Fast Cache Migration (#9)

* implement nodedb changes to set and get chain version from the database

* implement and unit test upgrade to fast storage in mutable tree

* refactor for auto upgrade to fast version in mutable tree contructor, load version and lazy load version

* use proper functionality for getting latest version

* remove unused error

* fix comment

* use fast version value in tests

* spurious tab

* fix style problems and remove redundant code in tests

go.mod

@@ -6,6 +6,7 @@ require (
 	github.com/confio/ics23/go v0.6.6
 	github.com/gogo/gateway v1.1.0
 	github.com/gogo/protobuf v1.3.2
+	github.com/golang/mock v1.6.0 // indirect
 	github.com/golang/protobuf v1.5.2
 	github.com/grpc-ecosystem/go-grpc-middleware v1.3.0
 	github.com/grpc-ecosystem/grpc-gateway v1.16.0

go.sum

@@ -310,6 +310,7 @@ github.com/golang/mock v1.4.1/go.mod h1:UOMv5ysSaYNkG+OFQykRIcU/QvvxJf3p21QfJ2Bt
 github.com/golang/mock v1.4.3/go.mod h1:UOMv5ysSaYNkG+OFQykRIcU/QvvxJf3p21QfJ2Bt3cw=
 github.com/golang/mock v1.4.4/go.mod h1:l3mdAwkq5BuhzHwde/uurv3sEJeZMXNpwsxVWU71h+4=
 github.com/golang/mock v1.5.0/go.mod h1:CWnOUgYIOo4TcNZ0wHX3YZCqsaM1I1Jvs6v3mP3KVu8=
+github.com/golang/mock v1.6.0 h1:ErTB+efbowRARo13NNdxyJji2egdxLGQhRaY+DUumQc=
 github.com/golang/mock v1.6.0/go.mod h1:p6yTPP+5HYm5mzsMV8JkE6ZKdX+/wYM6Hr+LicevLPs=
 github.com/golang/protobuf v1.1.0/go.mod h1:6lQm79b+lXiMfvg/cZm0SGofjICqVBUtrP5yJMmIC1U=
 github.com/golang/protobuf v1.2.0/go.mod h1:6lQm79b+lXiMfvg/cZm0SGofjICqVBUtrP5yJMmIC1U=

immutable_tree.go

@@ -109,8 +109,8 @@ func (t *ImmutableTree) Version() int64 {
 	return t.version
 }
 
-// IsLatestVersion returns true if curren tree is of the latest version, false otherwise.
-func (t *ImmutableTree) IsLatestVersion() bool {
+// IsLatestTreeVersion returns true if curren tree is of the latest version, false otherwise.
+func (t *ImmutableTree) IsLatestTreeVersion() bool {
 	return t.version == t.ndb.getLatestVersion()
 }
 
@@ -236,8 +236,7 @@ func (t *ImmutableTree) Iterate(fn func(key []byte, value []byte) bool) bool {
 
 // Iterator returns an iterator over the immutable tree.
 func (t *ImmutableTree) Iterator(start, end []byte, ascending bool) dbm.Iterator {
-	isFastTraversal := t.IsLatestVersion()
-	if isFastTraversal {
+	if t.IsFastCacheEnabled() {
 		return NewFastIterator(start, end, ascending, t.ndb)
 	} else {
 		return NewIterator(start, end, ascending, t)
@@ -259,6 +258,16 @@ func (t *ImmutableTree) IterateRange(start, end []byte, ascending bool, fn func(
 	})
 }
 
+// GetStorageVersion returns the version of the underlying storage.
+func (t *ImmutableTree) GetStorageVersion() (string) {
+	return t.ndb.getStorageVersion()
+}
+
+// IsFastCacheEnabled returns true if fast storage is enabled, false otherwise.
+func (t *ImmutableTree) IsFastCacheEnabled() bool {
+	return t.IsLatestTreeVersion() && t.ndb.isFastStorageEnabled()
+}
+
 // IterateRangeInclusive makes a callback for all nodes with key between start and end inclusive.
 // If either are nil, then it is open on that side (nil, nil is the same as Iterate). The keys and
 // values must not be modified, since they may point to data stored within IAVL.