
+    either reportErrors addMigrations res
+
+-- | Report a single error in a 'Migration'.
+--
+-- @since 2.9.2
+reportError :: Text -> Migration
+reportError = tell . pure
+
+-- | Report multiple errors in a 'Migration'.
+--
+-- @since 2.9.2
+reportErrors :: [Text] -> Migration
+reportErrors = tell
+
+-- | Add a migration to the migration plan.
+--
+-- @since 2.9.2
+addMigration
+    :: Bool
+    -- ^ Is the migration safe to run? (eg a non-destructive and idempotent
+    -- update on the schema)
+    -> Sql
+    -- ^ A 'Text' value representing the command to run on the database.
+    -> Migration
+addMigration isSafe sql = lift (tell [(isSafe, sql)])
+
+-- | Add a 'CautiousMigration' (aka a @[('Bool', 'Text')]@) to the
+-- migration plan.
+--
+-- @since 2.9.2
+addMigrations
+    :: CautiousMigration
+    -> Migration
+addMigrations = lift . tell
diff --git a/Database/Persist/Sql/Orphan/PersistStore.hs b/Database/Persist/Sql/Orphan/PersistStore.hs
--- a/Database/Persist/Sql/Orphan/PersistStore.hs
+++ b/Database/Persist/Sql/Orphan/PersistStore.hs
@@ -26,7 +26,7 @@
 import Database.Persist.Sql.Util (
     dbIdColumns, keyAndEntityColumnNames, parseEntityValues, entityColumnNames
   , updatePersistValue, mkUpdateText, commaSeparated)
-import           Data.Conduit (ConduitM, (=$=), (.|), runConduit)
+import           Data.Conduit (ConduitM, (.|), runConduit)
 import qualified Data.Conduit.List as CL
 import qualified Data.Text as T
 import Data.Text (Text, unpack)
@@ -335,7 +335,7 @@
                     Left s -> liftIO $ throwIO $ PersistMarshalError s
                     Right row -> return row
         withRawQuery sql (Foldable.foldMap keyToValues ks) $ do
-            es <- CL.mapM parse =$= CL.consume
+            es <- CL.mapM parse .| CL.consume
             return $ Map.fromList $ fmap (\e -> (entityKey e, entityVal e)) es
 
 instance PersistStoreRead SqlReadBackend where
diff --git a/Database/Persist/Sql/Types.hs b/Database/Persist/Sql/Types.hs
--- a/Database/Persist/Sql/Types.hs
+++ b/Database/Persist/Sql/Types.hs
@@ -60,6 +60,14 @@
 -- Bool indicates if the Sql is safe
 type CautiousMigration = [(Bool, Sql)]
 
+-- | A 'Migration' is a four level monad stack consisting of:
+--
+-- * @'WriterT' ['Text']@ representing a log of errors in the migrations.
+-- * @'WriterT' 'CautiousMigration'@ representing a list of migrations to
+--   run, along with whether or not they are safe.
+-- * @'ReaderT' 'SqlBackend'@, aka the 'SqlPersistT' transformer for
+--   database interop.
+-- * @'IO'@ for arbitrary IO.
 type Migration = WriterT [Text] (WriterT CautiousMigration (ReaderT SqlBackend IO)) ()
 
 type ConnectionPool = Pool SqlBackend
diff --git a/persistent.cabal b/persistent.cabal
--- a/persistent.cabal
+++ b/persistent.cabal
@@ -1,5 +1,5 @@
 name:            persistent
-version:         2.9.1
+version:         2.9.2
 license:         MIT
 license-file:    LICENSE
 author:          Michael Snoyman <michael@snoyman.com>
@@ -22,7 +22,7 @@
     if flag(nooverlap)
         cpp-options: -DNO_OVERLAP
 
-    build-depends:   base                     >= 4.7       && < 5
+    build-depends:   base                     >= 4.8       && < 5
                    , bytestring               >= 0.9
                    , transformers             >= 0.2.1
                    , time                     >= 1.1.4