From a3bc74f0c8ed999492e7b73c6634d2b06deb1f32 Mon Sep 17 00:00:00 2001
From: rjl493456442 <garyrong0905@gmail.com>
Date: Wed, 9 May 2018 18:03:45 +0800
Subject: [PATCH 1/3] all: get rid of error when create mdb

---
 accounts/abi/bind/backends/simulated.go |  2 +-
 cmd/evm/runner.go                       |  4 +-
 consensus/clique/snapshot_test.go       |  2 +-
 core/bench_test.go                      |  2 +-
 core/block_validator_test.go            |  6 +--
 core/blockchain_test.go                 | 58 ++++++++++++-------------
 core/chain_indexer_test.go              |  2 +-
 core/chain_makers.go                    |  2 +-
 core/chain_makers_test.go               |  2 +-
 core/dao_test.go                        | 14 +++---
 core/genesis.go                         |  2 +-
 core/genesis_test.go                    |  2 +-
 core/helper_test.go                     |  7 +--
 core/rawdb/accessors_chain_test.go      | 16 +++----
 core/rawdb/accessors_indexes_test.go    |  2 +-
 core/state/managed_state_test.go        |  2 +-
 core/state/state_test.go                |  4 +-
 core/state/statedb_test.go              | 12 ++---
 core/state/sync_test.go                 | 14 +++---
 core/tx_pool_test.go                    | 36 +++++++--------
 core/vm/runtime/runtime.go              |  4 +-
 core/vm/runtime/runtime_test.go         |  2 +-
 eth/api_test.go                         |  2 +-
 eth/downloader/downloader_test.go       |  4 +-
 eth/fetcher/fetcher_test.go             |  2 +-
 eth/filters/filter_system_test.go       | 12 ++---
 eth/handler_test.go                     |  4 +-
 eth/helper_test.go                      |  2 +-
 eth/tracers/tracers_test.go             |  2 +-
 ethdb/database_test.go                  |  4 +-
 ethdb/memory_database.go                |  8 ++--
 les/handler_test.go                     | 16 +++----
 les/odr_test.go                         |  4 +-
 les/request_test.go                     |  4 +-
 light/lightchain_test.go                |  4 +-
 light/odr_test.go                       |  4 +-
 light/trie_test.go                      |  8 ++--
 light/txpool_test.go                    |  4 +-
 node/node.go                            |  2 +-
 node/service.go                         |  2 +-
 tests/block_test_util.go                |  2 +-
 tests/state_test_util.go                |  2 +-
 tests/vm_test_util.go                   |  2 +-
 trie/iterator_test.go                   |  4 +-
 trie/proof_test.go                      | 10 ++---
 trie/secure_trie_test.go                |  4 +-
 trie/sync_test.go                       | 20 ++++-----
 trie/trie_test.go                       |  8 ++--
 48 files changed, 166 insertions(+), 171 deletions(-)

diff --git a/accounts/abi/bind/backends/simulated.go b/accounts/abi/bind/backends/simulated.go
index 76c51a40c1a9..7b605e1c1ecf 100644
--- a/accounts/abi/bind/backends/simulated.go
+++ b/accounts/abi/bind/backends/simulated.go
@@ -66,7 +66,7 @@ type SimulatedBackend struct {
 // NewSimulatedBackend creates a new binding backend using a simulated blockchain
 // for testing purposes.
 func NewSimulatedBackend(alloc core.GenesisAlloc) *SimulatedBackend {
-	database, _ := ethdb.NewMemDatabase()
+	database := ethdb.NewMemDatabase()
 	genesis := core.Genesis{Config: params.AllEthashProtocolChanges, Alloc: alloc}
 	genesis.MustCommit(database)
 	blockchain, _ := core.NewBlockChain(database, nil, genesis.Config, ethash.NewFaker(), vm.Config{})
diff --git a/cmd/evm/runner.go b/cmd/evm/runner.go
index 99919304ae14..ef1a96f6dbea 100644
--- a/cmd/evm/runner.go
+++ b/cmd/evm/runner.go
@@ -98,13 +98,13 @@ func runCmd(ctx *cli.Context) error {
 	}
 	if ctx.GlobalString(GenesisFlag.Name) != "" {
 		gen := readGenesis(ctx.GlobalString(GenesisFlag.Name))
-		db, _ := ethdb.NewMemDatabase()
+		db := ethdb.NewMemDatabase()
 		genesis := gen.ToBlock(db)
 		statedb, _ = state.New(genesis.Root(), state.NewDatabase(db))
 		chainConfig = gen.Config
 		blockNumber = gen.Number
 	} else {
-		db, _ := ethdb.NewMemDatabase()
+		db := ethdb.NewMemDatabase()
 		statedb, _ = state.New(common.Hash{}, state.NewDatabase(db))
 	}
 	if ctx.GlobalString(SenderFlag.Name) != "" {
diff --git a/consensus/clique/snapshot_test.go b/consensus/clique/snapshot_test.go
index 91fafcbe07b5..29a837983208 100644
--- a/consensus/clique/snapshot_test.go
+++ b/consensus/clique/snapshot_test.go
@@ -352,7 +352,7 @@ func TestVoting(t *testing.T) {
 			copy(genesis.ExtraData[extraVanity+j*common.AddressLength:], signer[:])
 		}
 		// Create a pristine blockchain with the genesis injected
-		db, _ := ethdb.NewMemDatabase()
+		db := ethdb.NewMemDatabase()
 		genesis.Commit(db)
 
 		// Assemble a chain of headers from the cast votes
diff --git a/core/bench_test.go b/core/bench_test.go
index ee30cfed0e58..748aebe407b2 100644
--- a/core/bench_test.go
+++ b/core/bench_test.go
@@ -149,7 +149,7 @@ func benchInsertChain(b *testing.B, disk bool, gen func(int, *BlockGen)) {
 	// Create the database in memory or in a temporary directory.
 	var db ethdb.Database
 	if !disk {
-		db, _ = ethdb.NewMemDatabase()
+		db = ethdb.NewMemDatabase()
 	} else {
 		dir, err := ioutil.TempDir("", "eth-core-bench")
 		if err != nil {
diff --git a/core/block_validator_test.go b/core/block_validator_test.go
index e334b3c3cdd9..2a171218e32c 100644
--- a/core/block_validator_test.go
+++ b/core/block_validator_test.go
@@ -32,7 +32,7 @@ import (
 func TestHeaderVerification(t *testing.T) {
 	// Create a simple chain to verify
 	var (
-		testdb, _ = ethdb.NewMemDatabase()
+		testdb    = ethdb.NewMemDatabase()
 		gspec     = &Genesis{Config: params.TestChainConfig}
 		genesis   = gspec.MustCommit(testdb)
 		blocks, _ = GenerateChain(params.TestChainConfig, genesis, ethash.NewFaker(), testdb, 8, nil)
@@ -84,7 +84,7 @@ func TestHeaderConcurrentVerification32(t *testing.T) { testHeaderConcurrentVeri
 func testHeaderConcurrentVerification(t *testing.T, threads int) {
 	// Create a simple chain to verify
 	var (
-		testdb, _ = ethdb.NewMemDatabase()
+		testdb    = ethdb.NewMemDatabase()
 		gspec     = &Genesis{Config: params.TestChainConfig}
 		genesis   = gspec.MustCommit(testdb)
 		blocks, _ = GenerateChain(params.TestChainConfig, genesis, ethash.NewFaker(), testdb, 8, nil)
@@ -156,7 +156,7 @@ func TestHeaderConcurrentAbortion32(t *testing.T) { testHeaderConcurrentAbortion
 func testHeaderConcurrentAbortion(t *testing.T, threads int) {
 	// Create a simple chain to verify
 	var (
-		testdb, _ = ethdb.NewMemDatabase()
+		testdb    = ethdb.NewMemDatabase()
 		gspec     = &Genesis{Config: params.TestChainConfig}
 		genesis   = gspec.MustCommit(testdb)
 		blocks, _ = GenerateChain(params.TestChainConfig, genesis, ethash.NewFaker(), testdb, 1024, nil)
diff --git a/core/blockchain_test.go b/core/blockchain_test.go
index c1638c31f838..89c071174f58 100644
--- a/core/blockchain_test.go
+++ b/core/blockchain_test.go
@@ -569,11 +569,11 @@ func testInsertNonceError(t *testing.T, full bool) {
 func TestFastVsFullChains(t *testing.T) {
 	// Configure and generate a sample block chain
 	var (
-		gendb, _ = ethdb.NewMemDatabase()
-		key, _   = crypto.HexToECDSA("b71c71a67e1177ad4e901695e1b4b9ee17ae16c6668d313eac2f96dbcda3f291")
-		address  = crypto.PubkeyToAddress(key.PublicKey)
-		funds    = big.NewInt(1000000000)
-		gspec    = &Genesis{
+		gendb   = ethdb.NewMemDatabase()
+		key, _  = crypto.HexToECDSA("b71c71a67e1177ad4e901695e1b4b9ee17ae16c6668d313eac2f96dbcda3f291")
+		address = crypto.PubkeyToAddress(key.PublicKey)
+		funds   = big.NewInt(1000000000)
+		gspec   = &Genesis{
 			Config: params.TestChainConfig,
 			Alloc:  GenesisAlloc{address: {Balance: funds}},
 		}
@@ -599,7 +599,7 @@ func TestFastVsFullChains(t *testing.T) {
 		}
 	})
 	// Import the chain as an archive node for the comparison baseline
-	archiveDb, _ := ethdb.NewMemDatabase()
+	archiveDb := ethdb.NewMemDatabase()
 	gspec.MustCommit(archiveDb)
 	archive, _ := NewBlockChain(archiveDb, nil, gspec.Config, ethash.NewFaker(), vm.Config{})
 	defer archive.Stop()
@@ -608,7 +608,7 @@ func TestFastVsFullChains(t *testing.T) {
 		t.Fatalf("failed to process block %d: %v", n, err)
 	}
 	// Fast import the chain as a non-archive node to test
-	fastDb, _ := ethdb.NewMemDatabase()
+	fastDb := ethdb.NewMemDatabase()
 	gspec.MustCommit(fastDb)
 	fast, _ := NewBlockChain(fastDb, nil, gspec.Config, ethash.NewFaker(), vm.Config{})
 	defer fast.Stop()
@@ -657,12 +657,12 @@ func TestFastVsFullChains(t *testing.T) {
 func TestLightVsFastVsFullChainHeads(t *testing.T) {
 	// Configure and generate a sample block chain
 	var (
-		gendb, _ = ethdb.NewMemDatabase()
-		key, _   = crypto.HexToECDSA("b71c71a67e1177ad4e901695e1b4b9ee17ae16c6668d313eac2f96dbcda3f291")
-		address  = crypto.PubkeyToAddress(key.PublicKey)
-		funds    = big.NewInt(1000000000)
-		gspec    = &Genesis{Config: params.TestChainConfig, Alloc: GenesisAlloc{address: {Balance: funds}}}
-		genesis  = gspec.MustCommit(gendb)
+		gendb   = ethdb.NewMemDatabase()
+		key, _  = crypto.HexToECDSA("b71c71a67e1177ad4e901695e1b4b9ee17ae16c6668d313eac2f96dbcda3f291")
+		address = crypto.PubkeyToAddress(key.PublicKey)
+		funds   = big.NewInt(1000000000)
+		gspec   = &Genesis{Config: params.TestChainConfig, Alloc: GenesisAlloc{address: {Balance: funds}}}
+		genesis = gspec.MustCommit(gendb)
 	)
 	height := uint64(1024)
 	blocks, receipts := GenerateChain(gspec.Config, genesis, ethash.NewFaker(), gendb, int(height), nil)
@@ -685,7 +685,7 @@ func TestLightVsFastVsFullChainHeads(t *testing.T) {
 		}
 	}
 	// Import the chain as an archive node and ensure all pointers are updated
-	archiveDb, _ := ethdb.NewMemDatabase()
+	archiveDb := ethdb.NewMemDatabase()
 	gspec.MustCommit(archiveDb)
 
 	archive, _ := NewBlockChain(archiveDb, nil, gspec.Config, ethash.NewFaker(), vm.Config{})
@@ -699,7 +699,7 @@ func TestLightVsFastVsFullChainHeads(t *testing.T) {
 	assert(t, "archive", archive, height/2, height/2, height/2)
 
 	// Import the chain as a non-archive node and ensure all pointers are updated
-	fastDb, _ := ethdb.NewMemDatabase()
+	fastDb := ethdb.NewMemDatabase()
 	gspec.MustCommit(fastDb)
 	fast, _ := NewBlockChain(fastDb, nil, gspec.Config, ethash.NewFaker(), vm.Config{})
 	defer fast.Stop()
@@ -719,7 +719,7 @@ func TestLightVsFastVsFullChainHeads(t *testing.T) {
 	assert(t, "fast", fast, height/2, height/2, 0)
 
 	// Import the chain as a light node and ensure all pointers are updated
-	lightDb, _ := ethdb.NewMemDatabase()
+	lightDb := ethdb.NewMemDatabase()
 	gspec.MustCommit(lightDb)
 
 	light, _ := NewBlockChain(lightDb, nil, gspec.Config, ethash.NewFaker(), vm.Config{})
@@ -742,7 +742,7 @@ func TestChainTxReorgs(t *testing.T) {
 		addr1   = crypto.PubkeyToAddress(key1.PublicKey)
 		addr2   = crypto.PubkeyToAddress(key2.PublicKey)
 		addr3   = crypto.PubkeyToAddress(key3.PublicKey)
-		db, _   = ethdb.NewMemDatabase()
+		db      = ethdb.NewMemDatabase()
 		gspec   = &Genesis{
 			Config:   params.TestChainConfig,
 			GasLimit: 3141592,
@@ -854,7 +854,7 @@ func TestLogReorgs(t *testing.T) {
 	var (
 		key1, _ = crypto.HexToECDSA("b71c71a67e1177ad4e901695e1b4b9ee17ae16c6668d313eac2f96dbcda3f291")
 		addr1   = crypto.PubkeyToAddress(key1.PublicKey)
-		db, _   = ethdb.NewMemDatabase()
+		db      = ethdb.NewMemDatabase()
 		// this code generates a log
 		code    = common.Hex2Bytes("60606040525b7f24ec1d3ff24c2f6ff210738839dbc339cd45a5294d85c79361016243157aae7b60405180905060405180910390a15b600a8060416000396000f360606040526008565b00")
 		gspec   = &Genesis{Config: params.TestChainConfig, Alloc: GenesisAlloc{addr1: {Balance: big.NewInt(10000000000000)}}}
@@ -898,7 +898,7 @@ func TestLogReorgs(t *testing.T) {
 
 func TestReorgSideEvent(t *testing.T) {
 	var (
-		db, _   = ethdb.NewMemDatabase()
+		db      = ethdb.NewMemDatabase()
 		key1, _ = crypto.HexToECDSA("b71c71a67e1177ad4e901695e1b4b9ee17ae16c6668d313eac2f96dbcda3f291")
 		addr1   = crypto.PubkeyToAddress(key1.PublicKey)
 		gspec   = &Genesis{
@@ -1026,7 +1026,7 @@ func TestCanonicalBlockRetrieval(t *testing.T) {
 func TestEIP155Transition(t *testing.T) {
 	// Configure and generate a sample block chain
 	var (
-		db, _      = ethdb.NewMemDatabase()
+		db         = ethdb.NewMemDatabase()
 		key, _     = crypto.HexToECDSA("b71c71a67e1177ad4e901695e1b4b9ee17ae16c6668d313eac2f96dbcda3f291")
 		address    = crypto.PubkeyToAddress(key.PublicKey)
 		funds      = big.NewInt(1000000000)
@@ -1130,7 +1130,7 @@ func TestEIP155Transition(t *testing.T) {
 func TestEIP161AccountRemoval(t *testing.T) {
 	// Configure and generate a sample block chain
 	var (
-		db, _   = ethdb.NewMemDatabase()
+		db      = ethdb.NewMemDatabase()
 		key, _  = crypto.HexToECDSA("b71c71a67e1177ad4e901695e1b4b9ee17ae16c6668d313eac2f96dbcda3f291")
 		address = crypto.PubkeyToAddress(key.PublicKey)
 		funds   = big.NewInt(1000000000)
@@ -1202,7 +1202,7 @@ func TestBlockchainHeaderchainReorgConsistency(t *testing.T) {
 	// Generate a canonical chain to act as the main dataset
 	engine := ethash.NewFaker()
 
-	db, _ := ethdb.NewMemDatabase()
+	db := ethdb.NewMemDatabase()
 	genesis := new(Genesis).MustCommit(db)
 	blocks, _ := GenerateChain(params.TestChainConfig, genesis, engine, db, 64, func(i int, b *BlockGen) { b.SetCoinbase(common.Address{1}) })
 
@@ -1218,7 +1218,7 @@ func TestBlockchainHeaderchainReorgConsistency(t *testing.T) {
 	}
 	// Import the canonical and fork chain side by side, verifying the current block
 	// and current header consistency
-	diskdb, _ := ethdb.NewMemDatabase()
+	diskdb := ethdb.NewMemDatabase()
 	new(Genesis).MustCommit(diskdb)
 
 	chain, err := NewBlockChain(diskdb, nil, params.TestChainConfig, engine, vm.Config{})
@@ -1247,7 +1247,7 @@ func TestTrieForkGC(t *testing.T) {
 	// Generate a canonical chain to act as the main dataset
 	engine := ethash.NewFaker()
 
-	db, _ := ethdb.NewMemDatabase()
+	db := ethdb.NewMemDatabase()
 	genesis := new(Genesis).MustCommit(db)
 	blocks, _ := GenerateChain(params.TestChainConfig, genesis, engine, db, 2*triesInMemory, func(i int, b *BlockGen) { b.SetCoinbase(common.Address{1}) })
 
@@ -1262,7 +1262,7 @@ func TestTrieForkGC(t *testing.T) {
 		forks[i] = fork[0]
 	}
 	// Import the canonical and fork chain side by side, forcing the trie cache to cache both
-	diskdb, _ := ethdb.NewMemDatabase()
+	diskdb := ethdb.NewMemDatabase()
 	new(Genesis).MustCommit(diskdb)
 
 	chain, err := NewBlockChain(diskdb, nil, params.TestChainConfig, engine, vm.Config{})
@@ -1293,7 +1293,7 @@ func TestLargeReorgTrieGC(t *testing.T) {
 	// Generate the original common chain segment and the two competing forks
 	engine := ethash.NewFaker()
 
-	db, _ := ethdb.NewMemDatabase()
+	db := ethdb.NewMemDatabase()
 	genesis := new(Genesis).MustCommit(db)
 
 	shared, _ := GenerateChain(params.TestChainConfig, genesis, engine, db, 64, func(i int, b *BlockGen) { b.SetCoinbase(common.Address{1}) })
@@ -1301,7 +1301,7 @@ func TestLargeReorgTrieGC(t *testing.T) {
 	competitor, _ := GenerateChain(params.TestChainConfig, shared[len(shared)-1], engine, db, 2*triesInMemory+1, func(i int, b *BlockGen) { b.SetCoinbase(common.Address{3}) })
 
 	// Import the shared chain and the original canonical one
-	diskdb, _ := ethdb.NewMemDatabase()
+	diskdb := ethdb.NewMemDatabase()
 	new(Genesis).MustCommit(diskdb)
 
 	chain, err := NewBlockChain(diskdb, nil, params.TestChainConfig, engine, vm.Config{})
@@ -1361,7 +1361,7 @@ func benchmarkLargeNumberOfValueToNonexisting(b *testing.B, numTxs, numBlocks in
 	)
 	// Generate the original common chain segment and the two competing forks
 	engine := ethash.NewFaker()
-	db, _ := ethdb.NewMemDatabase()
+	db := ethdb.NewMemDatabase()
 	genesis := gspec.MustCommit(db)
 
 	blockGenerator := func(i int, block *BlockGen) {
@@ -1383,7 +1383,7 @@ func benchmarkLargeNumberOfValueToNonexisting(b *testing.B, numTxs, numBlocks in
 	b.ResetTimer()
 	for i := 0; i < b.N; i++ {
 		// Import the shared chain and the original canonical one
-		diskdb, _ := ethdb.NewMemDatabase()
+		diskdb := ethdb.NewMemDatabase()
 		gspec.MustCommit(diskdb)
 
 		chain, err := NewBlockChain(diskdb, nil, params.TestChainConfig, engine, vm.Config{})
diff --git a/core/chain_indexer_test.go b/core/chain_indexer_test.go
index 3205616e8d95..550caf5567c8 100644
--- a/core/chain_indexer_test.go
+++ b/core/chain_indexer_test.go
@@ -48,7 +48,7 @@ func TestChainIndexerWithChildren(t *testing.T) {
 // multiple backends. The section size and required confirmation count parameters
 // are randomized.
 func testChainIndexer(t *testing.T, count int) {
-	db, _ := ethdb.NewMemDatabase()
+	db := ethdb.NewMemDatabase()
 	defer db.Close()
 
 	// Create a chain of indexers and ensure they all report empty
diff --git a/core/chain_makers.go b/core/chain_makers.go
index 31c9e3fb7740..3fb2ecbd92fd 100644
--- a/core/chain_makers.go
+++ b/core/chain_makers.go
@@ -258,7 +258,7 @@ func makeHeader(chain consensus.ChainReader, parent *types.Block, state *state.S
 func newCanonical(engine consensus.Engine, n int, full bool) (ethdb.Database, *BlockChain, error) {
 	// Initialize a fresh chain with only a genesis block
 	gspec := new(Genesis)
-	db, _ := ethdb.NewMemDatabase()
+	db := ethdb.NewMemDatabase()
 	genesis := gspec.MustCommit(db)
 
 	blockchain, _ := NewBlockChain(db, nil, params.AllEthashProtocolChanges, engine, vm.Config{})
diff --git a/core/chain_makers_test.go b/core/chain_makers_test.go
index 93be43ddce53..5015d1f48e59 100644
--- a/core/chain_makers_test.go
+++ b/core/chain_makers_test.go
@@ -36,7 +36,7 @@ func ExampleGenerateChain() {
 		addr1   = crypto.PubkeyToAddress(key1.PublicKey)
 		addr2   = crypto.PubkeyToAddress(key2.PublicKey)
 		addr3   = crypto.PubkeyToAddress(key3.PublicKey)
-		db, _   = ethdb.NewMemDatabase()
+		db      = ethdb.NewMemDatabase()
 	)
 
 	// Ensure that key1 has some funds in the genesis block.
diff --git a/core/dao_test.go b/core/dao_test.go
index e0a3e3ff3778..284b1d98bde3 100644
--- a/core/dao_test.go
+++ b/core/dao_test.go
@@ -32,13 +32,13 @@ func TestDAOForkRangeExtradata(t *testing.T) {
 	forkBlock := big.NewInt(32)
 
 	// Generate a common prefix for both pro-forkers and non-forkers
-	db, _ := ethdb.NewMemDatabase()
+	db := ethdb.NewMemDatabase()
 	gspec := new(Genesis)
 	genesis := gspec.MustCommit(db)
 	prefix, _ := GenerateChain(params.TestChainConfig, genesis, ethash.NewFaker(), db, int(forkBlock.Int64()-1), func(i int, gen *BlockGen) {})
 
 	// Create the concurrent, conflicting two nodes
-	proDb, _ := ethdb.NewMemDatabase()
+	proDb := ethdb.NewMemDatabase()
 	gspec.MustCommit(proDb)
 
 	proConf := *params.TestChainConfig
@@ -48,7 +48,7 @@ func TestDAOForkRangeExtradata(t *testing.T) {
 	proBc, _ := NewBlockChain(proDb, nil, &proConf, ethash.NewFaker(), vm.Config{})
 	defer proBc.Stop()
 
-	conDb, _ := ethdb.NewMemDatabase()
+	conDb := ethdb.NewMemDatabase()
 	gspec.MustCommit(conDb)
 
 	conConf := *params.TestChainConfig
@@ -67,7 +67,7 @@ func TestDAOForkRangeExtradata(t *testing.T) {
 	// Try to expand both pro-fork and non-fork chains iteratively with other camp's blocks
 	for i := int64(0); i < params.DAOForkExtraRange.Int64(); i++ {
 		// Create a pro-fork block, and try to feed into the no-fork chain
-		db, _ = ethdb.NewMemDatabase()
+		db = ethdb.NewMemDatabase()
 		gspec.MustCommit(db)
 		bc, _ := NewBlockChain(db, nil, &conConf, ethash.NewFaker(), vm.Config{})
 		defer bc.Stop()
@@ -92,7 +92,7 @@ func TestDAOForkRangeExtradata(t *testing.T) {
 			t.Fatalf("contra-fork chain didn't accepted no-fork block: %v", err)
 		}
 		// Create a no-fork block, and try to feed into the pro-fork chain
-		db, _ = ethdb.NewMemDatabase()
+		db = ethdb.NewMemDatabase()
 		gspec.MustCommit(db)
 		bc, _ = NewBlockChain(db, nil, &proConf, ethash.NewFaker(), vm.Config{})
 		defer bc.Stop()
@@ -118,7 +118,7 @@ func TestDAOForkRangeExtradata(t *testing.T) {
 		}
 	}
 	// Verify that contra-forkers accept pro-fork extra-datas after forking finishes
-	db, _ = ethdb.NewMemDatabase()
+	db = ethdb.NewMemDatabase()
 	gspec.MustCommit(db)
 	bc, _ := NewBlockChain(db, nil, &conConf, ethash.NewFaker(), vm.Config{})
 	defer bc.Stop()
@@ -138,7 +138,7 @@ func TestDAOForkRangeExtradata(t *testing.T) {
 		t.Fatalf("contra-fork chain didn't accept pro-fork block post-fork: %v", err)
 	}
 	// Verify that pro-forkers accept contra-fork extra-datas after forking finishes
-	db, _ = ethdb.NewMemDatabase()
+	db = ethdb.NewMemDatabase()
 	gspec.MustCommit(db)
 	bc, _ = NewBlockChain(db, nil, &proConf, ethash.NewFaker(), vm.Config{})
 	defer bc.Stop()
diff --git a/core/genesis.go b/core/genesis.go
index c0a636ab2daf..9190e2ba2241 100644
--- a/core/genesis.go
+++ b/core/genesis.go
@@ -222,7 +222,7 @@ func (g *Genesis) configOrDefault(ghash common.Hash) *params.ChainConfig {
 // to the given database (or discards it if nil).
 func (g *Genesis) ToBlock(db ethdb.Database) *types.Block {
 	if db == nil {
-		db, _ = ethdb.NewMemDatabase()
+		db = ethdb.NewMemDatabase()
 	}
 	statedb, _ := state.New(common.Hash{}, state.NewDatabase(db))
 	for addr, account := range g.Alloc {
diff --git a/core/genesis_test.go b/core/genesis_test.go
index 613434e208a2..2d7f94f8f841 100644
--- a/core/genesis_test.go
+++ b/core/genesis_test.go
@@ -141,7 +141,7 @@ func TestSetupGenesis(t *testing.T) {
 	}
 
 	for _, test := range tests {
-		db, _ := ethdb.NewMemDatabase()
+		db := ethdb.NewMemDatabase()
 		config, hash, err := test.fn(db)
 		// Check the return values.
 		if !reflect.DeepEqual(err, test.wantErr) {
diff --git a/core/helper_test.go b/core/helper_test.go
index 698a2924cb41..00e67de2778e 100644
--- a/core/helper_test.go
+++ b/core/helper_test.go
@@ -18,7 +18,6 @@ package core
 
 import (
 	"container/list"
-	"fmt"
 
 	"github.com/ethereum/go-ethereum/core/types"
 	"github.com/ethereum/go-ethereum/ethdb"
@@ -77,11 +76,7 @@ func (tm *TestManager) Db() ethdb.Database {
 }
 
 func NewTestManager() *TestManager {
-	db, err := ethdb.NewMemDatabase()
-	if err != nil {
-		fmt.Println("Could not create mem-db, failing")
-		return nil
-	}
+	db := ethdb.NewMemDatabase()
 
 	testManager := &TestManager{}
 	testManager.eventMux = new(event.TypeMux)
diff --git a/core/rawdb/accessors_chain_test.go b/core/rawdb/accessors_chain_test.go
index 84c9c9aeb236..9ddae6e2b56b 100644
--- a/core/rawdb/accessors_chain_test.go
+++ b/core/rawdb/accessors_chain_test.go
@@ -30,7 +30,7 @@ import (
 
 // Tests block header storage and retrieval operations.
 func TestHeaderStorage(t *testing.T) {
-	db, _ := ethdb.NewMemDatabase()
+	db := ethdb.NewMemDatabase()
 
 	// Create a test header to move around the database and make sure it's really new
 	header := &types.Header{Number: big.NewInt(42), Extra: []byte("test header")}
@@ -63,7 +63,7 @@ func TestHeaderStorage(t *testing.T) {
 
 // Tests block body storage and retrieval operations.
 func TestBodyStorage(t *testing.T) {
-	db, _ := ethdb.NewMemDatabase()
+	db := ethdb.NewMemDatabase()
 
 	// Create a test body to move around the database and make sure it's really new
 	body := &types.Body{Uncles: []*types.Header{{Extra: []byte("test header")}}}
@@ -101,7 +101,7 @@ func TestBodyStorage(t *testing.T) {
 
 // Tests block storage and retrieval operations.
 func TestBlockStorage(t *testing.T) {
-	db, _ := ethdb.NewMemDatabase()
+	db := ethdb.NewMemDatabase()
 
 	// Create a test block to move around the database and make sure it's really new
 	block := types.NewBlockWithHeader(&types.Header{
@@ -151,7 +151,7 @@ func TestBlockStorage(t *testing.T) {
 
 // Tests that partial block contents don't get reassembled into full blocks.
 func TestPartialBlockStorage(t *testing.T) {
-	db, _ := ethdb.NewMemDatabase()
+	db := ethdb.NewMemDatabase()
 	block := types.NewBlockWithHeader(&types.Header{
 		Extra:       []byte("test block"),
 		UncleHash:   types.EmptyUncleHash,
@@ -185,7 +185,7 @@ func TestPartialBlockStorage(t *testing.T) {
 
 // Tests block total difficulty storage and retrieval operations.
 func TestTdStorage(t *testing.T) {
-	db, _ := ethdb.NewMemDatabase()
+	db := ethdb.NewMemDatabase()
 
 	// Create a test TD to move around the database and make sure it's really new
 	hash, td := common.Hash{}, big.NewInt(314)
@@ -208,7 +208,7 @@ func TestTdStorage(t *testing.T) {
 
 // Tests that canonical numbers can be mapped to hashes and retrieved.
 func TestCanonicalMappingStorage(t *testing.T) {
-	db, _ := ethdb.NewMemDatabase()
+	db := ethdb.NewMemDatabase()
 
 	// Create a test canonical number and assinged hash to move around
 	hash, number := common.Hash{0: 0xff}, uint64(314)
@@ -231,7 +231,7 @@ func TestCanonicalMappingStorage(t *testing.T) {
 
 // Tests that head headers and head blocks can be assigned, individually.
 func TestHeadStorage(t *testing.T) {
-	db, _ := ethdb.NewMemDatabase()
+	db := ethdb.NewMemDatabase()
 
 	blockHead := types.NewBlockWithHeader(&types.Header{Extra: []byte("test block header")})
 	blockFull := types.NewBlockWithHeader(&types.Header{Extra: []byte("test block full")})
@@ -266,7 +266,7 @@ func TestHeadStorage(t *testing.T) {
 
 // Tests that receipts associated with a single block can be stored and retrieved.
 func TestBlockReceiptStorage(t *testing.T) {
-	db, _ := ethdb.NewMemDatabase()
+	db := ethdb.NewMemDatabase()
 
 	receipt1 := &types.Receipt{
 		Status:            types.ReceiptStatusFailed,
diff --git a/core/rawdb/accessors_indexes_test.go b/core/rawdb/accessors_indexes_test.go
index d9c12916341e..d9c10e1490fa 100644
--- a/core/rawdb/accessors_indexes_test.go
+++ b/core/rawdb/accessors_indexes_test.go
@@ -27,7 +27,7 @@ import (
 
 // Tests that positional lookup metadata can be stored and retrieved.
 func TestLookupStorage(t *testing.T) {
-	db, _ := ethdb.NewMemDatabase()
+	db := ethdb.NewMemDatabase()
 
 	tx1 := types.NewTransaction(1, common.BytesToAddress([]byte{0x11}), big.NewInt(111), 1111, big.NewInt(11111), []byte{0x11, 0x11, 0x11})
 	tx2 := types.NewTransaction(2, common.BytesToAddress([]byte{0x22}), big.NewInt(222), 2222, big.NewInt(22222), []byte{0x22, 0x22, 0x22})
diff --git a/core/state/managed_state_test.go b/core/state/managed_state_test.go
index 1cfdd3a890c2..ebe796bc0185 100644
--- a/core/state/managed_state_test.go
+++ b/core/state/managed_state_test.go
@@ -26,7 +26,7 @@ import (
 var addr = common.BytesToAddress([]byte("test"))
 
 func create() (*ManagedState, *account) {
-	db, _ := ethdb.NewMemDatabase()
+	db := ethdb.NewMemDatabase()
 	statedb, _ := New(common.Hash{}, NewDatabase(db))
 	ms := ManageState(statedb)
 	ms.StateDB.SetNonce(addr, 100)
diff --git a/core/state/state_test.go b/core/state/state_test.go
index 6d42d63d8290..8c7412c1ceba 100644
--- a/core/state/state_test.go
+++ b/core/state/state_test.go
@@ -87,7 +87,7 @@ func (s *StateSuite) TestDump(c *checker.C) {
 }
 
 func (s *StateSuite) SetUpTest(c *checker.C) {
-	s.db, _ = ethdb.NewMemDatabase()
+	s.db = ethdb.NewMemDatabase()
 	s.state, _ = New(common.Hash{}, NewDatabase(s.db))
 }
 
@@ -133,7 +133,7 @@ func (s *StateSuite) TestSnapshotEmpty(c *checker.C) {
 // use testing instead of checker because checker does not support
 // printing/logging in tests (-check.vv does not work)
 func TestSnapshot2(t *testing.T) {
-	db, _ := ethdb.NewMemDatabase()
+	db := ethdb.NewMemDatabase()
 	state, _ := New(common.Hash{}, NewDatabase(db))
 
 	stateobjaddr0 := toAddr([]byte("so0"))
diff --git a/core/state/statedb_test.go b/core/state/statedb_test.go
index 420ca745ccc4..9a103aa3c18c 100644
--- a/core/state/statedb_test.go
+++ b/core/state/statedb_test.go
@@ -39,7 +39,7 @@ import (
 // actually committing the state.
 func TestUpdateLeaks(t *testing.T) {
 	// Create an empty state database
-	db, _ := ethdb.NewMemDatabase()
+	db := ethdb.NewMemDatabase()
 	state, _ := New(common.Hash{}, NewDatabase(db))
 
 	// Update it with some accounts
@@ -66,8 +66,8 @@ func TestUpdateLeaks(t *testing.T) {
 // only the one right before the commit.
 func TestIntermediateLeaks(t *testing.T) {
 	// Create two state databases, one transitioning to the final state, the other final from the beginning
-	transDb, _ := ethdb.NewMemDatabase()
-	finalDb, _ := ethdb.NewMemDatabase()
+	transDb := ethdb.NewMemDatabase()
+	finalDb := ethdb.NewMemDatabase()
 	transState, _ := New(common.Hash{}, NewDatabase(transDb))
 	finalState, _ := New(common.Hash{}, NewDatabase(finalDb))
 
@@ -122,7 +122,7 @@ func TestIntermediateLeaks(t *testing.T) {
 // https://github.com/ethereum/go-ethereum/pull/15549.
 func TestCopy(t *testing.T) {
 	// Create a random state test to copy and modify "independently"
-	db, _ := ethdb.NewMemDatabase()
+	db := ethdb.NewMemDatabase()
 	orig, _ := New(common.Hash{}, NewDatabase(db))
 
 	for i := byte(0); i < 255; i++ {
@@ -334,7 +334,7 @@ func (test *snapshotTest) String() string {
 func (test *snapshotTest) run() bool {
 	// Run all actions and create snapshots.
 	var (
-		db, _        = ethdb.NewMemDatabase()
+		db           = ethdb.NewMemDatabase()
 		state, _     = New(common.Hash{}, NewDatabase(db))
 		snapshotRevs = make([]int, len(test.snapshots))
 		sindex       = 0
@@ -426,7 +426,7 @@ func (s *StateSuite) TestTouchDelete(c *check.C) {
 // TestCopyOfCopy tests that modified objects are carried over to the copy, and the copy of the copy.
 // See https://github.com/ethereum/go-ethereum/pull/15225#issuecomment-380191512
 func TestCopyOfCopy(t *testing.T) {
-	db, _ := ethdb.NewMemDatabase()
+	db := ethdb.NewMemDatabase()
 	sdb, _ := New(common.Hash{}, NewDatabase(db))
 	addr := common.HexToAddress("aaaa")
 	sdb.SetBalance(addr, big.NewInt(42))
diff --git a/core/state/sync_test.go b/core/state/sync_test.go
index 8f14a44e7a0e..6ec26d233444 100644
--- a/core/state/sync_test.go
+++ b/core/state/sync_test.go
@@ -38,7 +38,7 @@ type testAccount struct {
 // makeTestState create a sample test state to test node-wise reconstruction.
 func makeTestState() (Database, common.Hash, []*testAccount) {
 	// Create an empty state
-	diskdb, _ := ethdb.NewMemDatabase()
+	diskdb := ethdb.NewMemDatabase()
 	db := NewDatabase(diskdb)
 	state, _ := New(common.Hash{}, db)
 
@@ -125,7 +125,7 @@ func checkStateConsistency(db ethdb.Database, root common.Hash) error {
 // Tests that an empty state is not scheduled for syncing.
 func TestEmptyStateSync(t *testing.T) {
 	empty := common.HexToHash("56e81f171bcc55a6ff8345e692c0f86e5b48e01b996cadc001622fb5e363b421")
-	db, _ := ethdb.NewMemDatabase()
+	db := ethdb.NewMemDatabase()
 	if req := NewStateSync(empty, db).Missing(1); len(req) != 0 {
 		t.Errorf("content requested for empty state: %v", req)
 	}
@@ -141,7 +141,7 @@ func testIterativeStateSync(t *testing.T, batch int) {
 	srcDb, srcRoot, srcAccounts := makeTestState()
 
 	// Create a destination state and sync with the scheduler
-	dstDb, _ := ethdb.NewMemDatabase()
+	dstDb := ethdb.NewMemDatabase()
 	sched := NewStateSync(srcRoot, dstDb)
 
 	queue := append([]common.Hash{}, sched.Missing(batch)...)
@@ -173,7 +173,7 @@ func TestIterativeDelayedStateSync(t *testing.T) {
 	srcDb, srcRoot, srcAccounts := makeTestState()
 
 	// Create a destination state and sync with the scheduler
-	dstDb, _ := ethdb.NewMemDatabase()
+	dstDb := ethdb.NewMemDatabase()
 	sched := NewStateSync(srcRoot, dstDb)
 
 	queue := append([]common.Hash{}, sched.Missing(0)...)
@@ -210,7 +210,7 @@ func testIterativeRandomStateSync(t *testing.T, batch int) {
 	srcDb, srcRoot, srcAccounts := makeTestState()
 
 	// Create a destination state and sync with the scheduler
-	dstDb, _ := ethdb.NewMemDatabase()
+	dstDb := ethdb.NewMemDatabase()
 	sched := NewStateSync(srcRoot, dstDb)
 
 	queue := make(map[common.Hash]struct{})
@@ -250,7 +250,7 @@ func TestIterativeRandomDelayedStateSync(t *testing.T) {
 	srcDb, srcRoot, srcAccounts := makeTestState()
 
 	// Create a destination state and sync with the scheduler
-	dstDb, _ := ethdb.NewMemDatabase()
+	dstDb := ethdb.NewMemDatabase()
 	sched := NewStateSync(srcRoot, dstDb)
 
 	queue := make(map[common.Hash]struct{})
@@ -297,7 +297,7 @@ func TestIncompleteStateSync(t *testing.T) {
 	checkTrieConsistency(srcDb.TrieDB().DiskDB().(ethdb.Database), srcRoot)
 
 	// Create a destination state and sync with the scheduler
-	dstDb, _ := ethdb.NewMemDatabase()
+	dstDb := ethdb.NewMemDatabase()
 	sched := NewStateSync(srcRoot, dstDb)
 
 	added := []common.Hash{}
diff --git a/core/tx_pool_test.go b/core/tx_pool_test.go
index f0f86415d4a4..48104164730a 100644
--- a/core/tx_pool_test.go
+++ b/core/tx_pool_test.go
@@ -78,7 +78,7 @@ func pricedTransaction(nonce uint64, gaslimit uint64, gasprice *big.Int, key *ec
 }
 
 func setupTxPool() (*TxPool, *ecdsa.PrivateKey) {
-	diskdb, _ := ethdb.NewMemDatabase()
+	diskdb := ethdb.NewMemDatabase()
 	statedb, _ := state.New(common.Hash{}, state.NewDatabase(diskdb))
 	blockchain := &testBlockChain{statedb, 1000000, new(event.Feed)}
 
@@ -158,7 +158,7 @@ func (c *testChain) State() (*state.StateDB, error) {
 	// a state change between those fetches.
 	stdb := c.statedb
 	if *c.trigger {
-		db, _ := ethdb.NewMemDatabase()
+		db := ethdb.NewMemDatabase()
 		c.statedb, _ = state.New(common.Hash{}, state.NewDatabase(db))
 		// simulate that the new head block included tx0 and tx1
 		c.statedb.SetNonce(c.address, 2)
@@ -175,7 +175,7 @@ func TestStateChangeDuringTransactionPoolReset(t *testing.T) {
 	t.Parallel()
 
 	var (
-		db, _      = ethdb.NewMemDatabase()
+		db         = ethdb.NewMemDatabase()
 		key, _     = crypto.GenerateKey()
 		address    = crypto.PubkeyToAddress(key.PublicKey)
 		statedb, _ = state.New(common.Hash{}, state.NewDatabase(db))
@@ -332,7 +332,7 @@ func TestTransactionChainFork(t *testing.T) {
 
 	addr := crypto.PubkeyToAddress(key.PublicKey)
 	resetState := func() {
-		db, _ := ethdb.NewMemDatabase()
+		db := ethdb.NewMemDatabase()
 		statedb, _ := state.New(common.Hash{}, state.NewDatabase(db))
 		statedb.AddBalance(addr, big.NewInt(100000000000000))
 
@@ -362,7 +362,7 @@ func TestTransactionDoubleNonce(t *testing.T) {
 
 	addr := crypto.PubkeyToAddress(key.PublicKey)
 	resetState := func() {
-		db, _ := ethdb.NewMemDatabase()
+		db := ethdb.NewMemDatabase()
 		statedb, _ := state.New(common.Hash{}, state.NewDatabase(db))
 		statedb.AddBalance(addr, big.NewInt(100000000000000))
 
@@ -553,7 +553,7 @@ func TestTransactionPostponing(t *testing.T) {
 	t.Parallel()
 
 	// Create the pool to test the postponing with
-	db, _ := ethdb.NewMemDatabase()
+	db := ethdb.NewMemDatabase()
 	statedb, _ := state.New(common.Hash{}, state.NewDatabase(db))
 	blockchain := &testBlockChain{statedb, 1000000, new(event.Feed)}
 
@@ -769,7 +769,7 @@ func testTransactionQueueGlobalLimiting(t *testing.T, nolocals bool) {
 	t.Parallel()
 
 	// Create the pool to test the limit enforcement with
-	db, _ := ethdb.NewMemDatabase()
+	db := ethdb.NewMemDatabase()
 	statedb, _ := state.New(common.Hash{}, state.NewDatabase(db))
 	blockchain := &testBlockChain{statedb, 1000000, new(event.Feed)}
 
@@ -858,7 +858,7 @@ func testTransactionQueueTimeLimiting(t *testing.T, nolocals bool) {
 	evictionInterval = time.Second
 
 	// Create the pool to test the non-expiration enforcement
-	db, _ := ethdb.NewMemDatabase()
+	db := ethdb.NewMemDatabase()
 	statedb, _ := state.New(common.Hash{}, state.NewDatabase(db))
 	blockchain := &testBlockChain{statedb, 1000000, new(event.Feed)}
 
@@ -1013,7 +1013,7 @@ func TestTransactionPendingGlobalLimiting(t *testing.T) {
 	t.Parallel()
 
 	// Create the pool to test the limit enforcement with
-	db, _ := ethdb.NewMemDatabase()
+	db := ethdb.NewMemDatabase()
 	statedb, _ := state.New(common.Hash{}, state.NewDatabase(db))
 	blockchain := &testBlockChain{statedb, 1000000, new(event.Feed)}
 
@@ -1060,7 +1060,7 @@ func TestTransactionCapClearsFromAll(t *testing.T) {
 	t.Parallel()
 
 	// Create the pool to test the limit enforcement with
-	db, _ := ethdb.NewMemDatabase()
+	db := ethdb.NewMemDatabase()
 	statedb, _ := state.New(common.Hash{}, state.NewDatabase(db))
 	blockchain := &testBlockChain{statedb, 1000000, new(event.Feed)}
 
@@ -1095,7 +1095,7 @@ func TestTransactionPendingMinimumAllowance(t *testing.T) {
 	t.Parallel()
 
 	// Create the pool to test the limit enforcement with
-	db, _ := ethdb.NewMemDatabase()
+	db := ethdb.NewMemDatabase()
 	statedb, _ := state.New(common.Hash{}, state.NewDatabase(db))
 	blockchain := &testBlockChain{statedb, 1000000, new(event.Feed)}
 
@@ -1144,7 +1144,7 @@ func TestTransactionPoolRepricing(t *testing.T) {
 	t.Parallel()
 
 	// Create the pool to test the pricing enforcement with
-	db, _ := ethdb.NewMemDatabase()
+	db := ethdb.NewMemDatabase()
 	statedb, _ := state.New(common.Hash{}, state.NewDatabase(db))
 	blockchain := &testBlockChain{statedb, 1000000, new(event.Feed)}
 
@@ -1266,7 +1266,7 @@ func TestTransactionPoolRepricingKeepsLocals(t *testing.T) {
 	t.Parallel()
 
 	// Create the pool to test the pricing enforcement with
-	db, _ := ethdb.NewMemDatabase()
+	db := ethdb.NewMemDatabase()
 	statedb, _ := state.New(common.Hash{}, state.NewDatabase(db))
 	blockchain := &testBlockChain{statedb, 1000000, new(event.Feed)}
 
@@ -1329,7 +1329,7 @@ func TestTransactionPoolUnderpricing(t *testing.T) {
 	t.Parallel()
 
 	// Create the pool to test the pricing enforcement with
-	db, _ := ethdb.NewMemDatabase()
+	db := ethdb.NewMemDatabase()
 	statedb, _ := state.New(common.Hash{}, state.NewDatabase(db))
 	blockchain := &testBlockChain{statedb, 1000000, new(event.Feed)}
 
@@ -1436,7 +1436,7 @@ func TestTransactionPoolStableUnderpricing(t *testing.T) {
 	t.Parallel()
 
 	// Create the pool to test the pricing enforcement with
-	db, _ := ethdb.NewMemDatabase()
+	db := ethdb.NewMemDatabase()
 	statedb, _ := state.New(common.Hash{}, state.NewDatabase(db))
 	blockchain := &testBlockChain{statedb, 1000000, new(event.Feed)}
 
@@ -1503,7 +1503,7 @@ func TestTransactionReplacement(t *testing.T) {
 	t.Parallel()
 
 	// Create the pool to test the pricing enforcement with
-	db, _ := ethdb.NewMemDatabase()
+	db := ethdb.NewMemDatabase()
 	statedb, _ := state.New(common.Hash{}, state.NewDatabase(db))
 	blockchain := &testBlockChain{statedb, 1000000, new(event.Feed)}
 
@@ -1598,7 +1598,7 @@ func testTransactionJournaling(t *testing.T, nolocals bool) {
 	os.Remove(journal)
 
 	// Create the original pool to inject transaction into the journal
-	db, _ := ethdb.NewMemDatabase()
+	db := ethdb.NewMemDatabase()
 	statedb, _ := state.New(common.Hash{}, state.NewDatabase(db))
 	blockchain := &testBlockChain{statedb, 1000000, new(event.Feed)}
 
@@ -1697,7 +1697,7 @@ func TestTransactionStatusCheck(t *testing.T) {
 	t.Parallel()
 
 	// Create the pool to test the status retrievals with
-	db, _ := ethdb.NewMemDatabase()
+	db := ethdb.NewMemDatabase()
 	statedb, _ := state.New(common.Hash{}, state.NewDatabase(db))
 	blockchain := &testBlockChain{statedb, 1000000, new(event.Feed)}
 
diff --git a/core/vm/runtime/runtime.go b/core/vm/runtime/runtime.go
index 5ac5464064ad..8de73e5ab3ef 100644
--- a/core/vm/runtime/runtime.go
+++ b/core/vm/runtime/runtime.go
@@ -99,7 +99,7 @@ func Execute(code, input []byte, cfg *Config) ([]byte, *state.StateDB, error) {
 	setDefaults(cfg)
 
 	if cfg.State == nil {
-		db, _ := ethdb.NewMemDatabase()
+		db := ethdb.NewMemDatabase()
 		cfg.State, _ = state.New(common.Hash{}, state.NewDatabase(db))
 	}
 	var (
@@ -130,7 +130,7 @@ func Create(input []byte, cfg *Config) ([]byte, common.Address, uint64, error) {
 	setDefaults(cfg)
 
 	if cfg.State == nil {
-		db, _ := ethdb.NewMemDatabase()
+		db := ethdb.NewMemDatabase()
 		cfg.State, _ = state.New(common.Hash{}, state.NewDatabase(db))
 	}
 	var (
diff --git a/core/vm/runtime/runtime_test.go b/core/vm/runtime/runtime_test.go
index 2c4dc50265c6..c061dc2ec541 100644
--- a/core/vm/runtime/runtime_test.go
+++ b/core/vm/runtime/runtime_test.go
@@ -94,7 +94,7 @@ func TestExecute(t *testing.T) {
 }
 
 func TestCall(t *testing.T) {
-	db, _ := ethdb.NewMemDatabase()
+	db := ethdb.NewMemDatabase()
 	state, _ := state.New(common.Hash{}, state.NewDatabase(db))
 	address := common.HexToAddress("0x0a")
 	state.SetCode(address, []byte{
diff --git a/eth/api_test.go b/eth/api_test.go
index 900a82bb6a14..ed1889cd26bf 100644
--- a/eth/api_test.go
+++ b/eth/api_test.go
@@ -31,7 +31,7 @@ var dumper = spew.ConfigState{Indent: "    "}
 func TestStorageRangeAt(t *testing.T) {
 	// Create a state where account 0x010000... has a few storage entries.
 	var (
-		db, _    = ethdb.NewMemDatabase()
+		db       = ethdb.NewMemDatabase()
 		state, _ = state.New(common.Hash{}, state.NewDatabase(db))
 		addr     = common.Address{0x01}
 		keys     = []common.Hash{ // hashes of Keys of storage
diff --git a/eth/downloader/downloader_test.go b/eth/downloader/downloader_test.go
index e85e234c0eb1..d1a9a8694b77 100644
--- a/eth/downloader/downloader_test.go
+++ b/eth/downloader/downloader_test.go
@@ -75,7 +75,7 @@ type downloadTester struct {
 
 // newTester creates a new downloader test mocker.
 func newTester() *downloadTester {
-	testdb, _ := ethdb.NewMemDatabase()
+	testdb := ethdb.NewMemDatabase()
 	genesis := core.GenesisBlockForTesting(testdb, testAddress, big.NewInt(1000000000))
 
 	tester := &downloadTester{
@@ -93,7 +93,7 @@ func newTester() *downloadTester {
 		peerChainTds:      make(map[string]map[common.Hash]*big.Int),
 		peerMissingStates: make(map[string]map[common.Hash]bool),
 	}
-	tester.stateDb, _ = ethdb.NewMemDatabase()
+	tester.stateDb = ethdb.NewMemDatabase()
 	tester.stateDb.Put(genesis.Root().Bytes(), []byte{0x00})
 
 	tester.downloader = New(FullSync, tester.stateDb, new(event.TypeMux), tester, nil, tester.dropPeer)
diff --git a/eth/fetcher/fetcher_test.go b/eth/fetcher/fetcher_test.go
index 1e536fcacbeb..3d4f0d1e592b 100644
--- a/eth/fetcher/fetcher_test.go
+++ b/eth/fetcher/fetcher_test.go
@@ -34,7 +34,7 @@ import (
 )
 
 var (
-	testdb, _    = ethdb.NewMemDatabase()
+	testdb       = ethdb.NewMemDatabase()
 	testKey, _   = crypto.HexToECDSA("b71c71a67e1177ad4e901695e1b4b9ee17ae16c6668d313eac2f96dbcda3f291")
 	testAddress  = crypto.PubkeyToAddress(testKey.PublicKey)
 	genesis      = core.GenesisBlockForTesting(testdb, testAddress, big.NewInt(1000000000))
diff --git a/eth/filters/filter_system_test.go b/eth/filters/filter_system_test.go
index 73819eadc09f..b4df24b4718e 100644
--- a/eth/filters/filter_system_test.go
+++ b/eth/filters/filter_system_test.go
@@ -153,7 +153,7 @@ func TestBlockSubscription(t *testing.T) {
 
 	var (
 		mux         = new(event.TypeMux)
-		db, _       = ethdb.NewMemDatabase()
+		db          = ethdb.NewMemDatabase()
 		txFeed      = new(event.Feed)
 		rmLogsFeed  = new(event.Feed)
 		logsFeed    = new(event.Feed)
@@ -210,7 +210,7 @@ func TestPendingTxFilter(t *testing.T) {
 
 	var (
 		mux        = new(event.TypeMux)
-		db, _      = ethdb.NewMemDatabase()
+		db         = ethdb.NewMemDatabase()
 		txFeed     = new(event.Feed)
 		rmLogsFeed = new(event.Feed)
 		logsFeed   = new(event.Feed)
@@ -273,7 +273,7 @@ func TestPendingTxFilter(t *testing.T) {
 func TestLogFilterCreation(t *testing.T) {
 	var (
 		mux        = new(event.TypeMux)
-		db, _      = ethdb.NewMemDatabase()
+		db         = ethdb.NewMemDatabase()
 		txFeed     = new(event.Feed)
 		rmLogsFeed = new(event.Feed)
 		logsFeed   = new(event.Feed)
@@ -322,7 +322,7 @@ func TestInvalidLogFilterCreation(t *testing.T) {
 
 	var (
 		mux        = new(event.TypeMux)
-		db, _      = ethdb.NewMemDatabase()
+		db         = ethdb.NewMemDatabase()
 		txFeed     = new(event.Feed)
 		rmLogsFeed = new(event.Feed)
 		logsFeed   = new(event.Feed)
@@ -352,7 +352,7 @@ func TestLogFilter(t *testing.T) {
 
 	var (
 		mux        = new(event.TypeMux)
-		db, _      = ethdb.NewMemDatabase()
+		db         = ethdb.NewMemDatabase()
 		txFeed     = new(event.Feed)
 		rmLogsFeed = new(event.Feed)
 		logsFeed   = new(event.Feed)
@@ -471,7 +471,7 @@ func TestPendingLogsSubscription(t *testing.T) {
 
 	var (
 		mux        = new(event.TypeMux)
-		db, _      = ethdb.NewMemDatabase()
+		db         = ethdb.NewMemDatabase()
 		txFeed     = new(event.Feed)
 		rmLogsFeed = new(event.Feed)
 		logsFeed   = new(event.Feed)
diff --git a/eth/handler_test.go b/eth/handler_test.go
index e336dfa2857a..fee4114eb6bf 100644
--- a/eth/handler_test.go
+++ b/eth/handler_test.go
@@ -366,7 +366,7 @@ func testGetNodeData(t *testing.T, protocol int) {
 			t.Errorf("data hash mismatch: have %x, want %x", hash, want)
 		}
 	}
-	statedb, _ := ethdb.NewMemDatabase()
+	statedb := ethdb.NewMemDatabase()
 	for i := 0; i < len(data); i++ {
 		statedb.Put(hashes[i].Bytes(), data[i])
 	}
@@ -468,7 +468,7 @@ func testDAOChallenge(t *testing.T, localForked, remoteForked bool, timeout bool
 	var (
 		evmux         = new(event.TypeMux)
 		pow           = ethash.NewFaker()
-		db, _         = ethdb.NewMemDatabase()
+		db            = ethdb.NewMemDatabase()
 		config        = &params.ChainConfig{DAOForkBlock: big.NewInt(1), DAOForkSupport: localForked}
 		gspec         = &core.Genesis{Config: config}
 		genesis       = gspec.MustCommit(db)
diff --git a/eth/helper_test.go b/eth/helper_test.go
index 2b05cea801a0..8a0260fc951b 100644
--- a/eth/helper_test.go
+++ b/eth/helper_test.go
@@ -53,7 +53,7 @@ func newTestProtocolManager(mode downloader.SyncMode, blocks int, generator func
 	var (
 		evmux  = new(event.TypeMux)
 		engine = ethash.NewFaker()
-		db, _  = ethdb.NewMemDatabase()
+		db     = ethdb.NewMemDatabase()
 		gspec  = &core.Genesis{
 			Config: params.TestChainConfig,
 			Alloc:  core.GenesisAlloc{testBank: {Balance: big.NewInt(1000000)}},
diff --git a/eth/tracers/tracers_test.go b/eth/tracers/tracers_test.go
index bf8120228fb0..a58ef1af3380 100644
--- a/eth/tracers/tracers_test.go
+++ b/eth/tracers/tracers_test.go
@@ -159,7 +159,7 @@ func TestCallTracer(t *testing.T) {
 				GasLimit:    uint64(test.Context.GasLimit),
 				GasPrice:    tx.GasPrice(),
 			}
-			db, _ := ethdb.NewMemDatabase()
+			db := ethdb.NewMemDatabase()
 			statedb := tests.MakePreState(db, test.Genesis.Alloc)
 
 			// Create the tracer, the EVM environment and run it
diff --git a/ethdb/database_test.go b/ethdb/database_test.go
index 5e4a3ca34a8e..bc680ff93887 100644
--- a/ethdb/database_test.go
+++ b/ethdb/database_test.go
@@ -53,7 +53,7 @@ func TestLDB_PutGet(t *testing.T) {
 }
 
 func TestMemoryDB_PutGet(t *testing.T) {
-	db, _ := ethdb.NewMemDatabase()
+	db := ethdb.NewMemDatabase()
 	testPutGet(db, t)
 }
 
@@ -131,7 +131,7 @@ func TestLDB_ParallelPutGet(t *testing.T) {
 }
 
 func TestMemoryDB_ParallelPutGet(t *testing.T) {
-	db, _ := ethdb.NewMemDatabase()
+	db := ethdb.NewMemDatabase()
 	testParallelPutGet(db, t)
 }
 
diff --git a/ethdb/memory_database.go b/ethdb/memory_database.go
index 8efd7bf8458e..c57042920af4 100644
--- a/ethdb/memory_database.go
+++ b/ethdb/memory_database.go
@@ -31,16 +31,16 @@ type MemDatabase struct {
 	lock sync.RWMutex
 }
 
-func NewMemDatabase() (*MemDatabase, error) {
+func NewMemDatabase() *MemDatabase {
 	return &MemDatabase{
 		db: make(map[string][]byte),
-	}, nil
+	}
 }
 
-func NewMemDatabaseWithCap(size int) (*MemDatabase, error) {
+func NewMemDatabaseWithCap(size int) *MemDatabase {
 	return &MemDatabase{
 		db: make(map[string][]byte, size),
-	}, nil
+	}
 }
 
 func (db *MemDatabase) Put(key []byte, value []byte) error {
diff --git a/les/handler_test.go b/les/handler_test.go
index fa38d1d4f7cd..d24b2c66599a 100644
--- a/les/handler_test.go
+++ b/les/handler_test.go
@@ -51,7 +51,7 @@ func TestGetBlockHeadersLes1(t *testing.T) { testGetBlockHeaders(t, 1) }
 func TestGetBlockHeadersLes2(t *testing.T) { testGetBlockHeaders(t, 2) }
 
 func testGetBlockHeaders(t *testing.T, protocol int) {
-	db, _ := ethdb.NewMemDatabase()
+	db := ethdb.NewMemDatabase()
 	pm := newTestProtocolManagerMust(t, false, downloader.MaxHashFetch+15, nil, nil, nil, db)
 	bc := pm.blockchain.(*core.BlockChain)
 	peer, _ := newTestPeer(t, "peer", protocol, pm, true)
@@ -181,7 +181,7 @@ func TestGetBlockBodiesLes1(t *testing.T) { testGetBlockBodies(t, 1) }
 func TestGetBlockBodiesLes2(t *testing.T) { testGetBlockBodies(t, 2) }
 
 func testGetBlockBodies(t *testing.T, protocol int) {
-	db, _ := ethdb.NewMemDatabase()
+	db := ethdb.NewMemDatabase()
 	pm := newTestProtocolManagerMust(t, false, downloader.MaxBlockFetch+15, nil, nil, nil, db)
 	bc := pm.blockchain.(*core.BlockChain)
 	peer, _ := newTestPeer(t, "peer", protocol, pm, true)
@@ -259,7 +259,7 @@ func TestGetCodeLes2(t *testing.T) { testGetCode(t, 2) }
 
 func testGetCode(t *testing.T, protocol int) {
 	// Assemble the test environment
-	db, _ := ethdb.NewMemDatabase()
+	db := ethdb.NewMemDatabase()
 	pm := newTestProtocolManagerMust(t, false, 4, testChainGen, nil, nil, db)
 	bc := pm.blockchain.(*core.BlockChain)
 	peer, _ := newTestPeer(t, "peer", protocol, pm, true)
@@ -293,7 +293,7 @@ func TestGetReceiptLes2(t *testing.T) { testGetReceipt(t, 2) }
 
 func testGetReceipt(t *testing.T, protocol int) {
 	// Assemble the test environment
-	db, _ := ethdb.NewMemDatabase()
+	db := ethdb.NewMemDatabase()
 	pm := newTestProtocolManagerMust(t, false, 4, testChainGen, nil, nil, db)
 	bc := pm.blockchain.(*core.BlockChain)
 	peer, _ := newTestPeer(t, "peer", protocol, pm, true)
@@ -321,7 +321,7 @@ func TestGetProofsLes2(t *testing.T) { testGetProofs(t, 2) }
 
 func testGetProofs(t *testing.T, protocol int) {
 	// Assemble the test environment
-	db, _ := ethdb.NewMemDatabase()
+	db := ethdb.NewMemDatabase()
 	pm := newTestProtocolManagerMust(t, false, 4, testChainGen, nil, nil, db)
 	bc := pm.blockchain.(*core.BlockChain)
 	peer, _ := newTestPeer(t, "peer", protocol, pm, true)
@@ -384,7 +384,7 @@ func testGetCHTProofs(t *testing.T, protocol int) {
 		frequency = uint64(light.CHTFrequencyServer)
 	}
 	// Assemble the test environment
-	db, _ := ethdb.NewMemDatabase()
+	db := ethdb.NewMemDatabase()
 	pm := newTestProtocolManagerMust(t, false, int(frequency)+light.HelperTrieProcessConfirmations, testChainGen, nil, nil, db)
 	bc := pm.blockchain.(*core.BlockChain)
 	peer, _ := newTestPeer(t, "peer", protocol, pm, true)
@@ -452,7 +452,7 @@ func testGetCHTProofs(t *testing.T, protocol int) {
 // Tests that bloombits proofs can be correctly retrieved.
 func TestGetBloombitsProofs(t *testing.T) {
 	// Assemble the test environment
-	db, _ := ethdb.NewMemDatabase()
+	db := ethdb.NewMemDatabase()
 	pm := newTestProtocolManagerMust(t, false, light.BloomTrieFrequency+256, testChainGen, nil, nil, db)
 	bc := pm.blockchain.(*core.BlockChain)
 	peer, _ := newTestPeer(t, "peer", 2, pm, true)
@@ -491,7 +491,7 @@ func TestGetBloombitsProofs(t *testing.T) {
 }
 
 func TestTransactionStatusLes2(t *testing.T) {
-	db, _ := ethdb.NewMemDatabase()
+	db := ethdb.NewMemDatabase()
 	pm := newTestProtocolManagerMust(t, false, 0, nil, nil, nil, db)
 	chain := pm.blockchain.(*core.BlockChain)
 	config := core.DefaultTxPoolConfig
diff --git a/les/odr_test.go b/les/odr_test.go
index 9973df043097..983f7262b06a 100644
--- a/les/odr_test.go
+++ b/les/odr_test.go
@@ -165,8 +165,8 @@ func testOdr(t *testing.T, protocol int, expFail uint64, fn odrTestFn) {
 	peers := newPeerSet()
 	dist := newRequestDistributor(peers, make(chan struct{}))
 	rm := newRetrieveManager(peers, dist, nil)
-	db, _ := ethdb.NewMemDatabase()
-	ldb, _ := ethdb.NewMemDatabase()
+	db := ethdb.NewMemDatabase()
+	ldb := ethdb.NewMemDatabase()
 	odr := NewLesOdr(ldb, light.NewChtIndexer(db, true), light.NewBloomTrieIndexer(db, true), eth.NewBloomIndexer(db, light.BloomTrieFrequency), rm)
 	pm := newTestProtocolManagerMust(t, false, 4, testChainGen, nil, nil, db)
 	lpm := newTestProtocolManagerMust(t, true, 0, nil, peers, odr, ldb)
diff --git a/les/request_test.go b/les/request_test.go
index d4282a592749..ba2f603d8b4a 100644
--- a/les/request_test.go
+++ b/les/request_test.go
@@ -87,8 +87,8 @@ func testAccess(t *testing.T, protocol int, fn accessTestFn) {
 	peers := newPeerSet()
 	dist := newRequestDistributor(peers, make(chan struct{}))
 	rm := newRetrieveManager(peers, dist, nil)
-	db, _ := ethdb.NewMemDatabase()
-	ldb, _ := ethdb.NewMemDatabase()
+	db := ethdb.NewMemDatabase()
+	ldb := ethdb.NewMemDatabase()
 	odr := NewLesOdr(ldb, light.NewChtIndexer(db, true), light.NewBloomTrieIndexer(db, true), eth.NewBloomIndexer(db, light.BloomTrieFrequency), rm)
 
 	pm := newTestProtocolManagerMust(t, false, 4, testChainGen, nil, nil, db)
diff --git a/light/lightchain_test.go b/light/lightchain_test.go
index b8ab1c51cfc3..c0aa51da290d 100644
--- a/light/lightchain_test.go
+++ b/light/lightchain_test.go
@@ -52,7 +52,7 @@ func makeHeaderChain(parent *types.Header, n int, db ethdb.Database, seed int) [
 // chain. Depending on the full flag, if creates either a full block chain or a
 // header only chain.
 func newCanonical(n int) (ethdb.Database, *LightChain, error) {
-	db, _ := ethdb.NewMemDatabase()
+	db := ethdb.NewMemDatabase()
 	gspec := core.Genesis{Config: params.TestChainConfig}
 	genesis := gspec.MustCommit(db)
 	blockchain, _ := NewLightChain(&dummyOdr{db: db}, gspec.Config, ethash.NewFaker())
@@ -69,7 +69,7 @@ func newCanonical(n int) (ethdb.Database, *LightChain, error) {
 
 // newTestLightChain creates a LightChain that doesn't validate anything.
 func newTestLightChain() *LightChain {
-	db, _ := ethdb.NewMemDatabase()
+	db := ethdb.NewMemDatabase()
 	gspec := &core.Genesis{
 		Difficulty: big.NewInt(1),
 		Config:     params.TestChainConfig,
diff --git a/light/odr_test.go b/light/odr_test.go
index cc7475df38fb..3e7ac1011830 100644
--- a/light/odr_test.go
+++ b/light/odr_test.go
@@ -245,8 +245,8 @@ func testChainGen(i int, block *core.BlockGen) {
 
 func testChainOdr(t *testing.T, protocol int, fn odrTestFn) {
 	var (
-		sdb, _  = ethdb.NewMemDatabase()
-		ldb, _  = ethdb.NewMemDatabase()
+		sdb     = ethdb.NewMemDatabase()
+		ldb     = ethdb.NewMemDatabase()
 		gspec   = core.Genesis{Alloc: core.GenesisAlloc{testBankAddress: {Balance: testBankFunds}}}
 		genesis = gspec.MustCommit(sdb)
 	)
diff --git a/light/trie_test.go b/light/trie_test.go
index 0d6b2cc1d8dd..84c6f162fb73 100644
--- a/light/trie_test.go
+++ b/light/trie_test.go
@@ -34,10 +34,10 @@ import (
 
 func TestNodeIterator(t *testing.T) {
 	var (
-		fulldb, _  = ethdb.NewMemDatabase()
-		lightdb, _ = ethdb.NewMemDatabase()
-		gspec      = core.Genesis{Alloc: core.GenesisAlloc{testBankAddress: {Balance: testBankFunds}}}
-		genesis    = gspec.MustCommit(fulldb)
+		fulldb  = ethdb.NewMemDatabase()
+		lightdb = ethdb.NewMemDatabase()
+		gspec   = core.Genesis{Alloc: core.GenesisAlloc{testBankAddress: {Balance: testBankFunds}}}
+		genesis = gspec.MustCommit(fulldb)
 	)
 	gspec.MustCommit(lightdb)
 	blockchain, _ := core.NewBlockChain(fulldb, nil, params.TestChainConfig, ethash.NewFullFaker(), vm.Config{})
diff --git a/light/txpool_test.go b/light/txpool_test.go
index 13d7d3cebbb1..ccbd83a94306 100644
--- a/light/txpool_test.go
+++ b/light/txpool_test.go
@@ -81,8 +81,8 @@ func TestTxPool(t *testing.T) {
 	}
 
 	var (
-		sdb, _  = ethdb.NewMemDatabase()
-		ldb, _  = ethdb.NewMemDatabase()
+		sdb     = ethdb.NewMemDatabase()
+		ldb     = ethdb.NewMemDatabase()
 		gspec   = core.Genesis{Alloc: core.GenesisAlloc{testBankAddress: {Balance: testBankFunds}}}
 		genesis = gspec.MustCommit(sdb)
 	)
diff --git a/node/node.go b/node/node.go
index 83b6c4c07e6c..c4368189f7be 100644
--- a/node/node.go
+++ b/node/node.go
@@ -568,7 +568,7 @@ func (n *Node) EventMux() *event.TypeMux {
 // ephemeral, a memory database is returned.
 func (n *Node) OpenDatabase(name string, cache, handles int) (ethdb.Database, error) {
 	if n.config.DataDir == "" {
-		return ethdb.NewMemDatabase()
+		return ethdb.NewMemDatabase(), nil
 	}
 	return ethdb.NewLDBDatabase(n.config.resolvePath(name), cache, handles)
 }
diff --git a/node/service.go b/node/service.go
index 55062a500454..afc43e8486cb 100644
--- a/node/service.go
+++ b/node/service.go
@@ -41,7 +41,7 @@ type ServiceContext struct {
 // node is an ephemeral one, a memory database is returned.
 func (ctx *ServiceContext) OpenDatabase(name string, cache int, handles int) (ethdb.Database, error) {
 	if ctx.config.DataDir == "" {
-		return ethdb.NewMemDatabase()
+		return ethdb.NewMemDatabase(), nil
 	}
 	db, err := ethdb.NewLDBDatabase(ctx.config.resolvePath(name), cache, handles)
 	if err != nil {
diff --git a/tests/block_test_util.go b/tests/block_test_util.go
index 579e783b1011..a72799f6e2c9 100644
--- a/tests/block_test_util.go
+++ b/tests/block_test_util.go
@@ -98,7 +98,7 @@ func (t *BlockTest) Run() error {
 	}
 
 	// import pre accounts & construct test genesis block & state root
-	db, _ := ethdb.NewMemDatabase()
+	db := ethdb.NewMemDatabase()
 	gblock, err := t.genesis(config).Commit(db)
 	if err != nil {
 		return err
diff --git a/tests/state_test_util.go b/tests/state_test_util.go
index 3b761bd771b5..ff71e0eb917a 100644
--- a/tests/state_test_util.go
+++ b/tests/state_test_util.go
@@ -126,7 +126,7 @@ func (t *StateTest) Run(subtest StateSubtest, vmconfig vm.Config) (*state.StateD
 		return nil, UnsupportedForkError{subtest.Fork}
 	}
 	block := t.genesis(config).ToBlock(nil)
-	db, _ := ethdb.NewMemDatabase()
+	db := ethdb.NewMemDatabase()
 	statedb := MakePreState(db, t.json.Pre)
 
 	post := t.json.Post[subtest.Fork][subtest.Index]
diff --git a/tests/vm_test_util.go b/tests/vm_test_util.go
index b365167a6975..c9cc4a59ef11 100644
--- a/tests/vm_test_util.go
+++ b/tests/vm_test_util.go
@@ -79,7 +79,7 @@ type vmExecMarshaling struct {
 }
 
 func (t *VMTest) Run(vmconfig vm.Config) error {
-	db, _ := ethdb.NewMemDatabase()
+	db := ethdb.NewMemDatabase()
 	statedb := MakePreState(db, t.json.Pre)
 	ret, gasRemaining, err := t.exec(statedb, vmconfig)
 
diff --git a/trie/iterator_test.go b/trie/iterator_test.go
index dce1c78b5d0c..2a510b1c2ddd 100644
--- a/trie/iterator_test.go
+++ b/trie/iterator_test.go
@@ -289,7 +289,7 @@ func TestIteratorContinueAfterErrorDisk(t *testing.T)    { testIteratorContinueA
 func TestIteratorContinueAfterErrorMemonly(t *testing.T) { testIteratorContinueAfterError(t, true) }
 
 func testIteratorContinueAfterError(t *testing.T, memonly bool) {
-	diskdb, _ := ethdb.NewMemDatabase()
+	diskdb := ethdb.NewMemDatabase()
 	triedb := NewDatabase(diskdb)
 
 	tr, _ := New(common.Hash{}, triedb)
@@ -376,7 +376,7 @@ func TestIteratorContinueAfterSeekErrorMemonly(t *testing.T) {
 
 func testIteratorContinueAfterSeekError(t *testing.T, memonly bool) {
 	// Commit test trie to db, then remove the node containing "bars".
-	diskdb, _ := ethdb.NewMemDatabase()
+	diskdb := ethdb.NewMemDatabase()
 	triedb := NewDatabase(diskdb)
 
 	ctr, _ := New(common.Hash{}, triedb)
diff --git a/trie/proof_test.go b/trie/proof_test.go
index fff313d7fdfb..a3537787cc09 100644
--- a/trie/proof_test.go
+++ b/trie/proof_test.go
@@ -36,7 +36,7 @@ func TestProof(t *testing.T) {
 	trie, vals := randomTrie(500)
 	root := trie.Hash()
 	for _, kv := range vals {
-		proofs, _ := ethdb.NewMemDatabase()
+		proofs := ethdb.NewMemDatabase()
 		if trie.Prove(kv.k, 0, proofs) != nil {
 			t.Fatalf("missing key %x while constructing proof", kv.k)
 		}
@@ -53,7 +53,7 @@ func TestProof(t *testing.T) {
 func TestOneElementProof(t *testing.T) {
 	trie := new(Trie)
 	updateString(trie, "k", "v")
-	proofs, _ := ethdb.NewMemDatabase()
+	proofs := ethdb.NewMemDatabase()
 	trie.Prove([]byte("k"), 0, proofs)
 	if len(proofs.Keys()) != 1 {
 		t.Error("proof should have one element")
@@ -71,7 +71,7 @@ func TestVerifyBadProof(t *testing.T) {
 	trie, vals := randomTrie(800)
 	root := trie.Hash()
 	for _, kv := range vals {
-		proofs, _ := ethdb.NewMemDatabase()
+		proofs := ethdb.NewMemDatabase()
 		trie.Prove(kv.k, 0, proofs)
 		if len(proofs.Keys()) == 0 {
 			t.Fatal("zero length proof")
@@ -109,7 +109,7 @@ func BenchmarkProve(b *testing.B) {
 	b.ResetTimer()
 	for i := 0; i < b.N; i++ {
 		kv := vals[keys[i%len(keys)]]
-		proofs, _ := ethdb.NewMemDatabase()
+		proofs := ethdb.NewMemDatabase()
 		if trie.Prove(kv.k, 0, proofs); len(proofs.Keys()) == 0 {
 			b.Fatalf("zero length proof for %x", kv.k)
 		}
@@ -123,7 +123,7 @@ func BenchmarkVerifyProof(b *testing.B) {
 	var proofs []*ethdb.MemDatabase
 	for k := range vals {
 		keys = append(keys, k)
-		proof, _ := ethdb.NewMemDatabase()
+		proof := ethdb.NewMemDatabase()
 		trie.Prove([]byte(k), 0, proof)
 		proofs = append(proofs, proof)
 	}
diff --git a/trie/secure_trie_test.go b/trie/secure_trie_test.go
index aedf5a1cde0e..85173d116fc7 100644
--- a/trie/secure_trie_test.go
+++ b/trie/secure_trie_test.go
@@ -28,7 +28,7 @@ import (
 )
 
 func newEmptySecure() *SecureTrie {
-	diskdb, _ := ethdb.NewMemDatabase()
+	diskdb := ethdb.NewMemDatabase()
 	triedb := NewDatabase(diskdb)
 
 	trie, _ := NewSecure(common.Hash{}, triedb, 0)
@@ -38,7 +38,7 @@ func newEmptySecure() *SecureTrie {
 // makeTestSecureTrie creates a large enough secure trie for testing.
 func makeTestSecureTrie() (*Database, *SecureTrie, map[string][]byte) {
 	// Create an empty trie
-	diskdb, _ := ethdb.NewMemDatabase()
+	diskdb := ethdb.NewMemDatabase()
 	triedb := NewDatabase(diskdb)
 
 	trie, _ := NewSecure(common.Hash{}, triedb, 0)
diff --git a/trie/sync_test.go b/trie/sync_test.go
index 4a720612b646..505d79f25bc7 100644
--- a/trie/sync_test.go
+++ b/trie/sync_test.go
@@ -27,7 +27,7 @@ import (
 // makeTestTrie create a sample test trie to test node-wise reconstruction.
 func makeTestTrie() (*Database, *Trie, map[string][]byte) {
 	// Create an empty trie
-	diskdb, _ := ethdb.NewMemDatabase()
+	diskdb := ethdb.NewMemDatabase()
 	triedb := NewDatabase(diskdb)
 	trie, _ := New(common.Hash{}, triedb)
 
@@ -89,17 +89,17 @@ func checkTrieConsistency(db *Database, root common.Hash) error {
 
 // Tests that an empty trie is not scheduled for syncing.
 func TestEmptyTrieSync(t *testing.T) {
-	diskdbA, _ := ethdb.NewMemDatabase()
+	diskdbA := ethdb.NewMemDatabase()
 	triedbA := NewDatabase(diskdbA)
 
-	diskdbB, _ := ethdb.NewMemDatabase()
+	diskdbB := ethdb.NewMemDatabase()
 	triedbB := NewDatabase(diskdbB)
 
 	emptyA, _ := New(common.Hash{}, triedbA)
 	emptyB, _ := New(emptyRoot, triedbB)
 
 	for i, trie := range []*Trie{emptyA, emptyB} {
-		diskdb, _ := ethdb.NewMemDatabase()
+		diskdb := ethdb.NewMemDatabase()
 		if req := NewTrieSync(trie.Hash(), diskdb, nil).Missing(1); len(req) != 0 {
 			t.Errorf("test %d: content requested for empty trie: %v", i, req)
 		}
@@ -116,7 +116,7 @@ func testIterativeTrieSync(t *testing.T, batch int) {
 	srcDb, srcTrie, srcData := makeTestTrie()
 
 	// Create a destination trie and sync with the scheduler
-	diskdb, _ := ethdb.NewMemDatabase()
+	diskdb := ethdb.NewMemDatabase()
 	triedb := NewDatabase(diskdb)
 	sched := NewTrieSync(srcTrie.Hash(), diskdb, nil)
 
@@ -149,7 +149,7 @@ func TestIterativeDelayedTrieSync(t *testing.T) {
 	srcDb, srcTrie, srcData := makeTestTrie()
 
 	// Create a destination trie and sync with the scheduler
-	diskdb, _ := ethdb.NewMemDatabase()
+	diskdb := ethdb.NewMemDatabase()
 	triedb := NewDatabase(diskdb)
 	sched := NewTrieSync(srcTrie.Hash(), diskdb, nil)
 
@@ -187,7 +187,7 @@ func testIterativeRandomTrieSync(t *testing.T, batch int) {
 	srcDb, srcTrie, srcData := makeTestTrie()
 
 	// Create a destination trie and sync with the scheduler
-	diskdb, _ := ethdb.NewMemDatabase()
+	diskdb := ethdb.NewMemDatabase()
 	triedb := NewDatabase(diskdb)
 	sched := NewTrieSync(srcTrie.Hash(), diskdb, nil)
 
@@ -228,7 +228,7 @@ func TestIterativeRandomDelayedTrieSync(t *testing.T) {
 	srcDb, srcTrie, srcData := makeTestTrie()
 
 	// Create a destination trie and sync with the scheduler
-	diskdb, _ := ethdb.NewMemDatabase()
+	diskdb := ethdb.NewMemDatabase()
 	triedb := NewDatabase(diskdb)
 	sched := NewTrieSync(srcTrie.Hash(), diskdb, nil)
 
@@ -275,7 +275,7 @@ func TestDuplicateAvoidanceTrieSync(t *testing.T) {
 	srcDb, srcTrie, srcData := makeTestTrie()
 
 	// Create a destination trie and sync with the scheduler
-	diskdb, _ := ethdb.NewMemDatabase()
+	diskdb := ethdb.NewMemDatabase()
 	triedb := NewDatabase(diskdb)
 	sched := NewTrieSync(srcTrie.Hash(), diskdb, nil)
 
@@ -315,7 +315,7 @@ func TestIncompleteTrieSync(t *testing.T) {
 	srcDb, srcTrie, _ := makeTestTrie()
 
 	// Create a destination trie and sync with the scheduler
-	diskdb, _ := ethdb.NewMemDatabase()
+	diskdb := ethdb.NewMemDatabase()
 	triedb := NewDatabase(diskdb)
 	sched := NewTrieSync(srcTrie.Hash(), diskdb, nil)
 
diff --git a/trie/trie_test.go b/trie/trie_test.go
index 997222628898..1a4e3385b9fd 100644
--- a/trie/trie_test.go
+++ b/trie/trie_test.go
@@ -43,7 +43,7 @@ func init() {
 
 // Used for testing
 func newEmpty() *Trie {
-	diskdb, _ := ethdb.NewMemDatabase()
+	diskdb := ethdb.NewMemDatabase()
 	trie, _ := New(common.Hash{}, NewDatabase(diskdb))
 	return trie
 }
@@ -68,7 +68,7 @@ func TestNull(t *testing.T) {
 }
 
 func TestMissingRoot(t *testing.T) {
-	diskdb, _ := ethdb.NewMemDatabase()
+	diskdb := ethdb.NewMemDatabase()
 	trie, err := New(common.HexToHash("0beec7b5ea3f0fdbc95d0dd47f3c5bc275da8a33"), NewDatabase(diskdb))
 	if trie != nil {
 		t.Error("New returned non-nil trie for invalid root")
@@ -82,7 +82,7 @@ func TestMissingNodeDisk(t *testing.T)    { testMissingNode(t, false) }
 func TestMissingNodeMemonly(t *testing.T) { testMissingNode(t, true) }
 
 func testMissingNode(t *testing.T, memonly bool) {
-	diskdb, _ := ethdb.NewMemDatabase()
+	diskdb := ethdb.NewMemDatabase()
 	triedb := NewDatabase(diskdb)
 
 	trie, _ := New(common.Hash{}, triedb)
@@ -413,7 +413,7 @@ func (randTest) Generate(r *rand.Rand, size int) reflect.Value {
 }
 
 func runRandTest(rt randTest) bool {
-	diskdb, _ := ethdb.NewMemDatabase()
+	diskdb := ethdb.NewMemDatabase()
 	triedb := NewDatabase(diskdb)
 
 	tr, _ := New(common.Hash{}, triedb)

From 76e01aa6e7c2e24a00d4980fae1241facf8cc8e4 Mon Sep 17 00:00:00 2001
From: rjl493456442 <garyrong0905@gmail.com>
Date: Wed, 9 May 2018 18:34:22 +0800
Subject: [PATCH 2/3] core: clean up variables definition

---
 core/chain_makers.go | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/core/chain_makers.go b/core/chain_makers.go
index 3fb2ecbd92fd..fcba90bb87d7 100644
--- a/core/chain_makers.go
+++ b/core/chain_makers.go
@@ -256,11 +256,12 @@ func makeHeader(chain consensus.ChainReader, parent *types.Block, state *state.S
 // chain. Depending on the full flag, if creates either a full block chain or a
 // header only chain.
 func newCanonical(engine consensus.Engine, n int, full bool) (ethdb.Database, *BlockChain, error) {
-	// Initialize a fresh chain with only a genesis block
-	gspec := new(Genesis)
-	db := ethdb.NewMemDatabase()
-	genesis := gspec.MustCommit(db)
+	var (
+		db      = ethdb.NewMemDatabase()
+		genesis = new(Genesis).MustCommit(db)
+	)
 
+	// Initialize a fresh chain with only a genesis block
 	blockchain, _ := NewBlockChain(db, nil, params.AllEthashProtocolChanges, engine, vm.Config{})
 	// Create and inject the requested chain
 	if n == 0 {

From a080dcf356ec5e8b135863ed11f5ca37f7d488ad Mon Sep 17 00:00:00 2001
From: rjl493456442 <garyrong0905@gmail.com>
Date: Wed, 9 May 2018 19:18:25 +0800
Subject: [PATCH 3/3] all: inline mdb definition

---
 cmd/evm/runner.go                |  3 +-
 core/helper_test.go              |  5 +--
 core/state/managed_state_test.go |  3 +-
 core/state/state_test.go         |  3 +-
 core/state/statedb_test.go       |  9 ++----
 core/state/sync_test.go          |  6 ++--
 core/tx_pool_test.go             | 54 +++++++++++---------------------
 core/vm/runtime/runtime.go       |  6 ++--
 core/vm/runtime/runtime_test.go  |  3 +-
 eth/api_test.go                  |  3 +-
 eth/tracers/tracers_test.go      |  3 +-
 ethdb/database_test.go           |  6 ++--
 les/handler_test.go              |  9 ++----
 tests/state_test_util.go         |  3 +-
 tests/vm_test_util.go            |  3 +-
 trie/secure_trie_test.go         |  8 ++---
 trie/sync_test.go                | 18 ++++-------
 trie/trie_test.go                |  9 ++----
 18 files changed, 50 insertions(+), 104 deletions(-)

diff --git a/cmd/evm/runner.go b/cmd/evm/runner.go
index ef1a96f6dbea..7138a9ddd439 100644
--- a/cmd/evm/runner.go
+++ b/cmd/evm/runner.go
@@ -104,8 +104,7 @@ func runCmd(ctx *cli.Context) error {
 		chainConfig = gen.Config
 		blockNumber = gen.Number
 	} else {
-		db := ethdb.NewMemDatabase()
-		statedb, _ = state.New(common.Hash{}, state.NewDatabase(db))
+		statedb, _ = state.New(common.Hash{}, state.NewDatabase(ethdb.NewMemDatabase()))
 	}
 	if ctx.GlobalString(SenderFlag.Name) != "" {
 		sender = common.HexToAddress(ctx.GlobalString(SenderFlag.Name))
diff --git a/core/helper_test.go b/core/helper_test.go
index 00e67de2778e..051384d8547b 100644
--- a/core/helper_test.go
+++ b/core/helper_test.go
@@ -76,14 +76,11 @@ func (tm *TestManager) Db() ethdb.Database {
 }
 
 func NewTestManager() *TestManager {
-	db := ethdb.NewMemDatabase()
-
 	testManager := &TestManager{}
 	testManager.eventMux = new(event.TypeMux)
-	testManager.db = db
+	testManager.db = ethdb.NewMemDatabase()
 	// testManager.txPool = NewTxPool(testManager)
 	// testManager.blockChain = NewBlockChain(testManager)
 	// testManager.stateManager = NewStateManager(testManager)
-
 	return testManager
 }
diff --git a/core/state/managed_state_test.go b/core/state/managed_state_test.go
index ebe796bc0185..3d9c4e867603 100644
--- a/core/state/managed_state_test.go
+++ b/core/state/managed_state_test.go
@@ -26,8 +26,7 @@ import (
 var addr = common.BytesToAddress([]byte("test"))
 
 func create() (*ManagedState, *account) {
-	db := ethdb.NewMemDatabase()
-	statedb, _ := New(common.Hash{}, NewDatabase(db))
+	statedb, _ := New(common.Hash{}, NewDatabase(ethdb.NewMemDatabase()))
 	ms := ManageState(statedb)
 	ms.StateDB.SetNonce(addr, 100)
 	ms.accounts[addr] = newAccount(ms.StateDB.getStateObject(addr))
diff --git a/core/state/state_test.go b/core/state/state_test.go
index 8c7412c1ceba..12778f6f129d 100644
--- a/core/state/state_test.go
+++ b/core/state/state_test.go
@@ -133,8 +133,7 @@ func (s *StateSuite) TestSnapshotEmpty(c *checker.C) {
 // use testing instead of checker because checker does not support
 // printing/logging in tests (-check.vv does not work)
 func TestSnapshot2(t *testing.T) {
-	db := ethdb.NewMemDatabase()
-	state, _ := New(common.Hash{}, NewDatabase(db))
+	state, _ := New(common.Hash{}, NewDatabase(ethdb.NewMemDatabase()))
 
 	stateobjaddr0 := toAddr([]byte("so0"))
 	stateobjaddr1 := toAddr([]byte("so1"))
diff --git a/core/state/statedb_test.go b/core/state/statedb_test.go
index 9a103aa3c18c..e2b349de86c1 100644
--- a/core/state/statedb_test.go
+++ b/core/state/statedb_test.go
@@ -122,8 +122,7 @@ func TestIntermediateLeaks(t *testing.T) {
 // https://github.com/ethereum/go-ethereum/pull/15549.
 func TestCopy(t *testing.T) {
 	// Create a random state test to copy and modify "independently"
-	db := ethdb.NewMemDatabase()
-	orig, _ := New(common.Hash{}, NewDatabase(db))
+	orig, _ := New(common.Hash{}, NewDatabase(ethdb.NewMemDatabase()))
 
 	for i := byte(0); i < 255; i++ {
 		obj := orig.GetOrNewStateObject(common.BytesToAddress([]byte{i}))
@@ -334,8 +333,7 @@ func (test *snapshotTest) String() string {
 func (test *snapshotTest) run() bool {
 	// Run all actions and create snapshots.
 	var (
-		db           = ethdb.NewMemDatabase()
-		state, _     = New(common.Hash{}, NewDatabase(db))
+		state, _     = New(common.Hash{}, NewDatabase(ethdb.NewMemDatabase()))
 		snapshotRevs = make([]int, len(test.snapshots))
 		sindex       = 0
 	)
@@ -426,8 +424,7 @@ func (s *StateSuite) TestTouchDelete(c *check.C) {
 // TestCopyOfCopy tests that modified objects are carried over to the copy, and the copy of the copy.
 // See https://github.com/ethereum/go-ethereum/pull/15225#issuecomment-380191512
 func TestCopyOfCopy(t *testing.T) {
-	db := ethdb.NewMemDatabase()
-	sdb, _ := New(common.Hash{}, NewDatabase(db))
+	sdb, _ := New(common.Hash{}, NewDatabase(ethdb.NewMemDatabase()))
 	addr := common.HexToAddress("aaaa")
 	sdb.SetBalance(addr, big.NewInt(42))
 
diff --git a/core/state/sync_test.go b/core/state/sync_test.go
index 6ec26d233444..31774016082a 100644
--- a/core/state/sync_test.go
+++ b/core/state/sync_test.go
@@ -38,8 +38,7 @@ type testAccount struct {
 // makeTestState create a sample test state to test node-wise reconstruction.
 func makeTestState() (Database, common.Hash, []*testAccount) {
 	// Create an empty state
-	diskdb := ethdb.NewMemDatabase()
-	db := NewDatabase(diskdb)
+	db := NewDatabase(ethdb.NewMemDatabase())
 	state, _ := New(common.Hash{}, db)
 
 	// Fill it with some arbitrary data
@@ -125,8 +124,7 @@ func checkStateConsistency(db ethdb.Database, root common.Hash) error {
 // Tests that an empty state is not scheduled for syncing.
 func TestEmptyStateSync(t *testing.T) {
 	empty := common.HexToHash("56e81f171bcc55a6ff8345e692c0f86e5b48e01b996cadc001622fb5e363b421")
-	db := ethdb.NewMemDatabase()
-	if req := NewStateSync(empty, db).Missing(1); len(req) != 0 {
+	if req := NewStateSync(empty, ethdb.NewMemDatabase()).Missing(1); len(req) != 0 {
 		t.Errorf("content requested for empty state: %v", req)
 	}
 }
diff --git a/core/tx_pool_test.go b/core/tx_pool_test.go
index 48104164730a..e7f52075e556 100644
--- a/core/tx_pool_test.go
+++ b/core/tx_pool_test.go
@@ -78,8 +78,7 @@ func pricedTransaction(nonce uint64, gaslimit uint64, gasprice *big.Int, key *ec
 }
 
 func setupTxPool() (*TxPool, *ecdsa.PrivateKey) {
-	diskdb := ethdb.NewMemDatabase()
-	statedb, _ := state.New(common.Hash{}, state.NewDatabase(diskdb))
+	statedb, _ := state.New(common.Hash{}, state.NewDatabase(ethdb.NewMemDatabase()))
 	blockchain := &testBlockChain{statedb, 1000000, new(event.Feed)}
 
 	key, _ := crypto.GenerateKey()
@@ -158,8 +157,7 @@ func (c *testChain) State() (*state.StateDB, error) {
 	// a state change between those fetches.
 	stdb := c.statedb
 	if *c.trigger {
-		db := ethdb.NewMemDatabase()
-		c.statedb, _ = state.New(common.Hash{}, state.NewDatabase(db))
+		c.statedb, _ = state.New(common.Hash{}, state.NewDatabase(ethdb.NewMemDatabase()))
 		// simulate that the new head block included tx0 and tx1
 		c.statedb.SetNonce(c.address, 2)
 		c.statedb.SetBalance(c.address, new(big.Int).SetUint64(params.Ether))
@@ -175,10 +173,9 @@ func TestStateChangeDuringTransactionPoolReset(t *testing.T) {
 	t.Parallel()
 
 	var (
-		db         = ethdb.NewMemDatabase()
 		key, _     = crypto.GenerateKey()
 		address    = crypto.PubkeyToAddress(key.PublicKey)
-		statedb, _ = state.New(common.Hash{}, state.NewDatabase(db))
+		statedb, _ = state.New(common.Hash{}, state.NewDatabase(ethdb.NewMemDatabase()))
 		trigger    = false
 	)
 
@@ -332,8 +329,7 @@ func TestTransactionChainFork(t *testing.T) {
 
 	addr := crypto.PubkeyToAddress(key.PublicKey)
 	resetState := func() {
-		db := ethdb.NewMemDatabase()
-		statedb, _ := state.New(common.Hash{}, state.NewDatabase(db))
+		statedb, _ := state.New(common.Hash{}, state.NewDatabase(ethdb.NewMemDatabase()))
 		statedb.AddBalance(addr, big.NewInt(100000000000000))
 
 		pool.chain = &testBlockChain{statedb, 1000000, new(event.Feed)}
@@ -362,8 +358,7 @@ func TestTransactionDoubleNonce(t *testing.T) {
 
 	addr := crypto.PubkeyToAddress(key.PublicKey)
 	resetState := func() {
-		db := ethdb.NewMemDatabase()
-		statedb, _ := state.New(common.Hash{}, state.NewDatabase(db))
+		statedb, _ := state.New(common.Hash{}, state.NewDatabase(ethdb.NewMemDatabase()))
 		statedb.AddBalance(addr, big.NewInt(100000000000000))
 
 		pool.chain = &testBlockChain{statedb, 1000000, new(event.Feed)}
@@ -553,8 +548,7 @@ func TestTransactionPostponing(t *testing.T) {
 	t.Parallel()
 
 	// Create the pool to test the postponing with
-	db := ethdb.NewMemDatabase()
-	statedb, _ := state.New(common.Hash{}, state.NewDatabase(db))
+	statedb, _ := state.New(common.Hash{}, state.NewDatabase(ethdb.NewMemDatabase()))
 	blockchain := &testBlockChain{statedb, 1000000, new(event.Feed)}
 
 	pool := NewTxPool(testTxPoolConfig, params.TestChainConfig, blockchain)
@@ -769,8 +763,7 @@ func testTransactionQueueGlobalLimiting(t *testing.T, nolocals bool) {
 	t.Parallel()
 
 	// Create the pool to test the limit enforcement with
-	db := ethdb.NewMemDatabase()
-	statedb, _ := state.New(common.Hash{}, state.NewDatabase(db))
+	statedb, _ := state.New(common.Hash{}, state.NewDatabase(ethdb.NewMemDatabase()))
 	blockchain := &testBlockChain{statedb, 1000000, new(event.Feed)}
 
 	config := testTxPoolConfig
@@ -858,8 +851,7 @@ func testTransactionQueueTimeLimiting(t *testing.T, nolocals bool) {
 	evictionInterval = time.Second
 
 	// Create the pool to test the non-expiration enforcement
-	db := ethdb.NewMemDatabase()
-	statedb, _ := state.New(common.Hash{}, state.NewDatabase(db))
+	statedb, _ := state.New(common.Hash{}, state.NewDatabase(ethdb.NewMemDatabase()))
 	blockchain := &testBlockChain{statedb, 1000000, new(event.Feed)}
 
 	config := testTxPoolConfig
@@ -1013,8 +1005,7 @@ func TestTransactionPendingGlobalLimiting(t *testing.T) {
 	t.Parallel()
 
 	// Create the pool to test the limit enforcement with
-	db := ethdb.NewMemDatabase()
-	statedb, _ := state.New(common.Hash{}, state.NewDatabase(db))
+	statedb, _ := state.New(common.Hash{}, state.NewDatabase(ethdb.NewMemDatabase()))
 	blockchain := &testBlockChain{statedb, 1000000, new(event.Feed)}
 
 	config := testTxPoolConfig
@@ -1060,8 +1051,7 @@ func TestTransactionCapClearsFromAll(t *testing.T) {
 	t.Parallel()
 
 	// Create the pool to test the limit enforcement with
-	db := ethdb.NewMemDatabase()
-	statedb, _ := state.New(common.Hash{}, state.NewDatabase(db))
+	statedb, _ := state.New(common.Hash{}, state.NewDatabase(ethdb.NewMemDatabase()))
 	blockchain := &testBlockChain{statedb, 1000000, new(event.Feed)}
 
 	config := testTxPoolConfig
@@ -1095,8 +1085,7 @@ func TestTransactionPendingMinimumAllowance(t *testing.T) {
 	t.Parallel()
 
 	// Create the pool to test the limit enforcement with
-	db := ethdb.NewMemDatabase()
-	statedb, _ := state.New(common.Hash{}, state.NewDatabase(db))
+	statedb, _ := state.New(common.Hash{}, state.NewDatabase(ethdb.NewMemDatabase()))
 	blockchain := &testBlockChain{statedb, 1000000, new(event.Feed)}
 
 	config := testTxPoolConfig
@@ -1144,8 +1133,7 @@ func TestTransactionPoolRepricing(t *testing.T) {
 	t.Parallel()
 
 	// Create the pool to test the pricing enforcement with
-	db := ethdb.NewMemDatabase()
-	statedb, _ := state.New(common.Hash{}, state.NewDatabase(db))
+	statedb, _ := state.New(common.Hash{}, state.NewDatabase(ethdb.NewMemDatabase()))
 	blockchain := &testBlockChain{statedb, 1000000, new(event.Feed)}
 
 	pool := NewTxPool(testTxPoolConfig, params.TestChainConfig, blockchain)
@@ -1266,8 +1254,7 @@ func TestTransactionPoolRepricingKeepsLocals(t *testing.T) {
 	t.Parallel()
 
 	// Create the pool to test the pricing enforcement with
-	db := ethdb.NewMemDatabase()
-	statedb, _ := state.New(common.Hash{}, state.NewDatabase(db))
+	statedb, _ := state.New(common.Hash{}, state.NewDatabase(ethdb.NewMemDatabase()))
 	blockchain := &testBlockChain{statedb, 1000000, new(event.Feed)}
 
 	pool := NewTxPool(testTxPoolConfig, params.TestChainConfig, blockchain)
@@ -1329,8 +1316,7 @@ func TestTransactionPoolUnderpricing(t *testing.T) {
 	t.Parallel()
 
 	// Create the pool to test the pricing enforcement with
-	db := ethdb.NewMemDatabase()
-	statedb, _ := state.New(common.Hash{}, state.NewDatabase(db))
+	statedb, _ := state.New(common.Hash{}, state.NewDatabase(ethdb.NewMemDatabase()))
 	blockchain := &testBlockChain{statedb, 1000000, new(event.Feed)}
 
 	config := testTxPoolConfig
@@ -1436,8 +1422,7 @@ func TestTransactionPoolStableUnderpricing(t *testing.T) {
 	t.Parallel()
 
 	// Create the pool to test the pricing enforcement with
-	db := ethdb.NewMemDatabase()
-	statedb, _ := state.New(common.Hash{}, state.NewDatabase(db))
+	statedb, _ := state.New(common.Hash{}, state.NewDatabase(ethdb.NewMemDatabase()))
 	blockchain := &testBlockChain{statedb, 1000000, new(event.Feed)}
 
 	config := testTxPoolConfig
@@ -1503,8 +1488,7 @@ func TestTransactionReplacement(t *testing.T) {
 	t.Parallel()
 
 	// Create the pool to test the pricing enforcement with
-	db := ethdb.NewMemDatabase()
-	statedb, _ := state.New(common.Hash{}, state.NewDatabase(db))
+	statedb, _ := state.New(common.Hash{}, state.NewDatabase(ethdb.NewMemDatabase()))
 	blockchain := &testBlockChain{statedb, 1000000, new(event.Feed)}
 
 	pool := NewTxPool(testTxPoolConfig, params.TestChainConfig, blockchain)
@@ -1598,8 +1582,7 @@ func testTransactionJournaling(t *testing.T, nolocals bool) {
 	os.Remove(journal)
 
 	// Create the original pool to inject transaction into the journal
-	db := ethdb.NewMemDatabase()
-	statedb, _ := state.New(common.Hash{}, state.NewDatabase(db))
+	statedb, _ := state.New(common.Hash{}, state.NewDatabase(ethdb.NewMemDatabase()))
 	blockchain := &testBlockChain{statedb, 1000000, new(event.Feed)}
 
 	config := testTxPoolConfig
@@ -1697,8 +1680,7 @@ func TestTransactionStatusCheck(t *testing.T) {
 	t.Parallel()
 
 	// Create the pool to test the status retrievals with
-	db := ethdb.NewMemDatabase()
-	statedb, _ := state.New(common.Hash{}, state.NewDatabase(db))
+	statedb, _ := state.New(common.Hash{}, state.NewDatabase(ethdb.NewMemDatabase()))
 	blockchain := &testBlockChain{statedb, 1000000, new(event.Feed)}
 
 	pool := NewTxPool(testTxPoolConfig, params.TestChainConfig, blockchain)
diff --git a/core/vm/runtime/runtime.go b/core/vm/runtime/runtime.go
index 8de73e5ab3ef..c8c5d34d9d41 100644
--- a/core/vm/runtime/runtime.go
+++ b/core/vm/runtime/runtime.go
@@ -99,8 +99,7 @@ func Execute(code, input []byte, cfg *Config) ([]byte, *state.StateDB, error) {
 	setDefaults(cfg)
 
 	if cfg.State == nil {
-		db := ethdb.NewMemDatabase()
-		cfg.State, _ = state.New(common.Hash{}, state.NewDatabase(db))
+		cfg.State, _ = state.New(common.Hash{}, state.NewDatabase(ethdb.NewMemDatabase()))
 	}
 	var (
 		address = common.BytesToAddress([]byte("contract"))
@@ -130,8 +129,7 @@ func Create(input []byte, cfg *Config) ([]byte, common.Address, uint64, error) {
 	setDefaults(cfg)
 
 	if cfg.State == nil {
-		db := ethdb.NewMemDatabase()
-		cfg.State, _ = state.New(common.Hash{}, state.NewDatabase(db))
+		cfg.State, _ = state.New(common.Hash{}, state.NewDatabase(ethdb.NewMemDatabase()))
 	}
 	var (
 		vmenv  = NewEnv(cfg)
diff --git a/core/vm/runtime/runtime_test.go b/core/vm/runtime/runtime_test.go
index c061dc2ec541..ef664bda30cd 100644
--- a/core/vm/runtime/runtime_test.go
+++ b/core/vm/runtime/runtime_test.go
@@ -94,8 +94,7 @@ func TestExecute(t *testing.T) {
 }
 
 func TestCall(t *testing.T) {
-	db := ethdb.NewMemDatabase()
-	state, _ := state.New(common.Hash{}, state.NewDatabase(db))
+	state, _ := state.New(common.Hash{}, state.NewDatabase(ethdb.NewMemDatabase()))
 	address := common.HexToAddress("0x0a")
 	state.SetCode(address, []byte{
 		byte(vm.PUSH1), 10,
diff --git a/eth/api_test.go b/eth/api_test.go
index ed1889cd26bf..47b062a40c46 100644
--- a/eth/api_test.go
+++ b/eth/api_test.go
@@ -31,8 +31,7 @@ var dumper = spew.ConfigState{Indent: "    "}
 func TestStorageRangeAt(t *testing.T) {
 	// Create a state where account 0x010000... has a few storage entries.
 	var (
-		db       = ethdb.NewMemDatabase()
-		state, _ = state.New(common.Hash{}, state.NewDatabase(db))
+		state, _ = state.New(common.Hash{}, state.NewDatabase(ethdb.NewMemDatabase()))
 		addr     = common.Address{0x01}
 		keys     = []common.Hash{ // hashes of Keys of storage
 			common.HexToHash("340dd630ad21bf010b4e676dbfa9ba9a02175262d1fa356232cfde6cb5b47ef2"),
diff --git a/eth/tracers/tracers_test.go b/eth/tracers/tracers_test.go
index a58ef1af3380..d25fc459a1d0 100644
--- a/eth/tracers/tracers_test.go
+++ b/eth/tracers/tracers_test.go
@@ -159,8 +159,7 @@ func TestCallTracer(t *testing.T) {
 				GasLimit:    uint64(test.Context.GasLimit),
 				GasPrice:    tx.GasPrice(),
 			}
-			db := ethdb.NewMemDatabase()
-			statedb := tests.MakePreState(db, test.Genesis.Alloc)
+			statedb := tests.MakePreState(ethdb.NewMemDatabase(), test.Genesis.Alloc)
 
 			// Create the tracer, the EVM environment and run it
 			tracer, err := New("callTracer")
diff --git a/ethdb/database_test.go b/ethdb/database_test.go
index bc680ff93887..2deb50988caa 100644
--- a/ethdb/database_test.go
+++ b/ethdb/database_test.go
@@ -53,8 +53,7 @@ func TestLDB_PutGet(t *testing.T) {
 }
 
 func TestMemoryDB_PutGet(t *testing.T) {
-	db := ethdb.NewMemDatabase()
-	testPutGet(db, t)
+	testPutGet(ethdb.NewMemDatabase(), t)
 }
 
 func testPutGet(db ethdb.Database, t *testing.T) {
@@ -131,8 +130,7 @@ func TestLDB_ParallelPutGet(t *testing.T) {
 }
 
 func TestMemoryDB_ParallelPutGet(t *testing.T) {
-	db := ethdb.NewMemDatabase()
-	testParallelPutGet(db, t)
+	testParallelPutGet(ethdb.NewMemDatabase(), t)
 }
 
 func testParallelPutGet(db ethdb.Database, t *testing.T) {
diff --git a/les/handler_test.go b/les/handler_test.go
index d24b2c66599a..31aad3ed450d 100644
--- a/les/handler_test.go
+++ b/les/handler_test.go
@@ -51,8 +51,7 @@ func TestGetBlockHeadersLes1(t *testing.T) { testGetBlockHeaders(t, 1) }
 func TestGetBlockHeadersLes2(t *testing.T) { testGetBlockHeaders(t, 2) }
 
 func testGetBlockHeaders(t *testing.T, protocol int) {
-	db := ethdb.NewMemDatabase()
-	pm := newTestProtocolManagerMust(t, false, downloader.MaxHashFetch+15, nil, nil, nil, db)
+	pm := newTestProtocolManagerMust(t, false, downloader.MaxHashFetch+15, nil, nil, nil, ethdb.NewMemDatabase())
 	bc := pm.blockchain.(*core.BlockChain)
 	peer, _ := newTestPeer(t, "peer", protocol, pm, true)
 	defer peer.close()
@@ -181,8 +180,7 @@ func TestGetBlockBodiesLes1(t *testing.T) { testGetBlockBodies(t, 1) }
 func TestGetBlockBodiesLes2(t *testing.T) { testGetBlockBodies(t, 2) }
 
 func testGetBlockBodies(t *testing.T, protocol int) {
-	db := ethdb.NewMemDatabase()
-	pm := newTestProtocolManagerMust(t, false, downloader.MaxBlockFetch+15, nil, nil, nil, db)
+	pm := newTestProtocolManagerMust(t, false, downloader.MaxBlockFetch+15, nil, nil, nil, ethdb.NewMemDatabase())
 	bc := pm.blockchain.(*core.BlockChain)
 	peer, _ := newTestPeer(t, "peer", protocol, pm, true)
 	defer peer.close()
@@ -259,8 +257,7 @@ func TestGetCodeLes2(t *testing.T) { testGetCode(t, 2) }
 
 func testGetCode(t *testing.T, protocol int) {
 	// Assemble the test environment
-	db := ethdb.NewMemDatabase()
-	pm := newTestProtocolManagerMust(t, false, 4, testChainGen, nil, nil, db)
+	pm := newTestProtocolManagerMust(t, false, 4, testChainGen, nil, nil, ethdb.NewMemDatabase())
 	bc := pm.blockchain.(*core.BlockChain)
 	peer, _ := newTestPeer(t, "peer", protocol, pm, true)
 	defer peer.close()
diff --git a/tests/state_test_util.go b/tests/state_test_util.go
index ff71e0eb917a..84581fae18d9 100644
--- a/tests/state_test_util.go
+++ b/tests/state_test_util.go
@@ -126,8 +126,7 @@ func (t *StateTest) Run(subtest StateSubtest, vmconfig vm.Config) (*state.StateD
 		return nil, UnsupportedForkError{subtest.Fork}
 	}
 	block := t.genesis(config).ToBlock(nil)
-	db := ethdb.NewMemDatabase()
-	statedb := MakePreState(db, t.json.Pre)
+	statedb := MakePreState(ethdb.NewMemDatabase(), t.json.Pre)
 
 	post := t.json.Post[subtest.Fork][subtest.Index]
 	msg, err := t.json.Tx.toMessage(post)
diff --git a/tests/vm_test_util.go b/tests/vm_test_util.go
index c9cc4a59ef11..cb81c5b94e39 100644
--- a/tests/vm_test_util.go
+++ b/tests/vm_test_util.go
@@ -79,8 +79,7 @@ type vmExecMarshaling struct {
 }
 
 func (t *VMTest) Run(vmconfig vm.Config) error {
-	db := ethdb.NewMemDatabase()
-	statedb := MakePreState(db, t.json.Pre)
+	statedb := MakePreState(ethdb.NewMemDatabase(), t.json.Pre)
 	ret, gasRemaining, err := t.exec(statedb, vmconfig)
 
 	if t.json.GasRemaining == nil {
diff --git a/trie/secure_trie_test.go b/trie/secure_trie_test.go
index 85173d116fc7..d16d999684a3 100644
--- a/trie/secure_trie_test.go
+++ b/trie/secure_trie_test.go
@@ -28,18 +28,14 @@ import (
 )
 
 func newEmptySecure() *SecureTrie {
-	diskdb := ethdb.NewMemDatabase()
-	triedb := NewDatabase(diskdb)
-
-	trie, _ := NewSecure(common.Hash{}, triedb, 0)
+	trie, _ := NewSecure(common.Hash{}, NewDatabase(ethdb.NewMemDatabase()), 0)
 	return trie
 }
 
 // makeTestSecureTrie creates a large enough secure trie for testing.
 func makeTestSecureTrie() (*Database, *SecureTrie, map[string][]byte) {
 	// Create an empty trie
-	diskdb := ethdb.NewMemDatabase()
-	triedb := NewDatabase(diskdb)
+	triedb := NewDatabase(ethdb.NewMemDatabase())
 
 	trie, _ := NewSecure(common.Hash{}, triedb, 0)
 
diff --git a/trie/sync_test.go b/trie/sync_test.go
index 505d79f25bc7..142a6f5b1a5c 100644
--- a/trie/sync_test.go
+++ b/trie/sync_test.go
@@ -27,8 +27,7 @@ import (
 // makeTestTrie create a sample test trie to test node-wise reconstruction.
 func makeTestTrie() (*Database, *Trie, map[string][]byte) {
 	// Create an empty trie
-	diskdb := ethdb.NewMemDatabase()
-	triedb := NewDatabase(diskdb)
+	triedb := NewDatabase(ethdb.NewMemDatabase())
 	trie, _ := New(common.Hash{}, triedb)
 
 	// Fill it with some arbitrary data
@@ -89,18 +88,13 @@ func checkTrieConsistency(db *Database, root common.Hash) error {
 
 // Tests that an empty trie is not scheduled for syncing.
 func TestEmptyTrieSync(t *testing.T) {
-	diskdbA := ethdb.NewMemDatabase()
-	triedbA := NewDatabase(diskdbA)
-
-	diskdbB := ethdb.NewMemDatabase()
-	triedbB := NewDatabase(diskdbB)
-
-	emptyA, _ := New(common.Hash{}, triedbA)
-	emptyB, _ := New(emptyRoot, triedbB)
+	dbA := NewDatabase(ethdb.NewMemDatabase())
+	dbB := NewDatabase(ethdb.NewMemDatabase())
+	emptyA, _ := New(common.Hash{}, dbA)
+	emptyB, _ := New(emptyRoot, dbB)
 
 	for i, trie := range []*Trie{emptyA, emptyB} {
-		diskdb := ethdb.NewMemDatabase()
-		if req := NewTrieSync(trie.Hash(), diskdb, nil).Missing(1); len(req) != 0 {
+		if req := NewTrieSync(trie.Hash(), ethdb.NewMemDatabase(), nil).Missing(1); len(req) != 0 {
 			t.Errorf("test %d: content requested for empty trie: %v", i, req)
 		}
 	}
diff --git a/trie/trie_test.go b/trie/trie_test.go
index 1a4e3385b9fd..f8e5fd12a184 100644
--- a/trie/trie_test.go
+++ b/trie/trie_test.go
@@ -43,8 +43,7 @@ func init() {
 
 // Used for testing
 func newEmpty() *Trie {
-	diskdb := ethdb.NewMemDatabase()
-	trie, _ := New(common.Hash{}, NewDatabase(diskdb))
+	trie, _ := New(common.Hash{}, NewDatabase(ethdb.NewMemDatabase()))
 	return trie
 }
 
@@ -68,8 +67,7 @@ func TestNull(t *testing.T) {
 }
 
 func TestMissingRoot(t *testing.T) {
-	diskdb := ethdb.NewMemDatabase()
-	trie, err := New(common.HexToHash("0beec7b5ea3f0fdbc95d0dd47f3c5bc275da8a33"), NewDatabase(diskdb))
+	trie, err := New(common.HexToHash("0beec7b5ea3f0fdbc95d0dd47f3c5bc275da8a33"), NewDatabase(ethdb.NewMemDatabase()))
 	if trie != nil {
 		t.Error("New returned non-nil trie for invalid root")
 	}
@@ -413,8 +411,7 @@ func (randTest) Generate(r *rand.Rand, size int) reflect.Value {
 }
 
 func runRandTest(rt randTest) bool {
-	diskdb := ethdb.NewMemDatabase()
-	triedb := NewDatabase(diskdb)
+	triedb := NewDatabase(ethdb.NewMemDatabase())
 
 	tr, _ := New(common.Hash{}, triedb)
 	values := make(map[string]string) // tracks content of the trie