From 56f28145dd19105a023fd54d6a7f24c3181fae95 Mon Sep 17 00:00:00 2001
From: Sunny Aggarwal <sunnya97@gmail.com>
Date: Fri, 30 Mar 2018 22:36:04 +0200
Subject: [PATCH 1/9] working on it

---
 Gopkg.lock              |  2 +-
 store/iavlstore.go      | 19 ++++++++++++++-
 store/iavlstore_test.go | 52 +++++++++++++++++++++++++++++++++++++++--
 3 files changed, 69 insertions(+), 4 deletions(-)

diff --git a/Gopkg.lock b/Gopkg.lock
index 267acf32b..377390297 100644
--- a/Gopkg.lock
+++ b/Gopkg.lock
@@ -458,6 +458,6 @@
 [solve-meta]
   analyzer-name = "dep"
   analyzer-version = 1
-  inputs-digest = "cce90fda84a63ae5b41b40f0edc357eec4020d17fdd61585960ad537418749ea"
+  inputs-digest = "ed1f3f7f1728cd02945f90ca780e9bdc982573a36a5cc8d7e9f19fb40ba2ca19"
   solver-name = "gps-cdcl"
   solver-version = 1
diff --git a/store/iavlstore.go b/store/iavlstore.go
index 96110c59c..5f1917e2c 100644
--- a/store/iavlstore.go
+++ b/store/iavlstore.go
@@ -122,7 +122,24 @@ func (st *iavlStore) Iterator(start, end []byte) Iterator {
 func (st *iavlStore) Subspace(prefix []byte) Iterator {
 	end := make([]byte, len(prefix))
 	copy(end, prefix)
-	end[len(end)-1]++
+	finished := false
+	i := 1
+
+	for !finished {
+		fmt.Printf("%v %v \n", len(end), i)
+		fmt.Printf("%v \n", end)
+		if end[len(end)-i] != byte(255) {
+			end[len(end)-i]++
+			finished = true
+		} else {
+			end[len(end)-i]++
+			i++
+			if i > len(end) {
+				end = []byte{}
+				finished = true
+			}
+		}
+	}
 	return st.Iterator(prefix, end)
 }
 
diff --git a/store/iavlstore_test.go b/store/iavlstore_test.go
index 7adae625e..85e02ba25 100644
--- a/store/iavlstore_test.go
+++ b/store/iavlstore_test.go
@@ -73,13 +73,26 @@ func TestIAVLIterator(t *testing.T) {
 	iavlStore := newIAVLStore(tree, numHistory)
 	iter := iavlStore.Iterator([]byte("aloha"), []byte("hellz"))
 	expected := []string{"aloha", "hello"}
-	for i := 0; iter.Valid(); iter.Next() {
+	i := 0
+	for i = 0; iter.Valid(); iter.Next() {
 		expectedKey := expected[i]
 		key, value := iter.Key(), iter.Value()
 		assert.EqualValues(t, key, expectedKey)
 		assert.EqualValues(t, value, treeData[expectedKey])
 		i += 1
 	}
+	assert.Equal(t, i, len(expected))
+
+	iter = iavlStore.Iterator([]byte("golang"), []byte("rocks"))
+	expected = []string{"hello"}
+	for i = 0; iter.Valid(); iter.Next() {
+		expectedKey := expected[i]
+		key, value := iter.Key(), iter.Value()
+		assert.EqualValues(t, key, expectedKey)
+		assert.EqualValues(t, value, treeData[expectedKey])
+		i += 1
+	}
+	assert.Equal(t, i, len(expected))
 }
 
 func TestIAVLSubspace(t *testing.T) {
@@ -90,16 +103,51 @@ func TestIAVLSubspace(t *testing.T) {
 	iavlStore.Set([]byte("test1"), []byte("test1"))
 	iavlStore.Set([]byte("test2"), []byte("test2"))
 	iavlStore.Set([]byte("test3"), []byte("test3"))
+	iavlStore.Set([]byte{byte(55), byte(255), byte(255), byte(0)}, []byte("test4"))
+	iavlStore.Set([]byte{byte(55), byte(255), byte(255), byte(1)}, []byte("test4"))
+	iavlStore.Set([]byte{byte(55), byte(255), byte(255), byte(255)}, []byte("test4"))
+	i := 0
 
 	iter := iavlStore.Subspace([]byte("test"))
 	expected := []string{"test1", "test2", "test3"}
-	for i := 0; iter.Valid(); iter.Next() {
+	for i = 0; iter.Valid(); iter.Next() {
 		expectedKey := expected[i]
 		key, value := iter.Key(), iter.Value()
 		assert.EqualValues(t, key, expectedKey)
 		assert.EqualValues(t, value, expectedKey)
 		i += 1
 	}
+	assert.Equal(t, i, len(expected))
+
+	iter = iavlStore.Subspace([]byte{byte(55), byte(255), byte(255)})
+	expected2 := [][]byte{
+		[]byte{byte(55), byte(255), byte(255), byte(0)},
+		[]byte{byte(55), byte(255), byte(255), byte(1)},
+		[]byte{byte(55), byte(255), byte(255), byte(255)},
+	}
+	for i = 0; iter.Valid(); iter.Next() {
+		expectedKey := expected2[i]
+		key, value := iter.Key(), iter.Value()
+		assert.EqualValues(t, key, expectedKey)
+		assert.EqualValues(t, value, []byte("test4"))
+		i += 1
+	}
+	assert.Equal(t, i, len(expected))
+
+	iter = iavlStore.Subspace([]byte{byte(255), byte(255)})
+	expected2 = [][]byte{
+		[]byte{byte(255), byte(255), byte(0)},
+		[]byte{byte(255), byte(255), byte(1)},
+		[]byte{byte(255), byte(255), byte(255)},
+	}
+	for i = 0; iter.Valid(); iter.Next() {
+		expectedKey := expected2[i]
+		key, value := iter.Key(), iter.Value()
+		assert.EqualValues(t, key, expectedKey)
+		assert.EqualValues(t, value, []byte("test4"))
+		i += 1
+	}
+	assert.Equal(t, i, len(expected))
 }
 
 func TestIAVLStoreQuery(t *testing.T) {

From 271d240897a6826074125eb29fd754692dad3984 Mon Sep 17 00:00:00 2001
From: Sunny Aggarwal <sunnya97@gmail.com>
Date: Sat, 31 Mar 2018 19:30:25 +0200
Subject: [PATCH 2/9] trying to figure it out

---
 store/iavlstore.go      |  6 +++---
 store/iavlstore_test.go | 21 ++++++++++++++++-----
 2 files changed, 19 insertions(+), 8 deletions(-)

diff --git a/store/iavlstore.go b/store/iavlstore.go
index 5f1917e2c..a1a48722c 100644
--- a/store/iavlstore.go
+++ b/store/iavlstore.go
@@ -126,8 +126,6 @@ func (st *iavlStore) Subspace(prefix []byte) Iterator {
 	i := 1
 
 	for !finished {
-		fmt.Printf("%v %v \n", len(end), i)
-		fmt.Printf("%v \n", end)
 		if end[len(end)-i] != byte(255) {
 			end[len(end)-i]++
 			finished = true
@@ -135,11 +133,12 @@ func (st *iavlStore) Subspace(prefix []byte) Iterator {
 			end[len(end)-i]++
 			i++
 			if i > len(end) {
-				end = []byte{}
+				end = nil
 				finished = true
 			}
 		}
 	}
+	fmt.Printf("%v \n", end)
 	return st.Iterator(prefix, end)
 }
 
@@ -243,6 +242,7 @@ func newIAVLIterator(tree *iavl.Tree, start, end []byte, ascending bool) *iavlIt
 		quitCh:    make(chan struct{}),
 		initCh:    make(chan struct{}),
 	}
+	fmt.Printf("%v   %v \n", iter.start, iter.end)
 	go iter.iterateRoutine()
 	go iter.initRoutine()
 	return iter
diff --git a/store/iavlstore_test.go b/store/iavlstore_test.go
index 85e02ba25..6e276c3d2 100644
--- a/store/iavlstore_test.go
+++ b/store/iavlstore_test.go
@@ -81,7 +81,7 @@ func TestIAVLIterator(t *testing.T) {
 		assert.EqualValues(t, value, treeData[expectedKey])
 		i += 1
 	}
-	assert.Equal(t, i, len(expected))
+	assert.Equal(t, len(expected), i)
 
 	iter = iavlStore.Iterator([]byte("golang"), []byte("rocks"))
 	expected = []string{"hello"}
@@ -92,7 +92,18 @@ func TestIAVLIterator(t *testing.T) {
 		assert.EqualValues(t, value, treeData[expectedKey])
 		i += 1
 	}
-	assert.Equal(t, i, len(expected))
+	assert.Equal(t, len(expected), i)
+
+	iter = iavlStore.Iterator([]byte("golang"), nil)
+	expected = []string{"hello"}
+	for i = 0; iter.Valid(); iter.Next() {
+		expectedKey := expected[i]
+		key, value := iter.Key(), iter.Value()
+		assert.EqualValues(t, key, expectedKey)
+		assert.EqualValues(t, value, treeData[expectedKey])
+		i += 1
+	}
+	assert.Equal(t, len(expected), i)
 }
 
 func TestIAVLSubspace(t *testing.T) {
@@ -117,7 +128,7 @@ func TestIAVLSubspace(t *testing.T) {
 		assert.EqualValues(t, value, expectedKey)
 		i += 1
 	}
-	assert.Equal(t, i, len(expected))
+	assert.Equal(t, len(expected), i)
 
 	iter = iavlStore.Subspace([]byte{byte(55), byte(255), byte(255)})
 	expected2 := [][]byte{
@@ -132,7 +143,7 @@ func TestIAVLSubspace(t *testing.T) {
 		assert.EqualValues(t, value, []byte("test4"))
 		i += 1
 	}
-	assert.Equal(t, i, len(expected))
+	assert.Equal(t, len(expected), i)
 
 	iter = iavlStore.Subspace([]byte{byte(255), byte(255)})
 	expected2 = [][]byte{
@@ -147,7 +158,7 @@ func TestIAVLSubspace(t *testing.T) {
 		assert.EqualValues(t, value, []byte("test4"))
 		i += 1
 	}
-	assert.Equal(t, i, len(expected))
+	assert.Equal(t, len(expected), i)
 }
 
 func TestIAVLStoreQuery(t *testing.T) {

From 3f1362f838c22fcb71ecfcb7217f27992e2b6c63 Mon Sep 17 00:00:00 2001
From: Sunny Aggarwal <sunnya97@gmail.com>
Date: Sun, 1 Apr 2018 00:02:29 +0200
Subject: [PATCH 3/9] why u no work

---
 store/iavlstore_test.go | 33 +++++++++++++++++++++++++++++++++
 1 file changed, 33 insertions(+)

diff --git a/store/iavlstore_test.go b/store/iavlstore_test.go
index 6e276c3d2..02b0d58bb 100644
--- a/store/iavlstore_test.go
+++ b/store/iavlstore_test.go
@@ -94,6 +94,39 @@ func TestIAVLIterator(t *testing.T) {
 	}
 	assert.Equal(t, len(expected), i)
 
+	iter = iavlStore.Iterator(nil, []byte("golang"))
+	expected = []string{"aloha"}
+	for i = 0; iter.Valid(); iter.Next() {
+		expectedKey := expected[i]
+		key, value := iter.Key(), iter.Value()
+		assert.EqualValues(t, key, expectedKey)
+		assert.EqualValues(t, value, treeData[expectedKey])
+		i += 1
+	}
+	assert.Equal(t, len(expected), i)
+
+	iter = iavlStore.Iterator(nil, []byte("shalom"))
+	expected = []string{"aloha", "hello"}
+	for i = 0; iter.Valid(); iter.Next() {
+		expectedKey := expected[i]
+		key, value := iter.Key(), iter.Value()
+		assert.EqualValues(t, key, expectedKey)
+		assert.EqualValues(t, value, treeData[expectedKey])
+		i += 1
+	}
+	assert.Equal(t, len(expected), i)
+
+	iter = iavlStore.Iterator(nil, nil)
+	expected = []string{"aloha", "hello"}
+	for i = 0; iter.Valid(); iter.Next() {
+		expectedKey := expected[i]
+		key, value := iter.Key(), iter.Value()
+		assert.EqualValues(t, key, expectedKey)
+		assert.EqualValues(t, value, treeData[expectedKey])
+		i += 1
+	}
+	assert.Equal(t, len(expected), i)
+
 	iter = iavlStore.Iterator([]byte("golang"), nil)
 	expected = []string{"hello"}
 	for i = 0; iter.Valid(); iter.Next() {

From d98ea3764f2d654570c9310a68bbb1c39655e1c8 Mon Sep 17 00:00:00 2001
From: Sunny Aggarwal <sunnya97@gmail.com>
Date: Sun, 1 Apr 2018 00:26:00 +0200
Subject: [PATCH 4/9] it works

---
 store/iavlstore.go      | 5 +++--
 store/iavlstore_test.go | 4 ++++
 2 files changed, 7 insertions(+), 2 deletions(-)

diff --git a/store/iavlstore.go b/store/iavlstore.go
index a1a48722c..330358d8d 100644
--- a/store/iavlstore.go
+++ b/store/iavlstore.go
@@ -138,7 +138,6 @@ func (st *iavlStore) Subspace(prefix []byte) Iterator {
 			}
 		}
 	}
-	fmt.Printf("%v \n", end)
 	return st.Iterator(prefix, end)
 }
 
@@ -242,7 +241,6 @@ func newIAVLIterator(tree *iavl.Tree, start, end []byte, ascending bool) *iavlIt
 		quitCh:    make(chan struct{}),
 		initCh:    make(chan struct{}),
 	}
-	fmt.Printf("%v   %v \n", iter.start, iter.end)
 	go iter.iterateRoutine()
 	go iter.initRoutine()
 	return iter
@@ -356,6 +354,9 @@ func (iter *iavlIterator) assertIsValid() {
 //----------------------------------------
 
 func cp(bz []byte) (ret []byte) {
+	if bz == nil {
+		return nil
+	}
 	ret = make([]byte, len(bz))
 	copy(ret, bz)
 	return ret
diff --git a/store/iavlstore_test.go b/store/iavlstore_test.go
index 02b0d58bb..406d26926 100644
--- a/store/iavlstore_test.go
+++ b/store/iavlstore_test.go
@@ -150,6 +150,10 @@ func TestIAVLSubspace(t *testing.T) {
 	iavlStore.Set([]byte{byte(55), byte(255), byte(255), byte(0)}, []byte("test4"))
 	iavlStore.Set([]byte{byte(55), byte(255), byte(255), byte(1)}, []byte("test4"))
 	iavlStore.Set([]byte{byte(55), byte(255), byte(255), byte(255)}, []byte("test4"))
+	iavlStore.Set([]byte{byte(255), byte(255), byte(0)}, []byte("test4"))
+	iavlStore.Set([]byte{byte(255), byte(255), byte(1)}, []byte("test4"))
+	iavlStore.Set([]byte{byte(255), byte(255), byte(255)}, []byte("test4"))
+
 	i := 0
 
 	iter := iavlStore.Subspace([]byte("test"))

From c441ccdf01efdbbb11ea5116b58dc76672558e06 Mon Sep 17 00:00:00 2001
From: Sunny Aggarwal <sunnya97@gmail.com>
Date: Sun, 1 Apr 2018 18:00:28 +0200
Subject: [PATCH 5/9] added more test

---
 store/cachekvstore.go   | 11 ++++++++
 store/dbstoreadapter.go |  8 ++++++
 store/iavlstore.go      | 34 ++++++++----------------
 store/iavlstore_test.go | 59 +++++++++++++++++++++++++++++++++++++++++
 types/store.go          | 33 +++++++++++++++++++++++
 5 files changed, 122 insertions(+), 23 deletions(-)

diff --git a/store/cachekvstore.go b/store/cachekvstore.go
index e075e7847..f6b0e7a5e 100644
--- a/store/cachekvstore.go
+++ b/store/cachekvstore.go
@@ -5,6 +5,7 @@ import (
 	"sort"
 	"sync"
 
+	sdk "github.com/cosmos/cosmos-sdk/types"
 	cmn "github.com/tendermint/tmlibs/common"
 )
 
@@ -134,6 +135,16 @@ func (ci *cacheKVStore) ReverseIterator(start, end []byte) Iterator {
 	return ci.iterator(start, end, false)
 }
 
+// Implements KVStore.
+func (ci *cacheKVStore) Subspace(prefix []byte) Iterator {
+	return ci.iterator(prefix, sdk.PrefixEndBytes(prefix), true)
+}
+
+// Implements KVStore.
+func (ci *cacheKVStore) ReverseSubspace(prefix []byte) Iterator {
+	return ci.iterator(prefix, sdk.PrefixEndBytes(prefix), false)
+}
+
 func (ci *cacheKVStore) iterator(start, end []byte, ascending bool) Iterator {
 	var parent, cache Iterator
 	if ascending {
diff --git a/store/dbstoreadapter.go b/store/dbstoreadapter.go
index a1b580fd4..39309aaf2 100644
--- a/store/dbstoreadapter.go
+++ b/store/dbstoreadapter.go
@@ -19,5 +19,13 @@ func (dsa dbStoreAdapter) CacheWrap() CacheWrap {
 	return NewCacheKVStore(dsa)
 }
 
+func (dsa dbStoreAdapter) Subspace(prefix []byte) Iterator {
+	return dsa.Iterator(prefix, sdk.PrefixEndBytes(prefix))
+}
+
+func (dsa dbStoreAdapter) ReverseSubspace(prefix []byte) Iterator {
+	return dsa.ReverseIterator(prefix, sdk.PrefixEndBytes(prefix))
+}
+
 // dbm.DB implements KVStore so we can CacheKVStore it.
 var _ KVStore = dbStoreAdapter{dbm.DB(nil)}
diff --git a/store/iavlstore.go b/store/iavlstore.go
index 330358d8d..b27aacb2b 100644
--- a/store/iavlstore.go
+++ b/store/iavlstore.go
@@ -119,33 +119,21 @@ func (st *iavlStore) Iterator(start, end []byte) Iterator {
 	return newIAVLIterator(st.tree.Tree(), start, end, true)
 }
 
-func (st *iavlStore) Subspace(prefix []byte) Iterator {
-	end := make([]byte, len(prefix))
-	copy(end, prefix)
-	finished := false
-	i := 1
-
-	for !finished {
-		if end[len(end)-i] != byte(255) {
-			end[len(end)-i]++
-			finished = true
-		} else {
-			end[len(end)-i]++
-			i++
-			if i > len(end) {
-				end = nil
-				finished = true
-			}
-		}
-	}
-	return st.Iterator(prefix, end)
-}
-
-// Implements IterKVStore.
+// Implements KVStore.
 func (st *iavlStore) ReverseIterator(start, end []byte) Iterator {
 	return newIAVLIterator(st.tree.Tree(), start, end, false)
 }
 
+// Implements KVStore.
+func (st *iavlStore) Subspace(prefix []byte) Iterator {
+	return st.Iterator(prefix, sdk.PrefixEndBytes(prefix))
+}
+
+// Implements KVStore.
+func (st *iavlStore) ReverseSubspace(prefix []byte) Iterator {
+	return st.ReverseIterator(prefix, sdk.PrefixEndBytes(prefix))
+}
+
 // Query implements ABCI interface, allows queries
 //
 // by default we will return from (latest height -1),
diff --git a/store/iavlstore_test.go b/store/iavlstore_test.go
index 406d26926..2c4c0ea00 100644
--- a/store/iavlstore_test.go
+++ b/store/iavlstore_test.go
@@ -198,6 +198,65 @@ func TestIAVLSubspace(t *testing.T) {
 	assert.Equal(t, len(expected), i)
 }
 
+func TestIAVLReverseSubspace(t *testing.T) {
+	db := dbm.NewMemDB()
+	tree, _ := newTree(t, db)
+	iavlStore := newIAVLStore(tree, numHistory)
+
+	iavlStore.Set([]byte("test1"), []byte("test1"))
+	iavlStore.Set([]byte("test2"), []byte("test2"))
+	iavlStore.Set([]byte("test3"), []byte("test3"))
+	iavlStore.Set([]byte{byte(55), byte(255), byte(255), byte(0)}, []byte("test4"))
+	iavlStore.Set([]byte{byte(55), byte(255), byte(255), byte(1)}, []byte("test4"))
+	iavlStore.Set([]byte{byte(55), byte(255), byte(255), byte(255)}, []byte("test4"))
+	iavlStore.Set([]byte{byte(255), byte(255), byte(0)}, []byte("test4"))
+	iavlStore.Set([]byte{byte(255), byte(255), byte(1)}, []byte("test4"))
+	iavlStore.Set([]byte{byte(255), byte(255), byte(255)}, []byte("test4"))
+
+	i := 0
+
+	iter := iavlStore.ReverseSubspace([]byte("test"))
+	expected := []string{"test3", "test2", "test1"}
+	for i = 0; iter.Valid(); iter.Next() {
+		expectedKey := expected[i]
+		key, value := iter.Key(), iter.Value()
+		assert.EqualValues(t, key, expectedKey)
+		assert.EqualValues(t, value, expectedKey)
+		i += 1
+	}
+	assert.Equal(t, len(expected), i)
+
+	iter = iavlStore.ReverseSubspace([]byte{byte(55), byte(255), byte(255)})
+	expected2 := [][]byte{
+		[]byte{byte(55), byte(255), byte(255), byte(255)},
+		[]byte{byte(55), byte(255), byte(255), byte(1)},
+		[]byte{byte(55), byte(255), byte(255), byte(0)},
+	}
+	for i = 0; iter.Valid(); iter.Next() {
+		expectedKey := expected2[i]
+		key, value := iter.Key(), iter.Value()
+		assert.EqualValues(t, key, expectedKey)
+		assert.EqualValues(t, value, []byte("test4"))
+		i += 1
+	}
+	assert.Equal(t, len(expected), i)
+
+	iter = iavlStore.ReverseSubspace([]byte{byte(255), byte(255)})
+	expected2 = [][]byte{
+		[]byte{byte(255), byte(255), byte(255)},
+		[]byte{byte(255), byte(255), byte(1)},
+		[]byte{byte(255), byte(255), byte(0)},
+	}
+	for i = 0; iter.Valid(); iter.Next() {
+		expectedKey := expected2[i]
+		key, value := iter.Key(), iter.Value()
+		assert.EqualValues(t, key, expectedKey)
+		assert.EqualValues(t, value, []byte("test4"))
+		i += 1
+	}
+	assert.Equal(t, len(expected), i)
+}
+
 func TestIAVLStoreQuery(t *testing.T) {
 	db := dbm.NewMemDB()
 	tree := iavl.NewVersionedTree(db, cacheSize)
diff --git a/types/store.go b/types/store.go
index ef2e9154b..9034ea6f3 100644
--- a/types/store.go
+++ b/types/store.go
@@ -111,6 +111,14 @@ type KVStore interface {
 	// CONTRACT: No writes may happen within a domain while an iterator exists over it.
 	ReverseIterator(start, end []byte) Iterator
 
+	// Iterator over all the keys with a certain prefix in ascending order.
+	// CONTRACT: No writes may happen within a domain while an iterator exists over it.
+	Subspace(prefix []byte) Iterator
+
+	// Iterator over all the keys with a certain prefix in descending order.
+	// CONTRACT: No writes may happen within a domain while an iterator exists over it.
+	ReverseSubspace(prefix []byte) Iterator
+
 	// TODO Not yet implemented.
 	// CreateSubKVStore(key *storeKey) (KVStore, error)
 
@@ -222,3 +230,28 @@ func (key *KVStoreKey) Name() string {
 func (key *KVStoreKey) String() string {
 	return fmt.Sprintf("KVStoreKey{%p, %s}", key, key.name)
 }
+
+// TODO: Move to TmLibs
+func PrefixEndBytes(prefix []byte) []byte {
+	if prefix == nil {
+		return nil
+	}
+
+	end := make([]byte, len(prefix))
+	copy(end, prefix)
+	finished := false
+
+	for !finished {
+		if end[len(end)-1] != byte(255) {
+			end[len(end)-1]++
+			finished = true
+		} else {
+			end = end[:len(end)-1]
+			if len(end) == 0 {
+				end = nil
+				finished = true
+			}
+		}
+	}
+	return end
+}

From f10983ba06e0ed5aded8d473b6c42100c91b1371 Mon Sep 17 00:00:00 2001
From: Sunny Aggarwal <sunnya97@gmail.com>
Date: Thu, 5 Apr 2018 21:54:30 +0200
Subject: [PATCH 6/9] address review

---
 store/cachekvstore.go   |  4 ++--
 store/dbstoreadapter.go |  4 ++--
 store/iavlstore.go      |  4 ++--
 store/iavlstore_test.go | 19 ++++++++++---------
 types/store.go          |  4 ++--
 5 files changed, 18 insertions(+), 17 deletions(-)

diff --git a/store/cachekvstore.go b/store/cachekvstore.go
index f6b0e7a5e..6c5cc9542 100644
--- a/store/cachekvstore.go
+++ b/store/cachekvstore.go
@@ -136,12 +136,12 @@ func (ci *cacheKVStore) ReverseIterator(start, end []byte) Iterator {
 }
 
 // Implements KVStore.
-func (ci *cacheKVStore) Subspace(prefix []byte) Iterator {
+func (ci *cacheKVStore) SubspaceIterator(prefix []byte) Iterator {
 	return ci.iterator(prefix, sdk.PrefixEndBytes(prefix), true)
 }
 
 // Implements KVStore.
-func (ci *cacheKVStore) ReverseSubspace(prefix []byte) Iterator {
+func (ci *cacheKVStore) ReverseSubspaceIterator(prefix []byte) Iterator {
 	return ci.iterator(prefix, sdk.PrefixEndBytes(prefix), false)
 }
 
diff --git a/store/dbstoreadapter.go b/store/dbstoreadapter.go
index 39309aaf2..10c175a99 100644
--- a/store/dbstoreadapter.go
+++ b/store/dbstoreadapter.go
@@ -19,11 +19,11 @@ func (dsa dbStoreAdapter) CacheWrap() CacheWrap {
 	return NewCacheKVStore(dsa)
 }
 
-func (dsa dbStoreAdapter) Subspace(prefix []byte) Iterator {
+func (dsa dbStoreAdapter) SubspaceIterator(prefix []byte) Iterator {
 	return dsa.Iterator(prefix, sdk.PrefixEndBytes(prefix))
 }
 
-func (dsa dbStoreAdapter) ReverseSubspace(prefix []byte) Iterator {
+func (dsa dbStoreAdapter) ReverseSubspaceIterator(prefix []byte) Iterator {
 	return dsa.ReverseIterator(prefix, sdk.PrefixEndBytes(prefix))
 }
 
diff --git a/store/iavlstore.go b/store/iavlstore.go
index b27aacb2b..e0b93a1ab 100644
--- a/store/iavlstore.go
+++ b/store/iavlstore.go
@@ -125,12 +125,12 @@ func (st *iavlStore) ReverseIterator(start, end []byte) Iterator {
 }
 
 // Implements KVStore.
-func (st *iavlStore) Subspace(prefix []byte) Iterator {
+func (st *iavlStore) SubspaceIterator(prefix []byte) Iterator {
 	return st.Iterator(prefix, sdk.PrefixEndBytes(prefix))
 }
 
 // Implements KVStore.
-func (st *iavlStore) ReverseSubspace(prefix []byte) Iterator {
+func (st *iavlStore) ReverseSubspaceIterator(prefix []byte) Iterator {
 	return st.ReverseIterator(prefix, sdk.PrefixEndBytes(prefix))
 }
 
diff --git a/store/iavlstore_test.go b/store/iavlstore_test.go
index 2c4c0ea00..824617c26 100644
--- a/store/iavlstore_test.go
+++ b/store/iavlstore_test.go
@@ -73,7 +73,8 @@ func TestIAVLIterator(t *testing.T) {
 	iavlStore := newIAVLStore(tree, numHistory)
 	iter := iavlStore.Iterator([]byte("aloha"), []byte("hellz"))
 	expected := []string{"aloha", "hello"}
-	i := 0
+	var i int
+
 	for i = 0; iter.Valid(); iter.Next() {
 		expectedKey := expected[i]
 		key, value := iter.Key(), iter.Value()
@@ -139,7 +140,7 @@ func TestIAVLIterator(t *testing.T) {
 	assert.Equal(t, len(expected), i)
 }
 
-func TestIAVLSubspace(t *testing.T) {
+func TestIAVLSubspaceIterator(t *testing.T) {
 	db := dbm.NewMemDB()
 	tree, _ := newTree(t, db)
 	iavlStore := newIAVLStore(tree, numHistory)
@@ -156,7 +157,7 @@ func TestIAVLSubspace(t *testing.T) {
 
 	i := 0
 
-	iter := iavlStore.Subspace([]byte("test"))
+	iter := iavlStore.SubspaceIterator([]byte("test"))
 	expected := []string{"test1", "test2", "test3"}
 	for i = 0; iter.Valid(); iter.Next() {
 		expectedKey := expected[i]
@@ -167,7 +168,7 @@ func TestIAVLSubspace(t *testing.T) {
 	}
 	assert.Equal(t, len(expected), i)
 
-	iter = iavlStore.Subspace([]byte{byte(55), byte(255), byte(255)})
+	iter = iavlStore.SubspaceIterator([]byte{byte(55), byte(255), byte(255)})
 	expected2 := [][]byte{
 		[]byte{byte(55), byte(255), byte(255), byte(0)},
 		[]byte{byte(55), byte(255), byte(255), byte(1)},
@@ -182,7 +183,7 @@ func TestIAVLSubspace(t *testing.T) {
 	}
 	assert.Equal(t, len(expected), i)
 
-	iter = iavlStore.Subspace([]byte{byte(255), byte(255)})
+	iter = iavlStore.SubspaceIterator([]byte{byte(255), byte(255)})
 	expected2 = [][]byte{
 		[]byte{byte(255), byte(255), byte(0)},
 		[]byte{byte(255), byte(255), byte(1)},
@@ -198,7 +199,7 @@ func TestIAVLSubspace(t *testing.T) {
 	assert.Equal(t, len(expected), i)
 }
 
-func TestIAVLReverseSubspace(t *testing.T) {
+func TestIAVLReverseSubspaceIterator(t *testing.T) {
 	db := dbm.NewMemDB()
 	tree, _ := newTree(t, db)
 	iavlStore := newIAVLStore(tree, numHistory)
@@ -215,7 +216,7 @@ func TestIAVLReverseSubspace(t *testing.T) {
 
 	i := 0
 
-	iter := iavlStore.ReverseSubspace([]byte("test"))
+	iter := iavlStore.ReverseSubspaceIterator([]byte("test"))
 	expected := []string{"test3", "test2", "test1"}
 	for i = 0; iter.Valid(); iter.Next() {
 		expectedKey := expected[i]
@@ -226,7 +227,7 @@ func TestIAVLReverseSubspace(t *testing.T) {
 	}
 	assert.Equal(t, len(expected), i)
 
-	iter = iavlStore.ReverseSubspace([]byte{byte(55), byte(255), byte(255)})
+	iter = iavlStore.ReverseSubspaceIterator([]byte{byte(55), byte(255), byte(255)})
 	expected2 := [][]byte{
 		[]byte{byte(55), byte(255), byte(255), byte(255)},
 		[]byte{byte(55), byte(255), byte(255), byte(1)},
@@ -241,7 +242,7 @@ func TestIAVLReverseSubspace(t *testing.T) {
 	}
 	assert.Equal(t, len(expected), i)
 
-	iter = iavlStore.ReverseSubspace([]byte{byte(255), byte(255)})
+	iter = iavlStore.ReverseSubspaceIterator([]byte{byte(255), byte(255)})
 	expected2 = [][]byte{
 		[]byte{byte(255), byte(255), byte(255)},
 		[]byte{byte(255), byte(255), byte(1)},
diff --git a/types/store.go b/types/store.go
index 9034ea6f3..9034e7930 100644
--- a/types/store.go
+++ b/types/store.go
@@ -113,11 +113,11 @@ type KVStore interface {
 
 	// Iterator over all the keys with a certain prefix in ascending order.
 	// CONTRACT: No writes may happen within a domain while an iterator exists over it.
-	Subspace(prefix []byte) Iterator
+	SubspaceIterator(prefix []byte) Iterator
 
 	// Iterator over all the keys with a certain prefix in descending order.
 	// CONTRACT: No writes may happen within a domain while an iterator exists over it.
-	ReverseSubspace(prefix []byte) Iterator
+	ReverseSubspaceIterator(prefix []byte) Iterator
 
 	// TODO Not yet implemented.
 	// CreateSubKVStore(key *storeKey) (KVStore, error)

From 4bcfcd5cc8972b723e006e7ebc8c13cb6f4373fe Mon Sep 17 00:00:00 2001
From: Sunny Aggarwal <sunnya97@gmail.com>
Date: Fri, 6 Apr 2018 11:29:25 +0200
Subject: [PATCH 7/9] added comments and got rid of fixed variable

---
 Gopkg.lock     |  2 +-
 types/store.go | 11 ++++++-----
 2 files changed, 7 insertions(+), 6 deletions(-)

diff --git a/Gopkg.lock b/Gopkg.lock
index 50a17e1fb..2de9e117e 100644
--- a/Gopkg.lock
+++ b/Gopkg.lock
@@ -458,6 +458,6 @@
 [solve-meta]
   analyzer-name = "dep"
   analyzer-version = 1
-  inputs-digest = "ed1f3f7f1728cd02945f90ca780e9bdc982573a36a5cc8d7e9f19fb40ba2ca19"
+  inputs-digest = "67298e1f8058b85f082dbd32123f2779b11bda282616e595141dba41a8675c39"
   solver-name = "gps-cdcl"
   solver-version = 1
diff --git a/types/store.go b/types/store.go
index 9034e7930..7b73570ca 100644
--- a/types/store.go
+++ b/types/store.go
@@ -231,7 +231,9 @@ func (key *KVStoreKey) String() string {
 	return fmt.Sprintf("KVStoreKey{%p, %s}", key, key.name)
 }
 
-// TODO: Move to TmLibs
+// PrefixEndBytes returns the []byte that would end a
+// range query for all []byte with a certain prefix
+// Deals with last byte of prefix being FF without overflowing
 func PrefixEndBytes(prefix []byte) []byte {
 	if prefix == nil {
 		return nil
@@ -239,17 +241,16 @@ func PrefixEndBytes(prefix []byte) []byte {
 
 	end := make([]byte, len(prefix))
 	copy(end, prefix)
-	finished := false
 
-	for !finished {
+	for {
 		if end[len(end)-1] != byte(255) {
 			end[len(end)-1]++
-			finished = true
+			break
 		} else {
 			end = end[:len(end)-1]
 			if len(end) == 0 {
 				end = nil
-				finished = true
+				break
 			}
 		}
 	}

From 9b40cf184f6b05594e7e5064d88afc18a7d3e525 Mon Sep 17 00:00:00 2001
From: Sunny Aggarwal <sunnya97@gmail.com>
Date: Sun, 8 Apr 2018 00:58:03 +0200
Subject: [PATCH 8/9] added PrefixBytesTest

---
 types/store_test.go | 28 ++++++++++++++++++++++++++++
 1 file changed, 28 insertions(+)
 create mode 100644 types/store_test.go

diff --git a/types/store_test.go b/types/store_test.go
new file mode 100644
index 000000000..2fd944185
--- /dev/null
+++ b/types/store_test.go
@@ -0,0 +1,28 @@
+package types
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestPrefixEndBytes(t *testing.T) {
+	assert := assert.New(t)
+
+	var testCases = []struct {
+		prefix   []byte
+		expected []byte
+	}{
+		{[]byte{byte(55), byte(255), byte(255), byte(0)}, []byte{byte(55), byte(255), byte(255), byte(1)}},
+		{[]byte{byte(55), byte(255), byte(255), byte(15)}, []byte{byte(55), byte(255), byte(255), byte(16)}},
+		{[]byte{byte(55), byte(200), byte(255)}, []byte{byte(55), byte(201)}},
+		{[]byte{byte(55), byte(255), byte(255)}, []byte{byte(56)}},
+		{[]byte{byte(255), byte(255), byte(255)}, nil},
+		{nil, nil},
+	}
+
+	for _, test := range testCases {
+		end := PrefixEndBytes(test.prefix)
+		assert.Equal(test.expected, end)
+	}
+}

From 69448f90e5f796146ce343241431bc5b96015e17 Mon Sep 17 00:00:00 2001
From: Sunny Aggarwal <sunnya97@gmail.com>
Date: Tue, 10 Apr 2018 01:32:04 +0200
Subject: [PATCH 9/9] added just FF byte

---
 types/store_test.go | 1 +
 1 file changed, 1 insertion(+)

diff --git a/types/store_test.go b/types/store_test.go
index 2fd944185..43dd1f5d3 100644
--- a/types/store_test.go
+++ b/types/store_test.go
@@ -18,6 +18,7 @@ func TestPrefixEndBytes(t *testing.T) {
 		{[]byte{byte(55), byte(200), byte(255)}, []byte{byte(55), byte(201)}},
 		{[]byte{byte(55), byte(255), byte(255)}, []byte{byte(56)}},
 		{[]byte{byte(255), byte(255), byte(255)}, nil},
+		{[]byte{byte(255)}, nil},
 		{nil, nil},
 	}