Structure, refactor and clean up trace messages

We give the trace message datatypes more structure (see the `$traces` Haddock
section), and we add few new messages. In the process, we apply some minor
refactorings to tracer calls and surrounding code.

Author: jorisdral

src/Database/LSMTree.hs

@@ -185,11 +185,13 @@ module Database.LSMTree (
   -- * Traces #traces#
   Tracer,
   LSMTreeTrace (..),
+  SessionTrace (..),
   TableTrace (..),
   CursorTrace (..),
   MergeTrace (..),
-  CursorId (..),
+  SessionId (..),
   TableId (..),
+  CursorId (..),
   AtLevel (..),
   LevelNo (..),
   NumEntries (..),
@@ -262,7 +264,8 @@ import           Database.LSMTree.Internal.Unsafe (BlobRefInvalidError (..),
                      ResolveSerialisedValue, SessionClosedError (..),
                      SessionDirCorruptedError (..),
                      SessionDirDoesNotExistError (..),
-                     SessionDirLockedError (..), SnapshotCorruptedError (..),
+                     SessionDirLockedError (..), SessionId (..),
+                     SessionTrace (..), SnapshotCorruptedError (..),
                      SnapshotDoesNotExistError (..), SnapshotExistsError (..),
                      SnapshotNotCompatibleError (..), TableClosedError (..),
                      TableCorruptedError (..), TableTooLargeError (..),

src/Database/LSMTree/Internal/RunReader.hs

@@ -90,6 +90,7 @@ data RunReader m h = RunReader {
     }
 
 data OffsetKey = NoOffsetKey | OffsetKey !SerialisedKey
+  deriving stock Show
 
 {-# SPECIALISE new ::
      OffsetKey

src/Database/LSMTree/Internal/UniqCounter.hs

@@ -11,6 +11,7 @@ module Database.LSMTree.Internal.UniqCounter (
   uniqueToCursorId,
 ) where
 
+import           Control.DeepSeq (NFData (..))
 import           Control.Monad.Primitive (PrimMonad, PrimState)
 import           Data.Primitive.PrimVar as P
 import           Database.LSMTree.Internal.RunNumber
@@ -35,6 +36,9 @@ uniqueToCursorId (Unique n) = CursorId n
 --
 newtype UniqCounter m = UniqCounter (PrimVar (PrimState m) Int)
 
+instance NFData (UniqCounter m) where
+  rnf (UniqCounter (P.PrimVar mba)) = rnf mba
+
 {-# INLINE newUniqCounter #-}
 newUniqCounter :: PrimMonad m => Int -> m (UniqCounter m)
 newUniqCounter = fmap UniqCounter . P.newPrimVar