add database benchmark

The benchmark shows that the database access is quite fast indeed!
And, it scales linearly to the number of keys, with one exception,
getAssociatedKey.

Based on this benchmark, I don't think I need worry about optimising
for cases where all files are locked and the database is mostly empty.
In those cases, database access will be misses, and according to this
benchmark, should add only 50 milliseconds to runtime.

(NB: There may be some overhead to getting the database opened and locking
the handle that this benchmark doesn't see.)

joey@darkstar:~/src/git-annex>./git-annex benchmark
setting up database with 1000
setting up database with 10000
benchmarking keys database/getAssociatedFiles from 1000 (hit)
time                 62.77 μs   (62.70 μs .. 62.85 μs)
                     1.000 R²   (1.000 R² .. 1.000 R²)
mean                 62.81 μs   (62.76 μs .. 62.88 μs)
std dev              201.6 ns   (157.5 ns .. 259.5 ns)

benchmarking keys database/getAssociatedFiles from 1000 (miss)
time                 50.02 μs   (49.97 μs .. 50.07 μs)
                     1.000 R²   (1.000 R² .. 1.000 R²)
mean                 50.09 μs   (50.04 μs .. 50.17 μs)
std dev              206.7 ns   (133.8 ns .. 295.3 ns)

benchmarking keys database/getAssociatedKey from 1000 (hit)
time                 211.2 μs   (210.5 μs .. 212.3 μs)
                     1.000 R²   (0.999 R² .. 1.000 R²)
mean                 211.0 μs   (210.7 μs .. 212.0 μs)
std dev              1.685 μs   (334.4 ns .. 3.517 μs)

benchmarking keys database/getAssociatedKey from 1000 (miss)
time                 173.5 μs   (172.7 μs .. 174.2 μs)
                     1.000 R²   (0.999 R² .. 1.000 R²)
mean                 173.7 μs   (173.0 μs .. 175.5 μs)
std dev              3.833 μs   (1.858 μs .. 6.617 μs)
variance introduced by outliers: 16% (moderately inflated)

benchmarking keys database/getAssociatedFiles from 10000 (hit)
time                 64.01 μs   (63.84 μs .. 64.18 μs)
                     1.000 R²   (1.000 R² .. 1.000 R²)
mean                 64.85 μs   (64.34 μs .. 66.02 μs)
std dev              2.433 μs   (547.6 ns .. 4.652 μs)
variance introduced by outliers: 40% (moderately inflated)

benchmarking keys database/getAssociatedFiles from 10000 (miss)
time                 50.33 μs   (50.28 μs .. 50.39 μs)
                     1.000 R²   (1.000 R² .. 1.000 R²)
mean                 50.32 μs   (50.26 μs .. 50.38 μs)
std dev              202.7 ns   (167.6 ns .. 252.0 ns)

benchmarking keys database/getAssociatedKey from 10000 (hit)
time                 1.142 ms   (1.139 ms .. 1.146 ms)
                     1.000 R²   (1.000 R² .. 1.000 R²)
mean                 1.142 ms   (1.140 ms .. 1.144 ms)
std dev              7.142 μs   (4.994 μs .. 10.98 μs)

benchmarking keys database/getAssociatedKey from 10000 (miss)
time                 1.094 ms   (1.092 ms .. 1.096 ms)
                     1.000 R²   (1.000 R² .. 1.000 R²)
mean                 1.095 ms   (1.095 ms .. 1.097 ms)
std dev              4.277 μs   (2.591 μs .. 7.228 μs)

8 files changed, 135 insertions, 12 deletions

diff --git a/CmdLine/GitAnnex.hs b/CmdLine/GitAnnex.hs
index ba7689f70..0383dada3 100644
--- a/CmdLine/GitAnnex.hs
+++ b/CmdLine/GitAnnex.hs
@@ -115,6 +115,9 @@ import qualified Command.Test
 import qualified Command.FuzzTest
 import qualified Command.TestRemote
 #endif
+#ifdef WITH_BENCHMARK
+import qualified Command.Benchmark
+#endif
 #ifdef WITH_EKG
 import System.Remote.Monitoring
 #endif
@@ -221,6 +224,9 @@ cmds testoptparser testrunner =
 	, Command.FuzzTest.cmd
 	, Command.TestRemote.cmd
 #endif
+#ifdef WITH_BENCHMARK
+	, Command.Benchmark.cmd
+#endif
 	]
 
 run :: Parser TestOptions -> Maybe TestRunner -> [String] -> IO ()
diff --git a/Command/Benchmark.hs b/Command/Benchmark.hs
new file mode 100644
index 000000000..d4585fdb8
--- /dev/null
+++ b/Command/Benchmark.hs
@@ -0,0 +1,106 @@
+{- git-annex benchmark
+ -
+ - Copyright 2016 Joey Hess <id@joeyh.name>
+ -
+ - Licensed under the GNU GPL version 3 or higher.
+ -}
+
+{-# OPTIONS_GHC -fno-warn-orphans #-}
+
+module Command.Benchmark where
+
+import Command
+import Database.Types
+import qualified Database.Keys.SQL as SQL
+import qualified Database.Queue as H
+import Utility.Tmp
+import Git.FilePath
+
+import Criterion.Main
+import Criterion.Internal (runAndAnalyse)
+import Criterion.Monad
+import Control.Monad.IO.Class (liftIO)
+import Control.Monad
+import Control.DeepSeq
+import System.FilePath
+import System.Random
+
+cmd :: Command
+cmd = noRepo (withParams benchmark) $
+	dontCheck repoExists $
+		command "benchmark" SectionTesting
+			"run benchmarks"
+			paramNothing
+			(withParams (liftIO . benchmark))
+
+benchmark :: CmdParams -> IO ()
+benchmark _ = withTmpDirIn "." "benchmark" $ \tmpdir -> do
+	-- benchmark different sizes of databases
+	dbs <- mapM (benchDb tmpdir)
+		[ 1000
+		, 10000
+		-- , 100000
+		]
+	-- can't use Criterion's defaultMain here because it looks at
+	-- command-line parameters
+	withConfig defaultConfig $ runAndAnalyse (const True) $
+		bgroup "keys database" $ flip concatMap dbs $ \db ->
+			[ getAssociatedFilesHitBench db
+			, getAssociatedFilesMissBench db
+			, getAssociatedKeyHitBench db
+			, getAssociatedKeyMissBench db
+			]
+
+getAssociatedFilesHitBench :: BenchDb -> Benchmark
+getAssociatedFilesHitBench ( BenchDb h num) = bench ("getAssociatedFiles from " ++ show num ++ " (hit)") $ nfIO $ do
+	n <- getStdRandom (randomR (1,num))
+	SQL.getAssociatedFiles (keyN n) (SQL.ReadHandle h)
+
+getAssociatedFilesMissBench :: BenchDb -> Benchmark
+getAssociatedFilesMissBench ( BenchDb h num) = bench ("getAssociatedFiles from " ++ show num ++ " (miss)") $ nfIO $
+	SQL.getAssociatedFiles keyMiss (SQL.ReadHandle h)
+
+getAssociatedKeyHitBench :: BenchDb -> Benchmark
+getAssociatedKeyHitBench (BenchDb h num) = bench ("getAssociatedKey from " ++ show num ++ " (hit)") $ nfIO $ do
+	n <- getStdRandom (randomR (1,num))
+	SQL.getAssociatedKey (fileN n) (SQL.ReadHandle h)
+
+getAssociatedKeyMissBench :: BenchDb -> Benchmark
+getAssociatedKeyMissBench (BenchDb h num) = bench ("getAssociatedKey from " ++ show num ++ " (miss)") $ nfIO $
+	SQL.getAssociatedKey fileMiss (SQL.ReadHandle h)
+
+populateAssociatedFiles :: H.DbQueue -> Int -> IO ()
+populateAssociatedFiles h num = do
+	forM_ [1..num] $ \n ->
+		SQL.addAssociatedFile (keyN n) (fileN n) (SQL.WriteHandle h)
+	H.flushDbQueue h
+
+keyN :: Int -> SKey
+keyN n = SKey ("key" ++ show n)
+
+fileN :: Int -> TopFilePath
+fileN n = asTopFilePath ("file" ++ show n)
+
+keyMiss :: SKey
+keyMiss = keyN 0 -- 0 is never stored
+
+fileMiss :: TopFilePath
+fileMiss = fileN 0 -- 0 is never stored
+
+data BenchDb = BenchDb H.DbQueue Int
+
+benchDb :: FilePath -> Int -> IO BenchDb
+benchDb tmpdir num = do
+	putStrLn $ "setting up database with " ++ show num
+	H.initDb f SQL.createTables
+	h <- H.openDbQueue f SQL.containedTable
+	populateAssociatedFiles h num
+	return (BenchDb h num)
+  where
+	f = tmpdir </> "db" ++ show num
+
+instance NFData TopFilePath where
+	rnf = rnf . getTopFilePath
+
+instance NFData SKey where
+	rnf (SKey s) = rnf s
diff --git a/Common.hs b/Common.hs
index 8272043c2..2b8b9a805 100644
--- a/Common.hs
+++ b/Common.hs
@@ -5,7 +5,7 @@ module Common (module X) where
 import Control.Monad as X
 import Control.Monad.IfElse as X
 import Control.Applicative as X
-import "mtl" Control.Monad.State.Strict as X (liftIO)
+import Control.Monad.IO.Class as X (liftIO)
 
 import Data.Maybe as X
 import Data.List as X hiding (head, tail, init, last)
diff --git a/Database/Keys.hs b/Database/Keys.hs
index a711ba7ca..faf34132a 100644
--- a/Database/Keys.hs
+++ b/Database/Keys.hs
@@ -127,14 +127,13 @@ openDb createdb _ = withExclusiveLock gitAnnexKeysDbLock $ do
 		(False, True) -> do
 			liftIO $ do
 				createDirectoryIfMissing True dbdir
-				H.initDb db $ void $
-					runMigrationSilent SQL.migrateKeysDb
+				H.initDb db SQL.createTables
 			setAnnexDirPerm dbdir
 			setAnnexFilePerm db
 			open db
 		(False, False) -> return DbEmpty
   where
-	open db = liftIO $ DbOpen <$> H.openDbQueue db "content"
+	open db = liftIO $ DbOpen <$> H.openDbQueue db SQL.containedTable
 
 addAssociatedFile :: Key -> TopFilePath -> Annex ()
 addAssociatedFile k f = runWriterIO $ SQL.addAssociatedFile (toSKey k) f
diff --git a/Database/Keys/SQL.hs b/Database/Keys/SQL.hs
index 22bcb86a1..6862b15d9 100644
--- a/Database/Keys/SQL.hs
+++ b/Database/Keys/SQL.hs
@@ -13,6 +13,7 @@
 module Database.Keys.SQL where
 
 import Database.Types
+import Database.Handle
 import qualified Database.Queue as H
 import Utility.InodeCache
 import Git.FilePath
@@ -33,6 +34,12 @@ Content
   KeyCacheIndex key cache
 |]
 
+containedTable :: TableName
+containedTable = "content"
+
+createTables :: SqlPersistM ()
+createTables = void $ runMigrationSilent migrateKeysDb
+
 newtype ReadHandle = ReadHandle H.DbQueue
 
 readDb :: SqlPersistM a -> ReadHandle -> IO a
diff --git a/doc/git-annex.mdwn b/doc/git-annex.mdwn
index 299428d1e..329fb8932 100644
--- a/doc/git-annex.mdwn
+++ b/doc/git-annex.mdwn
@@ -672,6 +672,11 @@ subdirectories).
   
   See [[git-annex-fuzztest]](1) for details.
 
+* `benchmark`
+
+  This runs git-annex's built-in benchmarks, if it was built with
+  benchmarking support.
+
 # COMMON OPTIONS
 
 These common options are accepted by all git-annex commands, and
diff --git a/doc/todo/smudge.mdwn b/doc/todo/smudge.mdwn
index 6498863e4..5f3d521bf 100644
--- a/doc/todo/smudge.mdwn
+++ b/doc/todo/smudge.mdwn
@@ -32,14 +32,6 @@ git-annex should use smudge/clean filters.
   when pushing changes committed in such a repo. Ideally, should avoid
   committing implicit unlocks, or should prevent such commits leaking out
   in pushes.
-* Optimisation: See if the database schema can be improved to speed things
-  up. Are there enough indexes? getAssociatedKey in particular does a
-  reverse lookup and might benefit from an index.
-* Optimisation: Reads from the Keys database avoid doing anything if the
-  database doesn't exist. This makes v5 repos, or v6 with all locked files
-  faster. However, if a v6 repo unlocks and then re-locks a file, its
-  database will exist, and so this optimisation will no longer apply.
-  Could try to detect when the database is empty, and remove it or avoid reads.
 
 * Eventually (but not yet), make v6 the default for new repositories.
   Note that the assistant forces repos into direct mode; that will need to
diff --git a/git-annex.cabal b/git-annex.cabal
index 5c09a0c61..289e7a255 100644
--- a/git-annex.cabal
+++ b/git-annex.cabal
@@ -88,6 +88,10 @@ Flag EKG
   Description: Enable use of EKG to monitor git-annex as it runs (at http://localhost:4242/)
   Default: False
 
+Flag Benchmark
+  Description: Enable benchmarking
+  Default: False
+
 Flag network-uri
   Description: Get Network.URI from the network-uri package
   Default: True
@@ -260,6 +264,10 @@ Executable git-annex
     Build-Depends: ekg
     GHC-Options: -with-rtsopts=-T
     CPP-Options: -DWITH_EKG
+  
+  if flag(Benchmark)
+    Build-Depends: criterion, deepseq
+    CPP-Options: -DWITH_BENCHMARK
 
 source-repository head
   type: git