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|
{- git-annex general metadata storage log
-
- A line of the log will look like "timestamp field [+-]value [...]"
-
- Note that unset values are preserved. Consider this case:
-
- We have:
-
- 100 foo +x
- 200 foo -x
-
- An unmerged remote has:
-
- 150 foo +x
-
- After union merge, because the foo -x was preserved, we know that
- after the other remote redundantly set foo +x, it was unset,
- and so foo currently has no value.
-
-
- Copyright 2014 Joey Hess <id@joeyh.name>
-
- Licensed under the GNU GPL version 3 or higher.
-}
{-# OPTIONS_GHC -fno-warn-orphans #-}
module Logs.MetaData (
getCurrentMetaData,
addMetaData,
addMetaData',
currentMetaData,
copyMetaData,
) where
import Annex.Common
import Types.MetaData
import Annex.MetaData.StandardFields
import Annex.VectorClock
import qualified Annex.Branch
import qualified Annex
import Logs
import Logs.SingleValue
import Logs.TimeStamp
import qualified Data.Set as S
import qualified Data.Map as M
instance SingleValueSerializable MetaData where
serialize = Types.MetaData.serialize
deserialize = Types.MetaData.deserialize
getMetaDataLog :: Key -> Annex (Log MetaData)
getMetaDataLog key = do
config <- Annex.getGitConfig
readLog $ metaDataLogFile config key
logToCurrentMetaData :: [LogEntry MetaData] -> MetaData
logToCurrentMetaData = currentMetaData . combineMetaData . map value
{- Go through the log from oldest to newest, and combine it all
- into a single MetaData representing the current state.
-
- Automatically generates a lastchanged metadata for each field that's
- currently set, based on timestamps in the log.
-}
getCurrentMetaData :: Key -> Annex MetaData
getCurrentMetaData k = do
ls <- S.toAscList <$> getMetaDataLog k
let loggedmeta = logToCurrentMetaData ls
return $ currentMetaData $ unionMetaData loggedmeta
(lastchanged ls loggedmeta)
where
lastchanged [] _ = emptyMetaData
lastchanged ls (MetaData currentlyset) =
let m = foldl' (flip M.union) M.empty (map genlastchanged ls)
in MetaData $
-- Add a overall lastchanged using the oldest log
-- item (log is in ascending order).
M.insert lastChangedField (lastchangedval $ Prelude.last ls) $
M.mapKeys mkLastChangedField $
-- Only include fields that are currently set.
m `M.intersection` currentlyset
-- Makes each field have the timestamp as its value.
genlastchanged l =
let MetaData m = value l
ts = lastchangedval l
in M.map (const ts) m
lastchangedval l = S.singleton $ toMetaValue $ showts $
case changed l of
VectorClock t -> t
Unknown -> 0
showts = formatPOSIXTime "%F@%H-%M-%S"
{- Adds in some metadata, which can override existing values, or unset
- them, but otherwise leaves any existing metadata as-is. -}
addMetaData :: Key -> MetaData -> Annex ()
addMetaData k metadata = addMetaData' k metadata =<< liftIO currentVectorClock
{- Reusing the same VectorClock when making changes to the metadata
- of multiple keys is a nice optimisation. The same metadata lines
- will tend to be generated across the different log files, and so
- git will be able to pack the data more efficiently. -}
addMetaData' :: Key -> MetaData -> VectorClock -> Annex ()
addMetaData' k d@(MetaData m) c
| d == emptyMetaData = noop
| otherwise = do
config <- Annex.getGitConfig
Annex.Branch.change (metaDataLogFile config k) $
showLog . simplifyLog
. S.insert (LogEntry c metadata)
. parseLog
where
metadata = MetaData $ M.filterWithKey (\f _ -> not (isLastChangedField f)) m
{- Simplify a log, removing historical values that are no longer
- needed.
-
- This is not as simple as just making a single log line with the newest
- state of all metadata. Consider this case:
-
- We have:
-
- 100 foo +x bar +y
- 200 foo -x
-
- An unmerged remote has:
-
- 150 bar -y baz +w
-
- If what we have were simplified to "200 foo -x bar +y" then when the line
- from the remote became available, it would be older than the simplified
- line, and its change to bar would not take effect. That is wrong.
-
- Instead, simplify it to:
-
- 100 bar +y
- 200 foo -x
-
- (Note that this ends up with the same number of lines as the
- unsimplified version, so there's really no point in updating
- the log to this version. Doing so would only add data to git,
- with little benefit.)
-
- Now merging with the remote yields:
-
- 100 bar +y
- 150 bar -y baz +w
- 200 foo -x
-
- Simplifying again:
-
- 150 bar +z baz +w
- 200 foo -x
-}
simplifyLog :: Log MetaData -> Log MetaData
simplifyLog s = case sl of
(newest:rest) ->
let sl' = go [newest] (value newest) rest
in if length sl' < length sl
then S.fromList sl'
else s
_ -> s
where
sl = S.toDescList s
go c _ [] = c
go c newer (l:ls)
| unique == emptyMetaData = go c newer ls
| otherwise = go (l { value = unique } : c)
(unionMetaData unique newer) ls
where
older = value l
unique = older `differenceMetaData` newer
{- Copies the metadata from the old key to the new key.
-
- The exact content of the metadata file is copied, so that the timestamps
- remain the same, and because this is more space-efficient in the git
- repository.
-
- Any metadata already attached to the new key is not preserved.
-
- Returns True when metadata was copied.
-}
copyMetaData :: Key -> Key -> Annex Bool
copyMetaData oldkey newkey
| oldkey == newkey = return False
| otherwise = do
l <- getMetaDataLog oldkey
if logToCurrentMetaData (S.toAscList l) == emptyMetaData
then return False
else do
config <- Annex.getGitConfig
Annex.Branch.change (metaDataLogFile config newkey) $
const $ showLog l
return True
|
