Merge pull request #837 from cosmos/joon/824-cachecontext

Add CacheContext

CHANGELOG.md

@@ -7,6 +7,10 @@ BREAKING CHANGES
 * Remove go-wire, use go-amino
 * [store] Add `SubspaceIterator` and `ReverseSubspaceIterator` to `KVStore` interface
 
+FEATURES:
+
+* Add CacheContext
+
 ## 0.14.1 (April 9, 2018)
 
 BUG FIXES

types/context.go

@@ -171,6 +171,14 @@ func (c Context) WithTxBytes(txBytes []byte) Context {
 	return c.withValue(contextKeyTxBytes, txBytes)
 }
 
+// Cache the multistore and return a new cached context. The cached context is
+// written to the context when writeCache is called.
+func (c Context) CacheContext() (cc Context, writeCache func()) {
+	cms := c.multiStore().CacheMultiStore()
+	cc = c.WithMultiStore(cms)
+	return cc, cms.Write
+}
+
 //----------------------------------------
 // thePast
 

types/context_test.go

@@ -3,6 +3,11 @@ package types_test
 import (
 	"testing"
 
+	"github.com/stretchr/testify/assert"
+
+	dbm "github.com/tendermint/tmlibs/db"
+
+	"github.com/cosmos/cosmos-sdk/store"
 	"github.com/cosmos/cosmos-sdk/types"
 	abci "github.com/tendermint/abci/types"
 )
@@ -18,3 +23,39 @@ func TestContextGetOpShouldNeverPanic(t *testing.T) {
 		_, _ = ctx.GetOp(index)
 	}
 }
+
+func defaultContext(key types.StoreKey) types.Context {
+	db := dbm.NewMemDB()
+	cms := store.NewCommitMultiStore(db)
+	cms.MountStoreWithDB(key, types.StoreTypeIAVL, db)
+	cms.LoadLatestVersion()
+	ctx := types.NewContext(cms, abci.Header{}, false, nil)
+	return ctx
+}
+
+func TestCacheContext(t *testing.T) {
+	key := types.NewKVStoreKey(t.Name())
+	k1 := []byte("hello")
+	v1 := []byte("world")
+	k2 := []byte("key")
+	v2 := []byte("value")
+
+	ctx := defaultContext(key)
+	store := ctx.KVStore(key)
+	store.Set(k1, v1)
+	assert.Equal(t, v1, store.Get(k1))
+	assert.Nil(t, store.Get(k2))
+
+	cctx, write := ctx.CacheContext()
+	cstore := cctx.KVStore(key)
+	assert.Equal(t, v1, cstore.Get(k1))
+	assert.Nil(t, cstore.Get(k2))
+
+	cstore.Set(k2, v2)
+	assert.Equal(t, v2, cstore.Get(k2))
+	assert.Nil(t, store.Get(k2))
+
+	write()
+
+	assert.Equal(t, v2, store.Get(k2))
+}