.

go/neo/client/cache.go

@@ -252,10 +252,7 @@ func (c *Cache) Load(xid zodb.Xid) (data []byte, tid zodb.Tid, err error) {
 		c.gcMu.Lock()
 		rce.inLRU.MoveBefore(&c.lru)
 		c.gcMu.Unlock()
-
-		// XXX for ErrXidMissing xtid needs to be adjusted to what was queried by user
-
-		return rce.data, rce.serial, rce.err
+		return rce.data, rce.serial, rce.userErr(xid)
 	}
 
 	// entry was not in cache - this goroutine becomes responsible for loading it
@@ -287,7 +284,7 @@ func (c *Cache) Load(xid zodb.Xid) (data []byte, tid zodb.Tid, err error) {
 		// rce was already dropped by merge / evicted
 		// (XXX recheck about evicted)
 		oce.Unlock()
-		return rce.data, rce.serial, rce.err
+		return rce.data, rce.serial, rce.userErr(xid)
 	}
 
 	// if rce & rceNext cover the same range -> drop rce
@@ -320,7 +317,7 @@ func (c *Cache) Load(xid zodb.Xid) (data []byte, tid zodb.Tid, err error) {
 	}
 	c.gcMu.Unlock()
 
-	return rce.data, rce.serial, rce.err
+	return rce.data, rce.serial, rce.userErr(xid)
 }
 
 // tryMerge tries to merge rce prev into next
@@ -345,7 +342,9 @@ func tryMerge(prev, next, cur *revCacheEntry, oid zodb.Oid) bool {
 	//	Pok  Nok    Ns < Pb         Ps  = Ns
 	//	Pe   Nok    Ns < Pb         Pe != "nodata"	(e.g. it was IO loading error for P)
 	//	Pok  Ne       ---
-	//	Ne   Pe     (Pe="nodata") = (Ne="nodata")
+	//	Ne   Pe     (Pe="nodata") = (Ne="nodata")	-> XXX vs deleteObject?
+	//							-> let deleted object actually read
+	//							-> as special non-error value
 	//
 	// b - before
 	// s - serial
@@ -428,6 +427,21 @@ func (rce *revCacheEntry) loaded() bool {
 	}
 }
 
+// userErr returns error that, if any, needs to be returned to user from Cache.Load
+//
+// ( ErrXidMissing containts xid for which it is missing. In cache we keep such
+//   xid with max .before but users need to get ErrXidMissing with their own query )
+func (rce *revCacheEntry) userErr(xid zodb.Xid) error {
+	switch e := rce.err.(type) {
+	case *zodb.ErrXidMissing:
+		if e.Xid != xid {
+			return &zodb.ErrXidMissing{xid}
+		}
+	}
+
+	return rce.err
+}
+
 // revCacheEntry: .inLRU -> .
 func (h *listHead) rceFromInLRU() (rce *revCacheEntry) {
 	urce := unsafe.Pointer(uintptr(unsafe.Pointer(h)) - unsafe.Offsetof(rce.inLRU))

go/neo/client/cache_test.go

@@ -80,12 +80,20 @@ func (s *tStorage) Load(xid zodb.Xid) (data []byte, serial zodb.Tid, err error)
 var tstor = &tStorage{
 	dataMap: map[zodb.Oid][]tOidData{
 		1: {
-			{3, []byte("hello")},
+			{4, []byte("hello")},
 			{7, []byte("world")},
 		},
 	},
 }
 
+func xidlt(oid zodb.Oid, tid zodb.Tid) zodb.Xid {
+	return zodb.Xid{Oid: oid, XTid: zodb.XTid{Tid: tid, TidBefore: true}}
+}
+
+func xideq(oid zodb.Oid, tid zodb.Tid) zodb.Xid {
+	return zodb.Xid{Oid: oid, XTid: zodb.XTid{Tid: tid, TidBefore: false}}
+}
+
 func TestCache(t *testing.T) {
 	// XXX <100 <90 <80
 	//	q<110	-> a) 110 <= cache.before   b) otherwise
@@ -107,28 +115,39 @@ func TestCache(t *testing.T) {
 	// XXX hack; place=ok?
 	pretty.CompareConfig.PrintStringers = true
 
-	xid1 := zodb.Xid{Oid: 1, XTid: zodb.XTid{Tid: 2, TidBefore: true}}
-	data, serial, err := c.Load(xid1)	// -> nil, 0, &zodb.ErrXidMissing{1,<2}
+	// XXX vvv -> checkLoad()
+	data, serial, err := c.Load(xidlt(1,3))
 	ok1(data == nil)
 	ok1(serial == 0)
-	eq(err, &zodb.ErrXidMissing{xid1})
+	eq(err, &zodb.ErrXidMissing{xidlt(1,3)})
 
 	oce1 := c.entryMap[1]
 	ok1(len(oce1.revv) == 1)
-	rce1_b2 := oce1.revv[0]
-	ok1(rce1_b2.before == 2)
-	ok1(rce1_b2.serial == 0)
-	eq(rce1_b2.err, &zodb.ErrXidMissing{xid1})	// XXX must be 1, ?0
-
-	xid1_3 := xid1
-	xid1_3.Tid = 3
-	data, serial, err = c.Load(xid1_3) // -> nil, 0, zodb.ErrXidMissing{1,<3}
+	// XXX vvv -> checkRCE ?
+	rce1_b3 := oce1.revv[0]
+	ok1(rce1_b3.before == 3)
+	ok1(rce1_b3.serial == 0)
+	eq(rce1_b3.err, &zodb.ErrXidMissing{xidlt(1,3)})	// XXX must be 1, ?0
+
+	data, serial, err = c.Load(xidlt(1,4))
+	ok1(data == nil)
+	ok1(serial == 0)
+	eq(err, &zodb.ErrXidMissing{xidlt(1,4)})
+
+	ok1(len(oce1.revv) == 1)
+	rce1_b4 := oce1.revv[0]
+	ok1(rce1_b4 != rce1_b3) // rce1_b3 was merged into rce1_b4
+	ok1(rce1_b4.before == 4)
+	ok1(rce1_b4.serial == 0)
+	eq(rce1_b4.err, &zodb.ErrXidMissing{xidlt(1,4)})	// XXX must be 1, ?0
+
+	// XXX load <2 -> check it is merged with <4	XXX vs deleteObject?
+	data, serial, err = c.Load(xidlt(1,2))
 	ok1(data == nil)
 	ok1(serial == 0)
-	eq(err, &zodb.ErrXidMissing{xid1_3})
-	eq(len(oce1.revv), 1)
-	rce1_b3 := oce1.revv[0]
-	ok1(rce1_b3 != rce1_b2) // rce1_b2 was merged into rce1_b3
+	fmt.Println(err)
+	eq(err, &zodb.ErrXidMissing{xidlt(1,2)})
+
 }
 
 type Checker struct {