Bug Fix:

Copy over vs.value into item.vptr, otherwise, when item gets reused it
ends up overwriting a value pointer and cause panics. This is the bug
which ventured into v1.0.6 of Dgraph, and caused hard to locate panics.

Author: manishrjain

db.go

@@ -100,7 +100,7 @@ func replayFunction(out *DB) func(Entry, valuePointer) error {
 	first := true
 	return func(e Entry, vp valuePointer) error { // Function for replaying.
 		if first {
-			out.elog.Printf("First key=%s\n", e.Key)
+			out.elog.Printf("First key=%q\n", e.Key)
 		}
 		first = false
 

iterator.go

@@ -182,9 +182,13 @@ func (item *Item) yieldItemValue() ([]byte, func(), error) {
 		if vs.Version != item.Version() {
 			return nil, nil, nil
 		}
-		item.vptr = vs.Value
+		// Bug fix: Always copy the vs.Value into vptr here. Otherwise, when item is reused this
+		// slice gets overwritten.
+		item.vptr = y.SafeCopy(item.vptr, vs.Value)
 		item.meta &^= bitValuePointer // Clear the value pointer bit.
-		item.meta |= vs.Meta          // This meta would only be about value pointer.
+		if vs.Meta&bitValuePointer > 0 {
+			item.meta |= bitValuePointer // This meta would only be about value pointer.
+		}
 	}
 }