refactor(store/v2): Use Core Iterator (#18957)

Co-authored-by: marbar3778 <marbar3778@yahoo.com>
Co-authored-by: cool-developer <51834436+cool-develope@users.noreply.github.com>

core/store/store.go

@@ -30,32 +30,15 @@ type KVStore interface {
 	ReverseIterator(start, end []byte) (Iterator, error)
 }
 
-// Iterator represents an iterator over a domain of keys. Callers must call Close when done.
-// No writes can happen to a domain while there exists an iterator over it, some backends may take
-// out database locks to ensure this will not happen.
+// Iterator represents an iterator over a domain of keys. Callers must call
+// Close when done. No writes can happen to a domain while there exists an
+// iterator over it. Some backends may take out database locks to ensure this
+// will not happen.
 //
-// Callers must make sure the iterator is valid before calling any methods on it, otherwise
-// these methods will panic. This is in part caused by most backend databases using this convention.
-//
-// As with DB, keys and values should be considered read-only, and must be copied before they are
-// modified.
-//
-// Typical usage:
-//
-// var itr Iterator = ...
-// defer itr.Close()
-//
-//	for ; itr.Valid(); itr.Next() {
-//	  k, v := itr.Key(); itr.Value()
-//	  ...
-//	}
-//
-//	if err := itr.Error(); err != nil {
-//	  ...
-//	}
+// Callers must make sure the iterator is valid before calling any methods on it,
+// otherwise these methods will panic.
 type Iterator interface {
 	// Domain returns the start (inclusive) and end (exclusive) limits of the iterator.
-	// CONTRACT: start, end readonly []byte
 	Domain() (start, end []byte)
 
 	// Valid returns whether the current iterator is valid. Once invalid, the Iterator remains
@@ -67,12 +50,13 @@ type Iterator interface {
 	Next()
 
 	// Key returns the key at the current position. Panics if the iterator is invalid.
-	// CONTRACT: key readonly []byte
-	Key() (key []byte)
+	// Note, the key returned should be a copy and thus safe for modification.
+	Key() []byte
 
-	// Value returns the value at the current position. Panics if the iterator is invalid.
-	// CONTRACT: value readonly []byte
-	Value() (value []byte)
+	// Value returns the value at the current position. Panics if the iterator is
+	// invalid.
+	// Note, the value returned should be a copy and thus safe for modification.
+	Value() []byte
 
 	// Error returns the last error encountered by the iterator, if any.
 	Error() error
@@ -80,3 +64,15 @@ type Iterator interface {
 	// Close closes the iterator, releasing any allocated resources.
 	Close() error
 }
+
+// IteratorCreator defines an interface for creating forward and reverse iterators.
+type IteratorCreator interface {
+	// Iterator creates a new iterator for the given store name and domain, where
+	// domain is defined by [start, end). Note, both start and end are optional.
+	Iterator(storeKey string, start, end []byte) (Iterator, error)
+
+	// ReverseIterator creates a new reverse iterator for the given store name
+	// and domain, where domain is defined by [start, end). Note, both start and
+	// end are optional.
+	ReverseIterator(storeKey string, start, end []byte) (Iterator, error)
+}

store/database.go

@@ -3,6 +3,7 @@ package store
 import (
 	"io"
 
+	corestore "cosmossdk.io/core/store"
 	ics23 "github.com/cosmos/ics23/go"
 )
 
@@ -38,7 +39,7 @@ type Writer interface {
 type Database interface {
 	Reader
 	Writer
-	IteratorCreator
+	corestore.IteratorCreator
 	io.Closer
 }
 
@@ -50,8 +51,8 @@ type VersionedDatabase interface {
 	GetLatestVersion() (uint64, error)
 	SetLatestVersion(version uint64) error
 
-	Iterator(storeKey string, version uint64, start, end []byte) (Iterator, error)
-	ReverseIterator(storeKey string, version uint64, start, end []byte) (Iterator, error)
+	Iterator(storeKey string, version uint64, start, end []byte) (corestore.Iterator, error)
+	ReverseIterator(storeKey string, version uint64, start, end []byte) (corestore.Iterator, error)
 
 	ApplyChangeset(version uint64, cs *Changeset) error
 

store/go.mod

@@ -68,3 +68,5 @@ require (
 	gopkg.in/yaml.v3 v3.0.1 // indirect
 	gotest.tools/v3 v3.5.1 // indirect
 )
+
+replace cosmossdk.io/core => ../core

store/iterator.go

@@ -1,38 +0,0 @@
-package store
-
-// Iterator defines an interface for iterating over a domain of key/value pairs.
-type Iterator interface {
-	// Domain returns the start (inclusive) and end (exclusive) limits of the iterator.
-	Domain() ([]byte, []byte)
-
-	// Valid returns if the iterator is currently valid.
-	Valid() bool
-
-	// Error returns any accumulated error. Error() should be called after all
-	// key/value pairs have been exhausted, i.e. after Next() has returned false.
-	Error() error
-
-	// Key returns the key of the current key/value pair, or nil if done.
-	Key() []byte
-
-	// Value returns the value of the current key/value pair, or nil if done.
-	Value() []byte
-
-	// Next moves the iterator to the next key/value pair.
-	Next() bool
-
-	// Close releases associated resources. It should NOT be idempotent. It must
-	// only be called once and any call after may panic.
-	Close()
-}
-
-// IteratorCreator defines an interface for creating forward and reverse iterators.
-type IteratorCreator interface {
-	// Iterator creates a new iterator for the given store name and domain, where
-	// domain is defined by [start, end). Note, both start and end are optional.
-	Iterator(storeKey string, start, end []byte) (Iterator, error)
-	// ReverseIterator creates a new reverse iterator for the given store name
-	// and domain, where domain is defined by [start, end). Note, both start and
-	// end are optional.
-	ReverseIterator(storeKey string, start, end []byte) (Iterator, error)
-}

store/kv/branch/iterator.go

@@ -3,10 +3,11 @@ package branch
 import (
 	"slices"
 
+	corestore "cosmossdk.io/core/store"
 	"cosmossdk.io/store/v2"
 )
 
-var _ store.Iterator = (*iterator)(nil)
+var _ corestore.Iterator = (*iterator)(nil)
 
 // iterator walks over both the KVStore's changeset, i.e. dirty writes, and the
 // parent iterator, which can either be another KVStore or the SS backend, at the
@@ -16,7 +17,7 @@ var _ store.Iterator = (*iterator)(nil)
 // iterator. This is because when an iterator is created, it takes a current
 // snapshot of the changeset.
 type iterator struct {
-	parentItr store.Iterator
+	parentItr corestore.Iterator
 	start     []byte
 	end       []byte
 	key       []byte
@@ -41,21 +42,21 @@ func (itr *iterator) Value() []byte {
 	return slices.Clone(itr.value)
 }
 
-func (itr *iterator) Close() {
+func (itr *iterator) Close() error {
 	itr.key = nil
 	itr.value = nil
 	itr.keys = nil
 	itr.values = nil
-	itr.parentItr.Close()
+	return itr.parentItr.Close()
 }
 
-func (itr *iterator) Next() bool {
+func (itr *iterator) Next() {
 	for {
 		switch {
 		case itr.exhausted && len(itr.keys) == 0: // exhausted both
 			itr.key = nil
 			itr.value = nil
-			return false
+			return
 
 		case itr.exhausted: // exhausted parent iterator but not store (dirty writes) iterator
 			nextKey := itr.keys[0]
@@ -72,15 +73,17 @@ func (itr *iterator) Next() bool {
 			if nextValue.Value != nil {
 				itr.key = []byte(nextKey)
 				itr.value = nextValue.Value
-				return true
+				return
 			}
 
 		case len(itr.keys) == 0: // exhausted store (dirty writes) iterator but not parent iterator
 			itr.key = itr.parentItr.Key()
 			itr.value = itr.parentItr.Value()
-			itr.exhausted = !itr.parentItr.Next()
 
-			return true
+			itr.parentItr.Next()
+			itr.exhausted = !itr.parentItr.Valid()
+
+			return
 
 		default: // parent iterator is not exhausted and we have store (dirty writes) remaining
 			dirtyKey := itr.keys[0]
@@ -102,14 +105,17 @@ func (itr *iterator) Next() bool {
 				if dirtyVal.Value != nil {
 					itr.key = []byte(dirtyKey)
 					itr.value = dirtyVal.Value
-					return true
+					return
 				}
 
 			case (!itr.reverse && parentKeyStr < dirtyKey) || (itr.reverse && parentKeyStr > dirtyKey): // parent's key should come before dirty key
 				itr.key = parentKey
 				itr.value = itr.parentItr.Value()
-				itr.exhausted = !itr.parentItr.Next()
-				return true
+
+				itr.parentItr.Next()
+				itr.exhausted = !itr.parentItr.Valid()
+
+				return
 
 			default:
 				// pop off key
@@ -120,12 +126,13 @@ func (itr *iterator) Next() bool {
 				itr.values[0].Value = nil
 				itr.values = itr.values[1:]
 
-				itr.exhausted = !itr.parentItr.Next()
+				itr.parentItr.Next()
+				itr.exhausted = !itr.parentItr.Valid()
 
 				if dirtyVal.Value != nil {
 					itr.key = []byte(dirtyKey)
 					itr.value = dirtyVal.Value
-					return true
+					return
 				}
 			}
 		}

store/kv/branch/store.go

@@ -8,6 +8,7 @@ import (
 
 	"golang.org/x/exp/maps"
 
+	corestore "cosmossdk.io/core/store"
 	"cosmossdk.io/store/v2"
 	"cosmossdk.io/store/v2/kv/trace"
 )
@@ -212,11 +213,11 @@ func (s *Store) Write() {
 // Note, writes that happen on the KVStore over an iterator will not affect the
 // iterator. This is because when an iterator is created, it takes a current
 // snapshot of the changeset.
-func (s *Store) Iterator(start, end []byte) store.Iterator {
+func (s *Store) Iterator(start, end []byte) corestore.Iterator {
 	s.mu.Lock()
 	defer s.mu.Unlock()
 
-	var parentItr store.Iterator
+	var parentItr corestore.Iterator
 	if s.parent != nil {
 		parentItr = s.parent.Iterator(start, end)
 	} else {
@@ -238,11 +239,11 @@ func (s *Store) Iterator(start, end []byte) store.Iterator {
 // Note, writes that happen on the KVStore over an iterator will not affect the
 // iterator. This is because when an iterator is created, it takes a current
 // snapshot of the changeset.
-func (s *Store) ReverseIterator(start, end []byte) store.Iterator {
+func (s *Store) ReverseIterator(start, end []byte) corestore.Iterator {
 	s.mu.Lock()
 	defer s.mu.Unlock()
 
-	var parentItr store.Iterator
+	var parentItr corestore.Iterator
 	if s.parent != nil {
 		parentItr = s.parent.ReverseIterator(start, end)
 	} else {
@@ -256,7 +257,7 @@ func (s *Store) ReverseIterator(start, end []byte) store.Iterator {
 	return s.newIterator(parentItr, start, end, true)
 }
 
-func (s *Store) newIterator(parentItr store.Iterator, start, end []byte, reverse bool) *iterator {
+func (s *Store) newIterator(parentItr corestore.Iterator, start, end []byte, reverse bool) *iterator {
 	startStr := string(start)
 	endStr := string(end)
 
@@ -305,7 +306,7 @@ func (s *Store) newIterator(parentItr store.Iterator, start, end []byte, reverse
 	}
 
 	// call Next() to move the iterator to the first key/value entry
-	_ = itr.Next()
+	itr.Next()
 
 	return itr
 }

store/kv/branch/store_test.go

@@ -157,7 +157,6 @@ func (s *StoreTestSuite) TestIterator_NoWrites() {
 		s.Require().NoError(itr.Error())
 
 		// seek past domain, which should make the iterator invalid and produce an error
-		s.Require().False(itr.Next())
 		s.Require().False(itr.Valid())
 	})
 
@@ -178,7 +177,6 @@ func (s *StoreTestSuite) TestIterator_NoWrites() {
 		s.Require().NoError(itr.Error())
 
 		// seek past domain, which should make the iterator invalid and produce an error
-		s.Require().False(itr.Next())
 		s.Require().False(itr.Valid())
 	})
 
@@ -199,7 +197,6 @@ func (s *StoreTestSuite) TestIterator_NoWrites() {
 		s.Require().NoError(itr.Error())
 
 		// seek past domain, which should make the iterator invalid and produce an error
-		s.Require().False(itr.Next())
 		s.Require().False(itr.Valid())
 	})
 
@@ -220,7 +217,6 @@ func (s *StoreTestSuite) TestIterator_NoWrites() {
 		s.Require().NoError(itr.Error())
 
 		// seek past domain, which should make the iterator invalid and produce an error
-		s.Require().False(itr.Next())
 		s.Require().False(itr.Valid())
 	})
 }
@@ -264,7 +260,6 @@ func (s *StoreTestSuite) TestIterator_DirtyWrites() {
 		s.Require().NoError(itr.Error())
 
 		// seek past domain, which should make the iterator invalid and produce an error
-		s.Require().False(itr.Next())
 		s.Require().False(itr.Valid())
 	})
 
@@ -290,7 +285,6 @@ func (s *StoreTestSuite) TestIterator_DirtyWrites() {
 		s.Require().NoError(itr.Error())
 
 		// seek past domain, which should make the iterator invalid and produce an error
-		s.Require().False(itr.Next())
 		s.Require().False(itr.Valid())
 	})
 
@@ -316,7 +310,6 @@ func (s *StoreTestSuite) TestIterator_DirtyWrites() {
 		s.Require().NoError(itr.Error())
 
 		// seek past domain, which should make the iterator invalid and produce an error
-		s.Require().False(itr.Next())
 		s.Require().False(itr.Valid())
 	})
 
@@ -342,7 +335,6 @@ func (s *StoreTestSuite) TestIterator_DirtyWrites() {
 		s.Require().NoError(itr.Error())
 
 		// seek past domain, which should make the iterator invalid and produce an error
-		s.Require().False(itr.Next())
 		s.Require().False(itr.Valid())
 	})
 }
@@ -366,7 +358,6 @@ func (s *StoreTestSuite) TestReverseIterator_NoWrites() {
 		s.Require().NoError(itr.Error())
 
 		// seek past domain, which should make the iterator invalid and produce an error
-		s.Require().False(itr.Next())
 		s.Require().False(itr.Valid())
 	})
 
@@ -388,7 +379,6 @@ func (s *StoreTestSuite) TestReverseIterator_NoWrites() {
 		s.Require().NoError(itr.Error())
 
 		// seek past domain, which should make the iterator invalid and produce an error
-		s.Require().False(itr.Next())
 		s.Require().False(itr.Valid())
 	})
 
@@ -410,7 +400,6 @@ func (s *StoreTestSuite) TestReverseIterator_NoWrites() {
 		s.Require().NoError(itr.Error())
 
 		// seek past domain, which should make the iterator invalid and produce an error
-		s.Require().False(itr.Next())
 		s.Require().False(itr.Valid())
 	})
 
@@ -432,7 +421,6 @@ func (s *StoreTestSuite) TestReverseIterator_NoWrites() {
 		s.Require().NoError(itr.Error())
 
 		// seek past domain, which should make the iterator invalid and produce an error
-		s.Require().False(itr.Next())
 		s.Require().False(itr.Valid())
 	})
 }
@@ -477,7 +465,6 @@ func (s *StoreTestSuite) TestReverseIterator_DirtyWrites() {
 		s.Require().NoError(itr.Error())
 
 		// seek past domain, which should make the iterator invalid and produce an error
-		s.Require().False(itr.Next())
 		s.Require().False(itr.Valid())
 	})
 
@@ -504,7 +491,6 @@ func (s *StoreTestSuite) TestReverseIterator_DirtyWrites() {
 		s.Require().NoError(itr.Error())
 
 		// seek past domain, which should make the iterator invalid and produce an error
-		s.Require().False(itr.Next())
 		s.Require().False(itr.Valid())
 	})
 
@@ -531,7 +517,6 @@ func (s *StoreTestSuite) TestReverseIterator_DirtyWrites() {
 		s.Require().NoError(itr.Error())
 
 		// seek past domain, which should make the iterator invalid and produce an error
-		s.Require().False(itr.Next())
 		s.Require().False(itr.Valid())
 	})
 
@@ -558,7 +543,6 @@ func (s *StoreTestSuite) TestReverseIterator_DirtyWrites() {
 		s.Require().NoError(itr.Error())
 
 		// seek past domain, which should make the iterator invalid and produce an error
-		s.Require().False(itr.Next())
 		s.Require().False(itr.Valid())
 	})
 }

store/kv/mem/iterator.go

@@ -6,10 +6,11 @@ import (
 	"github.com/tidwall/btree"
 	"golang.org/x/exp/slices"
 
+	corestore "cosmossdk.io/core/store"
 	"cosmossdk.io/store/v2"
 )
 
-var _ store.Iterator = (*iterator)(nil)
+var _ corestore.Iterator = (*iterator)(nil)
 
 type iterator struct {
 	treeItr btree.IterG[store.KVPair]
@@ -19,7 +20,7 @@ type iterator struct {
 	valid   bool
 }
 
-func newIterator(tree *btree.BTreeG[store.KVPair], start, end []byte, reverse bool) store.Iterator {
+func newIterator(tree *btree.BTreeG[store.KVPair], start, end []byte, reverse bool) corestore.Iterator {
 	if (start != nil && len(start) == 0) || (end != nil && len(end) == 0) {
 		panic(store.ErrKeyEmpty)
 	}
@@ -83,9 +84,9 @@ func (itr *iterator) Value() []byte {
 	return slices.Clone(itr.treeItr.Item().Value)
 }
 
-func (itr *iterator) Next() bool {
+func (itr *iterator) Next() {
 	if !itr.valid {
-		return false
+		return
 	}
 
 	if !itr.reverse {
@@ -98,11 +99,12 @@ func (itr *iterator) Next() bool {
 		itr.valid = itr.keyInRange(itr.Key())
 	}
 
-	return itr.valid
+	return
 }
 
-func (itr *iterator) Close() {
+func (itr *iterator) Close() error {
 	itr.treeItr.Release()
+	return nil
 }
 
 func (itr *iterator) Error() error {

store/kv/mem/store.go

@@ -5,6 +5,7 @@ import (
 
 	"github.com/tidwall/btree"
 
+	corestore "cosmossdk.io/core/store"
 	"cosmossdk.io/store/v2"
 )
 
@@ -92,10 +93,10 @@ func (s *Store) Reset(_ uint64) error {
 	return nil
 }
 
-func (s *Store) Iterator(start, end []byte) store.Iterator {
+func (s *Store) Iterator(start, end []byte) corestore.Iterator {
 	return newIterator(s.tree, start, end, false)
 }
 
-func (s *Store) ReverseIterator(start, end []byte) store.Iterator {
+func (s *Store) ReverseIterator(start, end []byte) corestore.Iterator {
 	return newIterator(s.tree, start, end, true)
 }

store/kv/mem/store_test.go

@@ -92,7 +92,6 @@ func (s *StoreTestSuite) TestIterator() {
 		s.Require().NoError(itr.Error())
 
 		// seek past domain, which should make the iterator invalid and produce an error
-		s.Require().False(itr.Next())
 		s.Require().False(itr.Valid())
 	})
 
@@ -113,7 +112,6 @@ func (s *StoreTestSuite) TestIterator() {
 		s.Require().NoError(itr.Error())
 
 		// seek past domain, which should make the iterator invalid and produce an error
-		s.Require().False(itr.Next())
 		s.Require().False(itr.Valid())
 	})
 
@@ -134,7 +132,7 @@ func (s *StoreTestSuite) TestIterator() {
 		s.Require().NoError(itr.Error())
 
 		// seek past domain, which should make the iterator invalid and produce an error
-		s.Require().False(itr.Next())
+
 		s.Require().False(itr.Valid())
 	})
 
@@ -155,7 +153,6 @@ func (s *StoreTestSuite) TestIterator() {
 		s.Require().NoError(itr.Error())
 
 		// seek past domain, which should make the iterator invalid and produce an error
-		s.Require().False(itr.Next())
 		s.Require().False(itr.Valid())
 	})
 }
@@ -185,7 +182,6 @@ func (s *StoreTestSuite) TestReverseIterator() {
 		s.Require().NoError(itr.Error())
 
 		// seek past domain, which should make the iterator invalid and produce an error
-		s.Require().False(itr.Next())
 		s.Require().False(itr.Valid())
 	})
 
@@ -208,7 +204,6 @@ func (s *StoreTestSuite) TestReverseIterator() {
 
 		// seek past domain, which should make the iterator invalid and produce an error
 		s.Require().False(itr.Valid())
-		s.Require().False(itr.Next())
 	})
 
 	// reverse iterator with with a start and end domain
@@ -229,7 +224,6 @@ func (s *StoreTestSuite) TestReverseIterator() {
 		s.Require().NoError(itr.Error())
 
 		// seek past domain, which should make the iterator invalid and produce an error
-		s.Require().False(itr.Next())
 		s.Require().False(itr.Valid())
 	})
 
@@ -251,7 +245,6 @@ func (s *StoreTestSuite) TestReverseIterator() {
 		s.Require().NoError(itr.Error())
 
 		// seek past domain, which should make the iterator invalid and produce an error
-		s.Require().False(itr.Next())
 		s.Require().False(itr.Valid())
 	})
 }

store/kv/trace/iterator.go

@@ -3,18 +3,19 @@ package trace
 import (
 	"io"
 
+	corestore "cosmossdk.io/core/store"
 	"cosmossdk.io/store/v2"
 )
 
-var _ store.Iterator = (*iterator)(nil)
+var _ corestore.Iterator = (*iterator)(nil)
 
 type iterator struct {
-	parent  store.Iterator
+	parent  corestore.Iterator
 	writer  io.Writer
 	context store.TraceContext
 }
 
-func newIterator(w io.Writer, parent store.Iterator, tc store.TraceContext) store.Iterator {
+func newIterator(w io.Writer, parent corestore.Iterator, tc store.TraceContext) corestore.Iterator {
 	return &iterator{
 		parent:  parent,
 		writer:  w,
@@ -30,16 +31,16 @@ func (itr *iterator) Valid() bool {
 	return itr.parent.Valid()
 }
 
-func (itr *iterator) Next() bool {
-	return itr.parent.Next()
+func (itr *iterator) Next() {
+	itr.parent.Next()
 }
 
 func (itr *iterator) Error() error {
 	return itr.parent.Error()
 }
 
-func (itr *iterator) Close() {
-	itr.parent.Close()
+func (itr *iterator) Close() error {
+	return itr.parent.Close()
 }
 
 func (itr *iterator) Key() []byte {

store/kv/trace/store.go

@@ -8,6 +8,7 @@ import (
 
 	"github.com/cockroachdb/errors"
 
+	corestore "cosmossdk.io/core/store"
 	"cosmossdk.io/store/v2"
 )
 
@@ -98,11 +99,11 @@ func (s *Store) BranchWithTrace(_ io.Writer, _ store.TraceContext) store.Branche
 	panic(fmt.Sprintf("cannot call BranchWithTrace() on %T", s))
 }
 
-func (s *Store) Iterator(start, end []byte) store.Iterator {
+func (s *Store) Iterator(start, end []byte) corestore.Iterator {
 	return newIterator(s.writer, s.parent.Iterator(start, end), s.context)
 }
 
-func (s *Store) ReverseIterator(start, end []byte) store.Iterator {
+func (s *Store) ReverseIterator(start, end []byte) corestore.Iterator {
 	return newIterator(s.writer, s.parent.ReverseIterator(start, end), s.context)
 }
 

store/kv/trace/store_test.go

@@ -203,7 +203,6 @@ func TestTestTraceKVStoreIterator(t *testing.T) {
 	}
 
 	require.False(t, iterator.Valid())
-	require.False(t, iterator.Next())
 }
 
 func TestTestTraceKVStoreReverseIterator(t *testing.T) {
@@ -258,7 +257,6 @@ func TestTestTraceKVStoreReverseIterator(t *testing.T) {
 	}
 
 	require.False(t, iterator.Valid())
-	require.False(t, iterator.Next())
 }
 
 func TestTraceKVStoreGetStoreType(t *testing.T) {

store/storage/database.go

@@ -3,6 +3,7 @@ package storage
 import (
 	"io"
 
+	corestore "cosmossdk.io/core/store"
 	"cosmossdk.io/store/v2"
 )
 
@@ -16,8 +17,8 @@ type Database interface {
 	GetLatestVersion() (uint64, error)
 	SetLatestVersion(version uint64) error
 
-	Iterator(storeKey string, version uint64, start, end []byte) (store.Iterator, error)
-	ReverseIterator(storeKey string, version uint64, start, end []byte) (store.Iterator, error)
+	Iterator(storeKey string, version uint64, start, end []byte) (corestore.Iterator, error)
+	ReverseIterator(storeKey string, version uint64, start, end []byte) (corestore.Iterator, error)
 
 	Prune(version uint64) error
 

store/storage/pebbledb/db.go

@@ -10,6 +10,7 @@ import (
 
 	"github.com/cockroachdb/pebble"
 
+	corestore "cosmossdk.io/core/store"
 	"cosmossdk.io/store/v2"
 	"cosmossdk.io/store/v2/storage"
 )
@@ -262,7 +263,7 @@ func (db *Database) Prune(version uint64) error {
 	return db.setPruneHeight(version)
 }
 
-func (db *Database) Iterator(storeKey string, version uint64, start, end []byte) (store.Iterator, error) {
+func (db *Database) Iterator(storeKey string, version uint64, start, end []byte) (corestore.Iterator, error) {
 	if (start != nil && len(start) == 0) || (end != nil && len(end) == 0) {
 		return nil, store.ErrKeyEmpty
 	}
@@ -283,7 +284,7 @@ func (db *Database) Iterator(storeKey string, version uint64, start, end []byte)
 	return newPebbleDBIterator(itr, storePrefix(storeKey), start, end, version, db.earliestVersion, false), nil
 }
 
-func (db *Database) ReverseIterator(storeKey string, version uint64, start, end []byte) (store.Iterator, error) {
+func (db *Database) ReverseIterator(storeKey string, version uint64, start, end []byte) (corestore.Iterator, error) {
 	if (start != nil && len(start) == 0) || (end != nil && len(end) == 0) {
 		return nil, store.ErrKeyEmpty
 	}

store/storage/pebbledb/iterator.go

@@ -7,20 +7,17 @@ import (
 
 	"github.com/cockroachdb/pebble"
 
-	"cosmossdk.io/store/v2"
+	corestore "cosmossdk.io/core/store"
 )
 
-var _ store.Iterator = (*iterator)(nil)
+var _ corestore.Iterator = (*iterator)(nil)
 
 // iterator implements the store.Iterator interface. It wraps a PebbleDB iterator
 // with added MVCC key handling logic. The iterator will iterate over the key space
 // in the provided domain for a given version. If a key has been written at the
 // provided version, that key/value pair will be iterated over. Otherwise, the
 // latest version for that key/value pair will be iterated over s.t. it's less
-// than the provided version. Note:
-//
-// - The start key must not be empty.
-// - Currently, reverse iteration is NOT supported.
+// than the provided version.
 type iterator struct {
 	source             *pebble.Iterator
 	prefix, start, end []byte
@@ -76,7 +73,7 @@ func newPebbleDBIterator(src *pebble.Iterator, prefix, mvccStart, mvccEnd []byte
 	// The cursor might now be pointing at a key/value pair that is tombstoned.
 	// If so, we must move the cursor.
 	if itr.valid && itr.cursorTombstoned() {
-		itr.valid = itr.Next()
+		itr.Next()
 	}
 
 	return itr
@@ -115,7 +112,7 @@ func (itr *iterator) Value() []byte {
 	return slices.Clone(val)
 }
 
-func (itr *iterator) Next() bool {
+func (itr *iterator) Next() {
 	var next bool
 	if itr.reverse {
 		currKey, _, ok := SplitMVCCKey(itr.source.Key())
@@ -142,12 +139,12 @@ func (itr *iterator) Next() bool {
 			// XXX: This should not happen as that would indicate we have a malformed
 			// MVCC key.
 			itr.valid = false
-			return itr.valid
+			return
 		}
 		if !bytes.HasPrefix(nextKey, itr.prefix) {
 			// the next key must have itr.prefix as the prefix
 			itr.valid = false
-			return itr.valid
+			return
 		}
 
 		// Move the iterator to the closest version to the desired version, so we
@@ -157,14 +154,14 @@ func (itr *iterator) Next() bool {
 		// The cursor might now be pointing at a key/value pair that is tombstoned.
 		// If so, we must move the cursor.
 		if itr.valid && itr.cursorTombstoned() {
-			itr.valid = itr.Next()
+			itr.Next()
 		}
 
-		return itr.valid
+		return
 	}
 
 	itr.valid = false
-	return itr.valid
+	return
 }
 
 func (itr *iterator) Valid() bool {
@@ -195,10 +192,12 @@ func (itr *iterator) Error() error {
 	return itr.source.Error()
 }
 
-func (itr *iterator) Close() {
-	_ = itr.source.Close()
+func (itr *iterator) Close() error {
+	err := itr.source.Close()
 	itr.source = nil
 	itr.valid = false
+
+	return err
 }
 
 func (itr *iterator) assertIsValid() {

store/storage/rocksdb/db.go

@@ -11,6 +11,7 @@ import (
 	"github.com/linxGnu/grocksdb"
 	"golang.org/x/exp/slices"
 
+	corestore "cosmossdk.io/core/store"
 	"cosmossdk.io/store/v2"
 	"cosmossdk.io/store/v2/storage"
 	"cosmossdk.io/store/v2/storage/util"
@@ -162,7 +163,7 @@ func (db *Database) Prune(version uint64) error {
 	return nil
 }
 
-func (db *Database) Iterator(storeKey string, version uint64, start, end []byte) (store.Iterator, error) {
+func (db *Database) Iterator(storeKey string, version uint64, start, end []byte) (corestore.Iterator, error) {
 	if (start != nil && len(start) == 0) || (end != nil && len(end) == 0) {
 		return nil, store.ErrKeyEmpty
 	}
@@ -178,7 +179,7 @@ func (db *Database) Iterator(storeKey string, version uint64, start, end []byte)
 	return newRocksDBIterator(itr, prefix, start, end, false), nil
 }
 
-func (db *Database) ReverseIterator(storeKey string, version uint64, start, end []byte) (store.Iterator, error) {
+func (db *Database) ReverseIterator(storeKey string, version uint64, start, end []byte) (corestore.Iterator, error) {
 	if (start != nil && len(start) == 0) || (end != nil && len(end) == 0) {
 		return nil, store.ErrKeyEmpty
 	}

store/storage/rocksdb/db_test.go

@@ -62,7 +62,6 @@ func TestDatabase_ReverseIterator(t *testing.T) {
 	require.NoError(t, iter.Error())
 
 	// seek past domain, which should make the iterator invalid and produce an error
-	require.False(t, iter.Next())
 	require.False(t, iter.Valid())
 
 	// reverse iterator with with a start and end domain
@@ -83,7 +82,6 @@ func TestDatabase_ReverseIterator(t *testing.T) {
 	require.NoError(t, iter2.Error())
 
 	// seek past domain, which should make the iterator invalid and produce an error
-	require.False(t, iter2.Next())
 	require.False(t, iter2.Valid())
 
 	// start must be <= end

store/storage/rocksdb/iterator.go

@@ -8,10 +8,10 @@ import (
 
 	"github.com/linxGnu/grocksdb"
 
-	"cosmossdk.io/store/v2"
+	corestore "cosmossdk.io/core/store"
 )
 
-var _ store.Iterator = (*iterator)(nil)
+var _ corestore.Iterator = (*iterator)(nil)
 
 type iterator struct {
 	source             *grocksdb.Iterator
@@ -124,9 +124,9 @@ func (itr *iterator) Value() []byte {
 	return copyAndFreeSlice(itr.source.Value())
 }
 
-func (itr iterator) Next() bool {
+func (itr iterator) Next() {
 	if itr.invalid {
-		return false
+		return
 	}
 
 	if itr.reverse {
@@ -135,17 +135,19 @@ func (itr iterator) Next() bool {
 		itr.source.Next()
 	}
 
-	return itr.Valid()
+	return
 }
 
 func (itr *iterator) Error() error {
 	return itr.source.Err()
 }
 
-func (itr *iterator) Close() {
+func (itr *iterator) Close() error {
 	itr.source.Close()
 	itr.source = nil
 	itr.invalid = true
+
+	return nil
 }
 
 func (itr *iterator) assertIsValid() {

store/storage/sqlite/db.go

@@ -10,6 +10,7 @@ import (
 
 	_ "github.com/mattn/go-sqlite3"
 
+	corestore "cosmossdk.io/core/store"
 	"cosmossdk.io/store/v2"
 	"cosmossdk.io/store/v2/storage"
 )
@@ -59,7 +60,7 @@ func New(dataDir string) (*Database, error) {
 
 	stmt := `
 	CREATE TABLE IF NOT EXISTS state_storage (
-		id integer not null primary key, 
+		id integer not null primary key,
 		store_key varchar not null,
 		key varchar not null,
 		value varchar not null,
@@ -214,7 +215,7 @@ func (db *Database) Prune(version uint64) error {
 	return nil
 }
 
-func (db *Database) Iterator(storeKey string, version uint64, start, end []byte) (store.Iterator, error) {
+func (db *Database) Iterator(storeKey string, version uint64, start, end []byte) (corestore.Iterator, error) {
 	if (start != nil && len(start) == 0) || (end != nil && len(end) == 0) {
 		return nil, store.ErrKeyEmpty
 	}
@@ -226,7 +227,7 @@ func (db *Database) Iterator(storeKey string, version uint64, start, end []byte)
 	return newIterator(db, storeKey, version, start, end, false)
 }
 
-func (db *Database) ReverseIterator(storeKey string, version uint64, start, end []byte) (store.Iterator, error) {
+func (db *Database) ReverseIterator(storeKey string, version uint64, start, end []byte) (corestore.Iterator, error) {
 	if (start != nil && len(start) == 0) || (end != nil && len(end) == 0) {
 		return nil, store.ErrKeyEmpty
 	}

store/storage/sqlite/db_test.go

@@ -61,7 +61,6 @@ func TestDatabase_ReverseIterator(t *testing.T) {
 	require.NoError(t, iter.Error())
 
 	// seek past domain, which should make the iterator invalid and produce an error
-	require.False(t, iter.Next())
 	require.False(t, iter.Valid())
 
 	// reverse iterator with with a start and end domain
@@ -82,7 +81,6 @@ func TestDatabase_ReverseIterator(t *testing.T) {
 	require.NoError(t, iter2.Error())
 
 	// seek past domain, which should make the iterator invalid and produce an error
-	require.False(t, iter2.Next())
 	require.False(t, iter2.Valid())
 
 	// start must be <= end

store/storage/sqlite/iterator.go

@@ -8,10 +8,10 @@ import (
 
 	"golang.org/x/exp/slices"
 
-	"cosmossdk.io/store/v2"
+	corestore "cosmossdk.io/core/store"
 )
 
-var _ store.Iterator = (*iterator)(nil)
+var _ corestore.Iterator = (*iterator)(nil)
 
 type iterator struct {
 	statement  *sql.Stmt
@@ -100,14 +100,16 @@ func newIterator(db *Database, storeKey string, targetVersion uint64, start, end
 	return itr, nil
 }
 
-func (itr *iterator) Close() {
+func (itr *iterator) Close() (err error) {
 	if itr.statement != nil {
-		_ = itr.statement.Close()
+		err = itr.statement.Close()
 	}
 
 	itr.valid = false
 	itr.statement = nil
 	itr.rows = nil
+
+	return err
 }
 
 // Domain returns the domain of the iterator. The caller must not modify the
@@ -143,14 +145,14 @@ func (itr *iterator) Valid() bool {
 	return true
 }
 
-func (itr *iterator) Next() bool {
+func (itr *iterator) Next() {
 	if itr.rows.Next() {
 		itr.parseRow()
-		return itr.Valid()
+		return
 	}
 
 	itr.valid = false
-	return itr.valid
+	return
 }
 
 func (itr *iterator) Error() error {

store/storage/storage_test_suite.go

@@ -265,7 +265,6 @@ func (s *StorageTestSuite) TestDatabase_Iterator() {
 		s.Require().NoError(itr.Error())
 
 		// seek past domain, which should make the iterator invalid and produce an error
-		s.Require().False(itr.Next())
 		s.Require().False(itr.Valid())
 	}
 
@@ -288,7 +287,6 @@ func (s *StorageTestSuite) TestDatabase_Iterator() {
 		s.Require().NoError(itr2.Error())
 
 		// seek past domain, which should make the iterator invalid and produce an error
-		s.Require().False(itr2.Next())
 		s.Require().False(itr2.Valid())
 	}
 

store/storage/store.go

@@ -3,6 +3,7 @@ package storage
 import (
 	"fmt"
 
+	corestore "cosmossdk.io/core/store"
 	"cosmossdk.io/store/v2"
 	"cosmossdk.io/store/v2/snapshots"
 )
@@ -74,12 +75,12 @@ func (ss *StorageStore) SetLatestVersion(version uint64) error {
 }
 
 // Iterator returns an iterator over the specified domain and prefix.
-func (ss *StorageStore) Iterator(storeKey string, version uint64, start, end []byte) (store.Iterator, error) {
+func (ss *StorageStore) Iterator(storeKey string, version uint64, start, end []byte) (corestore.Iterator, error) {
 	return ss.db.Iterator(storeKey, version, start, end)
 }
 
 // ReverseIterator returns an iterator over the specified domain and prefix in reverse.
-func (ss *StorageStore) ReverseIterator(storeKey string, version uint64, start, end []byte) (store.Iterator, error) {
+func (ss *StorageStore) ReverseIterator(storeKey string, version uint64, start, end []byte) (corestore.Iterator, error) {
 	return ss.db.ReverseIterator(storeKey, version, start, end)
 }
 

store/store.go

@@ -4,6 +4,7 @@ import (
 	"io"
 
 	coreheader "cosmossdk.io/core/header"
+	corestore "cosmossdk.io/core/store"
 	"cosmossdk.io/store/v2/metrics"
 )
 
@@ -148,11 +149,11 @@ type KVStore interface {
 	//
 	// CONTRACT: No writes may happen within a domain while an iterator exists over
 	// it, with the exception of a branched/cached KVStore.
-	Iterator(start, end []byte) Iterator
+	Iterator(start, end []byte) corestore.Iterator
 
 	// ReverseIterator creates a new reverse Iterator over the domain [start, end).
 	// It has the some properties and contracts as Iterator.
-	ReverseIterator(start, end []byte) Iterator
+	ReverseIterator(start, end []byte) corestore.Iterator
 }
 
 // BranchedKVStore defines an interface for a branched a KVStore. It extends KVStore