Do not write snapshot if it exists

Author: jasagredo

ouroboros-consensus/src/ouroboros-consensus/Ouroboros/Consensus/Storage/LedgerDB/V2/LSM.hs

@@ -76,6 +76,7 @@ import Data.Void
 import Database.LSMTree (Session, Table)
 import qualified Database.LSMTree as LSM
 import qualified Database.LSMTree.Internal.Types as LSM
+-- import qualified Debug.Trace as Debug
 import GHC.Generics
 import NoThunks.Class
 import Ouroboros.Consensus.Block
@@ -191,7 +192,9 @@ newLSMLedgerTablesHandle tracer rr session (resKey, t0) = do
       , takeHandleSnapshot = \_ snapshotName -> do
           guardClosed tv $
             \table -> do
-              Monad.void $ LSM.saveSnapshot (fromString snapshotName) "UTxO table" table
+              exists <- LSM.doesSnapshotExist session (fromString snapshotName)
+              -- Debug.traceShowM =<< LSM.listSnapshots session
+              Monad.when (not exists) $ LSM.saveSnapshot (fromString snapshotName) "UTxO table" table
               pure Nothing
       , tablesSize = pure Nothing
       }