From b873f05ca7e86344a28d269d682b7ffd8a88baca Mon Sep 17 00:00:00 2001
From: Joey Hess <joey@kitenet.net>
Date: Thu, 10 Jul 2014 17:06:04 -0400
Subject: migrate: Avoid re-checksumming when migrating from hashE to hash
 backend.

---
 Backend/Hash.hs | 10 ++++++++++
 Backend/URL.hs  |  1 +
 Backend/WORM.hs |  1 +
 3 files changed, 12 insertions(+)

(limited to 'Backend')

diff --git a/Backend/Hash.hs b/Backend/Hash.hs
index 41368a5bb..3ff496271 100644
--- a/Backend/Hash.hs
+++ b/Backend/Hash.hs
@@ -44,6 +44,7 @@ genBackend hash = Just Backend
 	, getKey = keyValue hash
 	, fsckKey = Just $ checkKeyChecksum hash
 	, canUpgradeKey = Just needsUpgrade
+	, fastMigrate = Just trivialMigrate
 	}
 
 genBackendE :: Hash -> Maybe Backend
@@ -129,6 +130,15 @@ needsUpgrade :: Key -> Bool
 needsUpgrade key = "\\" `isPrefixOf` keyHash key ||
 	any (not . validExtension) (takeExtensions $ keyName key)
 
+{- Fast migration from hashE to hash backend. (Optimisation) -}
+trivialMigrate :: Key -> Backend -> Maybe Key
+trivialMigrate oldkey newbackend
+	| keyBackendName oldkey == name newbackend ++ "E" = Just $ oldkey
+		{ keyName = keyHash oldkey
+		, keyBackendName = name newbackend
+		}
+	| otherwise = Nothing
+
 hashFile :: Hash -> FilePath -> Integer -> Annex String
 hashFile hash file filesize = liftIO $ go hash
   where
diff --git a/Backend/URL.hs b/Backend/URL.hs
index a8161c98d..4233c56bc 100644
--- a/Backend/URL.hs
+++ b/Backend/URL.hs
@@ -24,6 +24,7 @@ backend = Backend
 	, getKey = const $ return Nothing
 	, fsckKey = Nothing
 	, canUpgradeKey = Nothing
+	, fastMigrate = Nothing
 	}
 
 {- Every unique url has a corresponding key. -}
diff --git a/Backend/WORM.hs b/Backend/WORM.hs
index 60db42f56..cc7123850 100644
--- a/Backend/WORM.hs
+++ b/Backend/WORM.hs
@@ -22,6 +22,7 @@ backend = Backend
 	, getKey = keyValue
 	, fsckKey = Nothing
 	, canUpgradeKey = Nothing
+	, fastMigrate = Nothing
 	}
 
 {- The key includes the file size, modification time, and the
-- 
cgit v1.2.3