git-annex/Backend/URL.hs
Joey Hess 81d402216d cache the serialization of a Key
This will speed up the common case where a Key is deserialized from
disk, but is then serialized to build eg, the path to the annex object.

Previously attempted in 4536c93bb2
and reverted in 96aba8eff7.
The problems mentioned in the latter commit are addressed now:

Read/Show of KeyData is backwards-compatible with Read/Show of Key from before
this change, so Types.Distribution will keep working.

The Eq instance is fixed.

Also, Key has smart constructors, avoiding needing to remember to update
the cached serialization.

Used git-annex benchmark:
  find is 7% faster
  whereis is 3% faster
  get when all files are already present is 5% faster
Generally, the benchmarks are running 0.1 seconds faster per 2000 files,
on a ram disk in my laptop.
2019-11-22 17:49:16 -04:00

39 lines
851 B
Haskell

{- git-annex "URL" backend -- keys whose content is available from urls.
-
- Copyright 2011 Joey Hess <id@joeyh.name>
-
- Licensed under the GNU AGPL version 3 or higher.
-}
module Backend.URL (
backends,
fromUrl
) where
import Annex.Common
import Types.Key
import Types.Backend
import Backend.Utilities
backends :: [Backend]
backends = [backend]
backend :: Backend
backend = Backend
{ backendVariety = URLKey
, getKey = \_ _ -> return Nothing
, verifyKeyContent = Nothing
, canUpgradeKey = Nothing
, fastMigrate = Nothing
-- The content of an url can change at any time, so URL keys are
-- not stable.
, isStableKey = const False
}
{- Every unique url has a corresponding key. -}
fromUrl :: String -> Maybe Integer -> Key
fromUrl url size = mkKey $ \k -> k
{ keyName = genKeyName url
, keyVariety = URLKey
, keySize = size
}