feat: state migration from IAVL to SMT (ADR-040) (#10962)

State migration from iavl to smt

This migration works on upgrade handler 
```go

app.registerUpgradeHandlers()


func (app *SimApp) registerUpgradeHandlers() {
	// This is the upgrade plan name we used in the gov proposal.
	upgradeName := "iavl-to-smt-upgrade"
	app.UpgradeKeeper.SetUpgradeHandler(upgradeName, func(ctx sdk.Context, plan upgradetypes.Plan, _ module.VersionMap) (module.VersionMap, error) {
	
	        fromVM := map[string]uint64{
			...
		}
		
	        err := store2.MigrateV2(iavlStore, v2Store)
                if err != nil {
                    return fromVM, err 
                }
		
		return app.mm.RunMigrations(ctx, app.configurator, fromVM)
	})
}
```



## Description

Closes: #XXXX



---

### Author Checklist

*All items are required. Please add a note to the item if the item is not applicable and
please add links to any relevant follow up issues.*

I have...

- [ ] included the correct [type prefix](https://github.com/commitizen/conventional-commit-types/blob/v3.0.0/index.json) in the PR title
- [ ] added `!` to the type prefix if API or client breaking change
- [ ] targeted the correct branch (see [PR Targeting](https://github.com/cosmos/cosmos-sdk/blob/master/CONTRIBUTING.md#pr-targeting))
- [ ] provided a link to the relevant issue or specification
- [ ] followed the guidelines for [building modules](https://github.com/cosmos/cosmos-sdk/blob/master/docs/building-modules)
- [ ] included the necessary unit and integration [tests](https://github.com/cosmos/cosmos-sdk/blob/master/CONTRIBUTING.md#testing)
- [ ] added a changelog entry to `CHANGELOG.md`
- [ ] included comments for [documenting Go code](https://blog.golang.org/godoc)
- [ ] updated the relevant documentation or specification
- [ ] reviewed "Files changed" and left comments if necessary
- [ ] confirmed all CI checks have passed

### Reviewers Checklist

*All items are required. Please add a note if the item is not applicable and please add
your handle next to the items reviewed if you only reviewed selected items.*

I have...

- [ ] confirmed the correct [type prefix](https://github.com/commitizen/conventional-commit-types/blob/v3.0.0/index.json) in the PR title
- [ ] confirmed `!` in the type prefix if API or client breaking change
- [ ] confirmed all author checklist items have been addressed 
- [ ] reviewed state machine logic
- [ ] reviewed API design and naming
- [ ] reviewed documentation is accurate
- [ ] reviewed tests and test coverage
- [ ] manually tested (if applicable)

CHANGELOG.md

@@ -71,6 +71,7 @@ Ref: https://keepachangelog.com/en/1.0.0/
 * [#11179](https://github.com/cosmos/cosmos-sdk/pull/11179) Add state rollback command.
 * [\#10794](https://github.com/cosmos/cosmos-sdk/pull/10794) ADR-040: Add State Sync to V2 Store
 * [\#11234](https://github.com/cosmos/cosmos-sdk/pull/11234) Add `GRPCClient` field to Client Context. If `GRPCClient` field is set to nil, the `Invoke` method would use ABCI query, otherwise use gprc.
+* [\#10962](https://github.com/cosmos/cosmos-sdk/pull/10962) ADR-040: Add state migration from iavl (v1Store) to smt (v2Store) 
 * (types) [\#10948](https://github.com/cosmos/cosmos-sdk/issues/10948) Add `app-db-backend` to the `app.toml` config to replace the compile-time `types.DBbackend` variable.
 
 ### API Breaking Changes

store/rootmulti/snapshot_test.go

@@ -210,7 +210,8 @@ func TestMultistoreSnapshotRestore(t *testing.T) {
 	require.Equal(t, *dummyExtensionItem.GetExtension(), *nextItem.GetExtension())
 
 	assert.Equal(t, source.LastCommitID(), target.LastCommitID())
-	for key, sourceStore := range source.GetStores() {
+	for _, key := range source.StoreKeysByName() {
+		sourceStore := source.GetStoreByName(key.Name()).(types.CommitKVStore)
 		targetStore := target.GetStoreByName(key.Name()).(types.CommitKVStore)
 		switch sourceStore.GetStoreType() {
 		case types.StoreTypeTransient:
@@ -234,7 +235,7 @@ func benchmarkMultistoreSnapshot(b *testing.B, stores uint8, storeKeys uint64) {
 
 	for i := 0; i < b.N; i++ {
 		target := rootmulti.NewStore(dbm.NewMemDB())
-		for key := range source.GetStores() {
+		for _, key := range source.StoreKeysByName() {
 			target.MountStoreWithDB(key, types.StoreTypeIAVL, nil)
 		}
 		err := target.LoadLatestVersion()
@@ -269,7 +270,7 @@ func benchmarkMultistoreSnapshotRestore(b *testing.B, stores uint8, storeKeys ui
 
 	for i := 0; i < b.N; i++ {
 		target := rootmulti.NewStore(dbm.NewMemDB())
-		for key := range source.GetStores() {
+		for _, key := range source.StoreKeysByName() {
 			target.MountStoreWithDB(key, types.StoreTypeIAVL, nil)
 		}
 		err := target.LoadLatestVersion()

store/rootmulti/store.go

@@ -148,9 +148,9 @@ func (rs *Store) GetCommitKVStore(key types.StoreKey) types.CommitKVStore {
 	return rs.stores[key]
 }
 
-// GetStores returns mounted stores
-func (rs *Store) GetStores() map[types.StoreKey]types.CommitKVStore {
-	return rs.stores
+// StoreKeysByName returns mapping storeNames -> StoreKeys
+func (rs *Store) StoreKeysByName() map[string]types.StoreKey {
+	return rs.keysByName
 }
 
 // LoadLatestVersionAndUpgrade implements CommitMultiStore

store/v2alpha1/multi/migration.go

@@ -0,0 +1,68 @@
+package multi
+
+import (
+	dbm "github.com/cosmos/cosmos-sdk/db"
+	"github.com/cosmos/cosmos-sdk/store/iavl"
+	"github.com/cosmos/cosmos-sdk/store/mem"
+	v1Store "github.com/cosmos/cosmos-sdk/store/rootmulti"
+	"github.com/cosmos/cosmos-sdk/store/transient"
+	"github.com/cosmos/cosmos-sdk/store/types"
+	sdkerrors "github.com/cosmos/cosmos-sdk/types/errors"
+)
+
+// MigrateFromV1 will migrate the state from iavl to smt
+func MigrateFromV1(rootMultiStore *v1Store.Store, store2db dbm.DBConnection, storeConfig StoreConfig) (*Store, error) {
+	type namedStore struct {
+		*iavl.Store
+		name string
+	}
+	var stores []namedStore
+	for _, storeKey := range rootMultiStore.StoreKeysByName() {
+		keyName := storeKey.Name()
+		switch store := rootMultiStore.GetStoreByName(keyName).(type) {
+		case *iavl.Store:
+			err := storeConfig.RegisterSubstore(keyName, types.StoreTypePersistent)
+			if err != nil {
+				return nil, err
+			}
+			stores = append(stores, namedStore{name: keyName, Store: store})
+		case *transient.Store, *mem.Store:
+			continue
+		default:
+			return nil, sdkerrors.Wrapf(sdkerrors.ErrLogic, "don't know how to migrate store %q of type %T", keyName, store)
+		}
+	}
+
+	// creating the new store of smt tree
+	rootStore, err := NewStore(store2db, storeConfig)
+	if err != nil {
+		return nil, err
+	}
+
+	// if version is 0 there is no state data to commit
+	if rootMultiStore.LastCommitID().Version == 0 {
+		return rootStore, nil
+	}
+
+	// iterate through the rootmulti stores and save the key/values into smt tree
+	for _, store := range stores {
+		subStore, err := rootStore.getSubstore(store.name)
+		if err != nil {
+			return nil, err
+		}
+		// iterate all iavl tree node key/values
+		iterator := store.Iterator(nil, nil)
+		for ; iterator.Valid(); iterator.Next() {
+			// set the iavl key,values into smt node
+			subStore.Set(iterator.Key(), iterator.Value())
+		}
+	}
+
+	// commit the all key/values from iavl to smt tree (SMT Store)
+	_, err = rootStore.commit(uint64(rootMultiStore.LastCommitID().Version))
+	if err != nil {
+		return nil, err
+	}
+
+	return rootStore, nil
+}

store/v2alpha1/multi/migration_test.go

@@ -0,0 +1,106 @@
+package multi
+
+import (
+	"encoding/binary"
+	"fmt"
+	"math/rand"
+	"testing"
+
+	"github.com/cosmos/cosmos-sdk/db/memdb"
+	"github.com/cosmos/cosmos-sdk/store/iavl"
+	"github.com/cosmos/cosmos-sdk/store/rootmulti"
+	"github.com/cosmos/cosmos-sdk/store/types"
+	"github.com/stretchr/testify/require"
+	dbm "github.com/tendermint/tm-db"
+)
+
+func TestMigrationV2(t *testing.T) {
+	r := rand.New(rand.NewSource(49872768940))
+
+	// setup a rootmulti store
+	db := dbm.NewMemDB()
+	v1Store := rootmulti.NewStore(db)
+
+	// mount the kvStores
+	var keys []*types.KVStoreKey
+	for i := uint8(0); i < 10; i++ {
+		key := types.NewKVStoreKey(fmt.Sprintf("store%v", i))
+		v1Store.MountStoreWithDB(key, types.StoreTypeIAVL, nil)
+		keys = append(keys, key)
+	}
+
+	err := v1Store.LoadLatestVersion()
+	require.Nil(t, err)
+
+	// setup a random test data
+	for _, key := range keys {
+		store := v1Store.GetStore(key).(*iavl.Store)
+		store.Set([]byte("temp_data"), []byte("one"))
+
+		for i := 0; i < len(keys); i++ {
+			k := make([]byte, 8)
+			v := make([]byte, 1024)
+			binary.BigEndian.PutUint64(k, uint64(i))
+			_, err := r.Read(v)
+			if err != nil {
+				panic(err)
+			}
+			store.Set(k, v)
+		}
+	}
+
+	testCases := []struct {
+		testName   string
+		emptyStore bool
+	}{
+		{
+			"Migration With Empty Store",
+			true,
+		},
+		{
+			"Migration From Root Multi Store (IAVL) to SMT ",
+			false,
+		},
+	}
+
+	for _, testCase := range testCases {
+		if !testCase.emptyStore {
+			v1Store.Commit()
+		}
+
+		// setup a new root store of smt
+		db2 := memdb.NewDB()
+		storeConfig := DefaultStoreConfig()
+		// migrating the iavl store (v1) to smt store (v2)
+		v2Store, err := MigrateFromV1(v1Store, db2, storeConfig)
+		require.NoError(t, err)
+
+		for _, key := range keys {
+			v2StoreKVStore := v2Store.GetKVStore(key)
+			if testCase.emptyStore {
+				// check the empty store
+				require.Nil(t, v2StoreKVStore.Get([]byte("temp_data")))
+			} else {
+				require.Equal(t, v2StoreKVStore.Get([]byte("temp_data")), []byte("one"))
+			}
+			require.Equal(t, v2Store.LastCommitID().Version, v1Store.LastCommitID().Version)
+		}
+		err = v2Store.Close()
+		require.NoError(t, err)
+	}
+}
+
+// TestMigrateV2ForEmptyStore checking empty store migration
+func TestMigrateV2ForEmptyStore(t *testing.T) {
+	// setup a rootmulti store
+	db := dbm.NewMemDB()
+	v1Store := rootmulti.NewStore(db)
+	err := v1Store.LoadLatestVersion()
+	require.Nil(t, err)
+	db2 := memdb.NewDB()
+	storeConfig := DefaultStoreConfig()
+	// migrating the iavl store (v1) to smt store (v2)
+	v2Store, err := MigrateFromV1(v1Store, db2, storeConfig)
+	require.NoError(t, err)
+	require.Equal(t, v2Store.LastCommitID(), v1Store.LastCommitID())
+}