avoid reposize database locking overhead when not needed

Only when the preferred content expression being matched uses balanced
preferred content is this overhead needed.

It might be possible to eliminate the locking entirely. Eg, check the
live changes before and after the action and re-run if they are not
stable. For now, this is good enough, it avoids existing preferred
content getting slow. If balanced preferred content turns out to be too
slow to check, that could be tried later.

Annex/FileMatcher.hs

@@ -90,7 +90,7 @@ checkMatcher matcher mkey afile lu notpresent notconfigured d
 
 checkMatcher' :: FileMatcher Annex -> MatchInfo -> LiveUpdate -> AssumeNotPresent -> Annex Bool
 checkMatcher' (matcher, (MatcherDesc matcherdesc)) mi lu notpresent =
-	checkLiveUpdate lu go
+	checkLiveUpdate lu matcher go
   where
 	go = do
 		(matches, desc) <- runWriterT $ matchMrun' matcher $ \op ->
@@ -281,6 +281,7 @@ call desc (Right sub) = Right $ Operation $ MatchFiles
 	, matchNeedsFileContent = any matchNeedsFileContent sub
 	, matchNeedsKey = any matchNeedsKey sub
 	, matchNeedsLocationLog = any matchNeedsLocationLog sub
+	, matchNeedsLiveRepoSize = any matchNeedsLiveRepoSize sub
 	, matchDesc = matchDescSimple desc
 	}
 call _ (Left err) = Left err

Annex/RepoSize/LiveUpdate.hs

@@ -13,6 +13,8 @@ import Annex.Common
 import Logs.Presence.Pure
 import qualified Database.RepoSize as Db
 import Annex.UUID
+import Types.FileMatcher
+import qualified Utility.Matcher as Matcher
 
 import Control.Concurrent
 import System.Process
@@ -95,9 +97,16 @@ needLiveUpdate lu = liftIO $ void $ tryPutMVar (liveUpdateNeeded lu) ()
 -- This serializes calls to the action, so that if the action
 -- queries getLiveRepoSizes it will not race with another such action
 -- that may also be starting a live update.
-checkLiveUpdate :: LiveUpdate -> Annex Bool -> Annex Bool
+checkLiveUpdate
-checkLiveUpdate NoLiveUpdate a = a
+	:: LiveUpdate
-checkLiveUpdate lu a = Db.lockDbWhile (const go) go
+	-> Matcher.Matcher (MatchFiles Annex)
+	-> Annex Bool
+	-> Annex Bool
+checkLiveUpdate NoLiveUpdate _ a = a
+checkLiveUpdate lu matcher a
+	| Matcher.introspect matchNeedsLiveRepoSize matcher =
+		Db.lockDbWhile (const go) go
+	| otherwise = a
   where
 	go = do
 		r <- a

Limit.hs

@@ -114,6 +114,7 @@ limitInclude glob = Right $ MatchFiles
 	, matchNeedsFileContent = False
 	, matchNeedsKey = False
 	, matchNeedsLocationLog = False
+	, matchNeedsLiveRepoSize = False
 	, matchDesc = "include" =? glob
 	}
 
@@ -128,6 +129,7 @@ limitExclude glob = Right $ MatchFiles
 	, matchNeedsFileContent = False
 	, matchNeedsKey = False
 	, matchNeedsLocationLog = False
+	, matchNeedsLiveRepoSize = False
 	, matchDesc = "exclude" =? glob
 	}
 
@@ -153,6 +155,7 @@ limitIncludeSameContent glob = Right $ MatchFiles
 	, matchNeedsFileContent = False
 	, matchNeedsKey = False
 	, matchNeedsLocationLog = False
+	, matchNeedsLiveRepoSize = False
 	, matchDesc = "includesamecontent" =? glob
 	}
 
@@ -168,6 +171,7 @@ limitExcludeSameContent glob = Right $ MatchFiles
 	, matchNeedsFileContent = False
 	, matchNeedsKey = False
 	, matchNeedsLocationLog = False
+	, matchNeedsLiveRepoSize = False
 	, matchDesc = "excludesamecontent" =? glob
 	}
 
@@ -244,6 +248,7 @@ matchMagic limitname querymagic selectprovidedinfo selectuserprovidedinfo (Just
 		, matchNeedsFileContent = True
 		, matchNeedsKey = False
 		, matchNeedsLocationLog = False
+		, matchNeedsLiveRepoSize = False
 		, matchDesc = limitname =? glob
 		}
   where
@@ -271,6 +276,7 @@ addUnlocked = addLimit $ Right $ MatchFiles
 	, matchNeedsFileContent = False
 	, matchNeedsKey = False
 	, matchNeedsLocationLog = False
+	, matchNeedsLiveRepoSize = False
 	, matchDesc = matchDescSimple "unlocked"
 	}
 
@@ -281,6 +287,7 @@ addLocked = addLimit $ Right $ MatchFiles
 	, matchNeedsFileContent = False
 	, matchNeedsKey = False
 	, matchNeedsLocationLog = False
+	, matchNeedsLiveRepoSize = False
 	, matchDesc = matchDescSimple "locked"
 	}
 
@@ -316,6 +323,7 @@ addIn s = do
 		, matchNeedsFileContent = False
 		, matchNeedsKey = True
 		, matchNeedsLocationLog = not inhere
+		, matchNeedsLiveRepoSize = False
 		, matchDesc = "in" =? s
 		}
 	checkinuuid u notpresent key
@@ -346,6 +354,7 @@ addExpectedPresent = do
 		, matchNeedsFileContent = False
 		, matchNeedsKey = True
 		, matchNeedsLocationLog = True
+		, matchNeedsLiveRepoSize = False
 		, matchDesc = matchDescSimple "expected-present"
 		}
 
@@ -363,6 +372,7 @@ limitPresent u = MatchFiles
 	, matchNeedsFileContent = False
 	, matchNeedsKey = True
 	, matchNeedsLocationLog = not (isNothing u)
+	, matchNeedsLiveRepoSize = False
 	, matchDesc = matchDescSimple "present"
 	}
 
@@ -374,6 +384,7 @@ limitInDir dir desc = MatchFiles
 	, matchNeedsFileContent = False
 	, matchNeedsKey = False
 	, matchNeedsLocationLog = False
+	, matchNeedsLiveRepoSize = False
 	, matchDesc = matchDescSimple desc
 	}
   where
@@ -406,6 +417,7 @@ limitCopies want = case splitc ':' want of
 			, matchNeedsFileContent = False
 			, matchNeedsKey = True
 			, matchNeedsLocationLog = True
+			, matchNeedsLiveRepoSize = False
 			, matchDesc = "copies" =? want
 			}
 	go' n good notpresent key = do
@@ -431,6 +443,7 @@ limitLackingCopies desc approx want = case readish want of
 		, matchNeedsFileContent = False
 		, matchNeedsKey = True
 		, matchNeedsLocationLog = True
+		, matchNeedsLiveRepoSize = False
 		, matchDesc = matchDescSimple desc
 		}
 	Nothing -> Left "bad value for number of lacking copies"
@@ -461,6 +474,7 @@ limitUnused = MatchFiles
 	, matchNeedsFileContent = False
 	, matchNeedsKey = True
 	, matchNeedsLocationLog = False
+	, matchNeedsLiveRepoSize = False
 	, matchDesc = matchDescSimple "unused"
 	}
   where
@@ -484,6 +498,7 @@ limitAnything = MatchFiles
 	, matchNeedsFileContent = False
 	, matchNeedsKey = False
 	, matchNeedsLocationLog = False
+	, matchNeedsLiveRepoSize = False
 	, matchDesc = matchDescSimple "anything"
 	}
 
@@ -499,6 +514,7 @@ limitNothing = MatchFiles
 	, matchNeedsFileContent = False
 	, matchNeedsKey = False
 	, matchNeedsLocationLog = False
+	, matchNeedsLiveRepoSize = False
 	, matchDesc = matchDescSimple "nothing"
 	}
 
@@ -522,6 +538,7 @@ limitInAllGroup getgroupmap groupname = Right $ MatchFiles
 	, matchNeedsFileContent = False
 	, matchNeedsKey = True
 	, matchNeedsLocationLog = True
+	, matchNeedsLiveRepoSize = False
 	, matchDesc = "inallgroup" =? groupname
 	}
   where
@@ -547,6 +564,7 @@ limitOnlyInGroup getgroupmap groupname = Right $ MatchFiles
 	, matchNeedsFileContent = False
 	, matchNeedsKey = True
 	, matchNeedsLocationLog = True
+	, matchNeedsLiveRepoSize = False
 	, matchDesc = "inallgroup" =? groupname
 	}
   where
@@ -592,6 +610,7 @@ limitBalanced' termname fullybalanced mu groupname = do
 			matchNeedsLocationLog present ||
 			matchNeedsLocationLog fullybalanced ||
 			matchNeedsLocationLog copies
+		, matchNeedsLiveRepoSize = True
 		, matchDesc = termname =? groupname
 		}
 
@@ -677,6 +696,7 @@ limitFullyBalanced''' filtercandidates termname mu getgroupmap g n want = Right
 	, matchNeedsFileContent = False
 	, matchNeedsKey = True
 	, matchNeedsLocationLog = False
+	, matchNeedsLiveRepoSize = True
 	, matchDesc = termname =? want
 	}
 
@@ -736,6 +756,7 @@ limitInBackend name = Right $ MatchFiles
 	, matchNeedsFileContent = False
 	, matchNeedsKey = True
 	, matchNeedsLocationLog = False
+	, matchNeedsLiveRepoSize = False
 	, matchDesc = "inbackend" =? name
 	}
   where
@@ -753,6 +774,7 @@ limitSecureHash = MatchFiles
 	, matchNeedsFileContent = False
 	, matchNeedsKey = True
 	, matchNeedsLocationLog = False
+	, matchNeedsLiveRepoSize = False
 	, matchDesc = matchDescSimple "securehash"
 	}
 
@@ -774,6 +796,7 @@ limitSize lb desc vs s = case readSize dataUnits s of
 		, matchNeedsFileContent = False
 		, matchNeedsKey = False
 		, matchNeedsLocationLog = False
+		, matchNeedsLiveRepoSize = False
 		, matchDesc = desc =? s
 		}
   where
@@ -804,6 +827,7 @@ limitMetaData s = case parseMetaDataMatcher s of
 		, matchNeedsFileContent = False
 		, matchNeedsKey = True
 		, matchNeedsLocationLog = False
+		, matchNeedsLiveRepoSize = False
 		, matchDesc = "metadata" =? s
 		}
   where
@@ -820,6 +844,7 @@ addAccessedWithin duration = do
 		, matchNeedsFileContent = False
 		, matchNeedsKey = False
 		, matchNeedsLocationLog = False
+		, matchNeedsLiveRepoSize = False
 		, matchDesc = "accessedwithin" =? fromDuration duration
 		}
   where

Limit/Wanted.hs

@@ -40,12 +40,14 @@ addPreferredContentLimit desc a = do
 	nfc <- introspectPreferredRequiredContent matchNeedsFileContent Nothing
 	nk <- introspectPreferredRequiredContent matchNeedsKey Nothing
 	nl <- introspectPreferredRequiredContent matchNeedsLocationLog Nothing
+	lsz <- introspectPreferredRequiredContent matchNeedsLiveRepoSize Nothing
 	addLimit $ Right $ MatchFiles
 		{ matchAction = const $ const a
 		, matchNeedsFileName = nfn
 		, matchNeedsFileContent = nfc
 		, matchNeedsKey = nk
 		, matchNeedsLocationLog = nl
+		, matchNeedsLiveRepoSize = lsz
 		, matchDesc = matchDescSimple desc
 		}
 

Types/FileMatcher.hs

@@ -96,6 +96,8 @@ data MatchFiles a = MatchFiles
 	-- ^ does the matchAction look at information about the key?
 	, matchNeedsLocationLog :: Bool
 	-- ^ does the matchAction look at the location log?
+	, matchNeedsLiveRepoSize :: Bool
+	-- ^ does the matchAction need live repo size information?
 	, matchDesc :: Bool -> MatchDesc
 	-- ^ displayed to the user to describe whether it matched or not
 	}

doc/todo/git-annex_proxies.mdwn

@@ -37,14 +37,6 @@ Planned schedule of work:
 
 * Test that live repo size data is correct and really works.
 
-* Avoid using checkLiveUpdate except when checking a preferred content
-  expression that does use balanced preferred content. No reason to pay
-  its time penalty otherwise.
-
-  Alternatively, make it not use file locking. It could rely on a database
-  transaction, or it could check the live changes before and after and
-  re-run the Annex action if they are not stable.
-
 * When loading the live update table, check if PIDs in it are still
   running (and are still git-annex), and if not, remove stale entries
   from it, which can accumulate when processes are interrupted.