.

go/zodb/db.go

@@ -48,16 +48,26 @@ type DB struct {
 	stor IStorage
 
 	mu    sync.Mutex
+
+	// connections nearby current db
+	// XXX covered by δtail
+	// live cache is reused through finding conn with nearby at and
+	// invalidating live objects based on δtail info.
 	connv []*Connection // order by ↑= .at
 
-	// XXX -> Storage. XXX or -> Cache? (so it is not duplicated many times for many DB case)
+	// // connections that are too far away from current db
+	// // not covered by δtail
+	// historicv []*Connections	// XXX needed? (think again)
 
 	// δtail of database changes for invalidations
 	// min(rev) = min(conn.at) for all conn ∈ db (opened and in the pool)
+	// XXX      + min(conn.at) for all conn ∈ waiting/opening.
 	δtail *ΔTail // [](rev↑, []oid)
 
 	// openers waiting for δtail.Head to become covering their at.
 	δwait map[δwaiter]struct{} // set{(at, ready)}	XXX -> set_δwaiter?
+
+	// XXX δtail/δwait -> Storage. XXX or -> Cache? (so it is not duplicated many times for many DB case)
 }
 
 // δwaiter represents someone waiting for δtail.Head to become ≥ at.
@@ -175,12 +185,13 @@ func (db *DB) Open(ctx context.Context, opt *ConnOptions) (_ *Connection, err er
 		head := Tid(0)
 
 		if opt.NoSync {
-			// XXX locking
-			// XXX prevent retrieved head to be removed from δtail
-			head = db.δtail.Head()	// = 0 if empty
+			db.mu.Lock()
+			// XXX prevent retrieved head to be removed from δtail ?
+			head = db.δtail.Head()	// = 0 if δtail was not yet initialized with first event
+			db.mu.Unlock()
 		}
 
-		// !NoSync or δtail empty
+		// !NoSync or δtail !initialized
 		// sync storage for lastTid
 		if head == 0 {
 			var err error
@@ -197,6 +208,52 @@ func (db *DB) Open(ctx context.Context, opt *ConnOptions) (_ *Connection, err er
 		at = head
 	}
 
+	db.mu.Lock()
+
+	// check if we already have the exact match
+	conn = db.get(at, at)
+
+	if conn == nil {
+		switch {
+		// too far in the past -> historic connection
+		case at < db.δtail.Tail():
+			//conn = db.get(at, at)
+			conn = newConnection(db, at)
+
+		// δtail !initialized yet
+		case db.δtail.Head() == 0:
+			// XXX δtail could be not yet initialized, but e.g. last_tid changed
+			//     -> we have to wait for δtail not to loose just-released live cache
+			conn = newConnection(db, at)
+
+		// we already have some history coverage
+		default:
+			if at > δhead {
+				// XXX wait
+				// XXX -> retry loop (δtail.tail might go over at)
+			}
+
+			// at ∈ [δtail, δhead]
+			conn = get(δtail.Tail(), at)
+			if conn == nil {
+				conn = newConnection(db, at)
+			} else {
+				// invalidate changed live objects
+				for _, δ := range δtail.Slice(conn.at, at) {
+					for _, oid := range δ.changev {
+						obj := conn.cache.Get(oid)
+						if obj != nil {
+							obj.PInvalidate()
+						}
+					}
+				}
+
+				conn.at = at
+			}
+		}
+
+		db.mu.Unlock()
+
 		// wait till .δtail.head is up to date covering ≥ at
 		var δready chan struct{}
 		db.mu.Lock()
@@ -217,6 +274,7 @@ func (db *DB) Open(ctx context.Context, opt *ConnOptions) (_ *Connection, err er
 				// ok
 			}
 		}
+	}
 
 	// now we have both at and invalidation data covering it -> proceed to
 	// get connection from the pool.
@@ -229,11 +287,14 @@ func (db *DB) Open(ctx context.Context, opt *ConnOptions) (_ *Connection, err er
 
 // get returns connection from db pool most close to at.
 //
-// it creates new one if there is no close-enough connection in the pool.
+// it creates new one if there is no close-enough connection in the pool.	XXX -> no
+// XXX -> must be run with db.mu locked.
 func (db *DB) get(at Tid) *Connection {
 	db.mu.Lock()
 	defer db.mu.Unlock()
 
+	// XXX at < δtail.Tail -> getHistoric; else -> here
+
 	l := len(db.connv)
 
 	// find connv index corresponding to at:

go/zodb/δtail.go

@@ -56,17 +56,11 @@ import (
 //	#blk - file block number, when ΔTail represents changes to a file.
 type ΔTail struct {
 	head  Tid
-	tailv []δRevEntry
+	tailv []CommitEvent
 
 	lastRevOf map[Oid]Tid // index for LastRevOf queries
 	// TODO also add either tailv idx <-> rev index, or lastRevOf -> tailv idx
-	// (if linear back-scan of δRevEntry starts to eat cpu).
-}
-
-// δRevEntry represents information of what have been changed in one revision.
-type δRevEntry struct {
-	rev     Tid
-	changev []Oid
+	// (if linear back-scan of CommitEvent starts to eat cpu).
 }
 
 // NewΔTail creates new ΔTail object.
@@ -82,7 +76,39 @@ func (δtail *ΔTail) Head() Tid {
 	return δtail.head
 }
 
-// XXX + Tail?
+// XXX doc	XXX tests	XXX Tail -> End? Back?
+func (δtail *ΔTail) Tail() Tid {
+	if len(δtail.tailv) > 0 {
+		return δtail.tailv[0].rev
+	}
+	return δtail.head
+}
+
+// XXX -> git tailv subslice in (low, high]
+// XXX tail <= low <= high <= head, else panic
+func (δtail *ΔTail) Slice(low, high Tid) []CommitEvent {
+	tail := δtail.Tail()
+	head := δtail.head
+	if !(tail <= low && low <= high && high <= head) {
+		panic(fmt.Sprintf("δtail.Slice: (%s, %s] invalid; tail..head = %s..%s", low, high, tail, head))
+	}
+
+	// ex (0,0] tail..head = 0..0
+	if len(tailv) == 0 {
+		return tailv
+	}
+
+	// find max j : [j].rev <= high
+	j := len(tailv)-1
+	for ; tailv[j].rev > high; j-- {}
+
+	// find max i : [i].rev > low
+	i := j
+	for ; i >= 0 && tailv[i].rev > low; i-- {}
+	i++
+
+	return tailv[i:j]
+}
 
 // XXX add way to extend coverage without appending changed data? (i.e. if a
 // txn did not change file at all) -> but then it is simply .Append(rev, nil)?
@@ -97,7 +123,7 @@ func (δtail *ΔTail) Append(rev Tid, changev []Oid) {
 	}
 
 	δtail.head = rev
-	δtail.tailv = append(δtail.tailv, δRevEntry{rev, changev})
+	δtail.tailv = append(δtail.tailv, CommitEvent{rev, changev})
 	for _, id := range changev {
 		δtail.lastRevOf[id] = rev
 	}
@@ -125,7 +151,7 @@ func (δtail *ΔTail) ForgetBefore(revCut Tid) {
 	// 1) growing underlying storage array indefinitely
 	// 2) keeping underlying storage after forget
 	l := len(δtail.tailv)-icut
-	tailv := make([]δRevEntry, l)
+	tailv := make([]CommitEvent, l)
 	copy(tailv, δtail.tailv[icut:])
 	δtail.tailv = tailv
 }

go/zodb/δtail.go.cat-generic

@@ -29,7 +29,7 @@
 # The types that are emitted are
 #
 #	ΔTail
-#	δRevEntry
+#	ΔRevEntry
 
 input=$(dirname $0)/δtail.go
 
@@ -37,4 +37,14 @@ cat "$input" |sed	\
 	-e 's/package zodb/package PACKAGE/g'	\
 	-e '/package PACKAGE/a \\nimport "lab.nexedi.com/kirr/neo/go/zodb"'	\
 	-e 's/Tid/zodb.Tid/g'	\
-	-e 's/Oid/ID/g'
+	-e 's/Oid/ID/g'		\
+	-e 's/CommitEvent/ΔRevEntry/g'
+
+cat <<EOF
+
+// ΔRevEntry represents information of what have been changed in one revision.
+type ΔRevEntry struct {
+	Rev     Tid
+	Changev []ID
+}
+EOF