git-annex/Database/Init.hs

{- Persistent sqlite database initialization
 -
 - Copyright 2015-2020 Joey Hess <id@joeyh.name>
 -
 - Licensed under the GNU AGPL version 3 or higher.
 -}

{-# LANGUAGE OverloadedStrings #-}

module Database.Init where

import Annex.Common
import Annex.Perms
import Utility.FileMode
import qualified Utility.RawFilePath as R

import Database.Persist.Sqlite
import Lens.Micro
import qualified Data.Text as T
import qualified System.FilePath.ByteString as P

{- Ensures that the database is freshly initialized. Deletes any
 - existing database. Pass the migration action for the database.
 -
 - The permissions of the database are set based on the
 - core.sharedRepository setting. Setting these permissions on the main db
 - file causes Sqlite to always use the same permissions for additional
 - files it writes later on
 -}
initDb :: P.RawFilePath -> SqlPersistM () -> Annex ()
initDb db migration = do
	let dbdir = P.takeDirectory db
	let tmpdbdir = dbdir <> ".tmp"
	let tmpdb = tmpdbdir P.</> "db"
	let tdb = T.pack (fromRawFilePath tmpdb)
	createAnnexDirectory tmpdbdir
	liftIO $ runSqliteInfo (enableWAL tdb) migration
	setAnnexDirPerm tmpdbdir
	-- Work around sqlite bug that prevents it from honoring
	-- less restrictive umasks.
	liftIO $ R.setFileMode tmpdb =<< defaultFileMode
	setAnnexFilePerm tmpdb
	liftIO $ do
		void $ tryIO $ removeDirectoryRecursive (fromRawFilePath dbdir)
		R.rename tmpdbdir dbdir

{- Make sure that the database uses WAL mode, to prevent readers
 - from blocking writers, and prevent a writer from blocking readers.
 -
 - This is the default in recent persistent-sqlite versions, but 
 - force it on just in case. 
 -
 - Note that once WAL mode is enabled, it will persist whenever the
 - database is opened. -}
enableWAL :: T.Text -> SqliteConnectionInfo
enableWAL db = over walEnabled (const True) $ 
	mkSqliteConnectionInfo db