Merge pull request #4804 from multiversx/dynamic-gas-data-trie-loads

Dynamic gas data trie loads

cmd/node/config/enableEpochs.toml

@@ -272,6 +272,9 @@
     # FixDelegationChangeOwnerOnAccountEnableEpoch represents the epoch when the fix for the delegation system smart contract is enabled
     FixDelegationChangeOwnerOnAccountEnableEpoch = 3
 
+    # DynamicGasCostForDataTrieStorageLoadEnableEpoch represents the epoch when dynamic gas cost for data trie storage load will be enabled
+    DynamicGasCostForDataTrieStorageLoadEnableEpoch = 3
+
     # BLSMultiSignerEnableEpoch represents the activation epoch for different types of BLS multi-signers
     BLSMultiSignerEnableEpoch = [
         { EnableEpoch = 0, Type = "no-KOSK" },

cmd/node/config/gasSchedules/gasScheduleV1.toml

@@ -812,3 +812,16 @@
     MaxBuiltInCallsPerTx = 100
     MaxNumberOfTransfersPerTx = 250
     MaxNumberOfTrieReadsPerTx = 1500
+
+# Quadratic, Linear and Constant are the coefficients for a quadratic func. Separate variables are used for the
+# sign of each coefficient, 0 meaning positive and 1 meaning negative
+# The current values for the coefficients were computed based on benchmarking.
+# For the given coefficients, the minimum of the function must not be lower than MinimumGasCost
+[DynamicStorageLoad]
+    QuadraticCoefficient = 688
+    SignOfQuadratic = 0
+    LinearCoefficient = 31858
+    SignOfLinear = 0
+    ConstantCoefficient = 15287
+    SignOfConstant = 0
+    MinimumGasCost = 10000

cmd/node/config/gasSchedules/gasScheduleV2.toml

@@ -812,3 +812,16 @@
     MaxBuiltInCallsPerTx = 100
     MaxNumberOfTransfersPerTx = 250
     MaxNumberOfTrieReadsPerTx = 1500
+
+# Quadratic, Linear and Constant are the coefficients for a quadratic func. Separate variables are used for the
+# sign of each coefficient, 0 meaning positive and 1 meaning negative
+# The current values for the coefficients were computed based on benchmarking.
+# For the given coefficients, the minimum of the function must not be lower than MinimumGasCost
+[DynamicStorageLoad]
+    QuadraticCoefficient = 688
+    SignOfQuadratic = 0
+    LinearCoefficient = 31858
+    SignOfLinear = 0
+    ConstantCoefficient = 15287
+    SignOfConstant = 0
+    MinimumGasCost = 10000

cmd/node/config/gasSchedules/gasScheduleV3.toml

@@ -812,3 +812,16 @@
     MaxBuiltInCallsPerTx = 100
     MaxNumberOfTransfersPerTx = 250
     MaxNumberOfTrieReadsPerTx = 1500
+
+# Quadratic, Linear and Constant are the coefficients for a quadratic func. Separate variables are used for the
+# sign of each coefficient, 0 meaning positive and 1 meaning negative
+# The current values for the coefficients were computed based on benchmarking.
+# For the given coefficients, the minimum of the function must not be lower than MinimumGasCost
+[DynamicStorageLoad]
+    QuadraticCoefficient = 688
+    SignOfQuadratic = 0
+    LinearCoefficient = 31858
+    SignOfLinear = 0
+    ConstantCoefficient = 15287
+    SignOfConstant = 0
+    MinimumGasCost = 10000

cmd/node/config/gasSchedules/gasScheduleV4.toml

@@ -812,3 +812,16 @@
     MaxBuiltInCallsPerTx = 100
     MaxNumberOfTransfersPerTx = 250
     MaxNumberOfTrieReadsPerTx = 1500
+
+# Quadratic, Linear and Constant are the coefficients for a quadratic func. Separate variables are used for the
+# sign of each coefficient, 0 meaning positive and 1 meaning negative
+# The current values for the coefficients were computed based on benchmarking.
+# For the given coefficients, the minimum of the function must not be lower than MinimumGasCost
+[DynamicStorageLoad]
+    QuadraticCoefficient = 688
+    SignOfQuadratic = 0
+    LinearCoefficient = 31858
+    SignOfLinear = 0
+    ConstantCoefficient = 15287
+    SignOfConstant = 0
+    MinimumGasCost = 10000

cmd/node/config/gasSchedules/gasScheduleV5.toml

@@ -812,3 +812,16 @@
     MaxBuiltInCallsPerTx = 100
     MaxNumberOfTransfersPerTx = 250
     MaxNumberOfTrieReadsPerTx = 1500
+
+# Quadratic, Linear and Constant are the coefficients for a quadratic func. Separate variables are used for the
+# sign of each coefficient, 0 meaning positive and 1 meaning negative
+# The current values for the coefficients were computed based on benchmarking.
+# For the given coefficients, the minimum of the function must not be lower than MinimumGasCost
+[DynamicStorageLoad]
+    QuadraticCoefficient = 688
+    SignOfQuadratic = 0
+    LinearCoefficient = 31858
+    SignOfLinear = 0
+    ConstantCoefficient = 15287
+    SignOfConstant = 0
+    MinimumGasCost = 10000

cmd/node/config/gasSchedules/gasScheduleV6.toml

@@ -812,3 +812,16 @@
     MaxBuiltInCallsPerTx = 100
     MaxNumberOfTransfersPerTx = 250
     MaxNumberOfTrieReadsPerTx = 1500
+
+# Quadratic, Linear and Constant are the coefficients for a quadratic func. Separate variables are used for the
+# sign of each coefficient, 0 meaning positive and 1 meaning negative
+# The current values for the coefficients were computed based on benchmarking.
+# For the given coefficients, the minimum of the function must not be lower than MinimumGasCost
+[DynamicStorageLoad]
+    QuadraticCoefficient = 688
+    SignOfQuadratic = 0
+    LinearCoefficient = 31858
+    SignOfLinear = 0
+    ConstantCoefficient = 15287
+    SignOfConstant = 0
+    MinimumGasCost = 10000

cmd/node/config/gasSchedules/gasScheduleV7.toml

@@ -813,3 +813,16 @@
     MaxBuiltInCallsPerTx = 100
     MaxNumberOfTransfersPerTx = 250
     MaxNumberOfTrieReadsPerTx = 1500
+
+# Quadratic, Linear and Constant are the coefficients for a quadratic func. Separate variables are used for the
+# sign of each coefficient, 0 meaning positive and 1 meaning negative
+# The current values for the coefficients were computed based on benchmarking.
+# For the given coefficients, the minimum of the function must not be lower than MinimumGasCost
+[DynamicStorageLoad]
+    QuadraticCoefficient = 688
+    SignOfQuadratic = 0
+    LinearCoefficient = 31858
+    SignOfLinear = 0
+    ConstantCoefficient = 15287
+    SignOfConstant = 0
+    MinimumGasCost = 10000

common/enablers/enableEpochsHandler.go

@@ -128,6 +128,7 @@ func (handler *enableEpochsHandler) EpochConfirmed(epoch uint32, _ uint64) {
 	handler.setFlagValue(epoch >= handler.enableEpochsConfig.AutoBalanceDataTriesEnableEpoch, handler.autoBalanceDataTriesFlag, "autoBalanceDataTriesFlag", epoch, handler.enableEpochsConfig.AutoBalanceDataTriesEnableEpoch)
 	handler.setFlagValue(epoch >= handler.enableEpochsConfig.FixDelegationChangeOwnerOnAccountEnableEpoch, handler.fixDelegationChangeOwnerOnAccountFlag, "fixDelegationChangeOwnerOnAccountFlag", epoch, handler.enableEpochsConfig.FixDelegationChangeOwnerOnAccountEnableEpoch)
 	handler.setFlagValue(epoch >= handler.enableEpochsConfig.SCProcessorV2EnableEpoch, handler.scProcessorV2Flag, "scProcessorV2Flag", epoch, handler.enableEpochsConfig.SCProcessorV2EnableEpoch)
+	handler.setFlagValue(epoch >= handler.enableEpochsConfig.DynamicGasCostForDataTrieStorageLoadEnableEpoch, handler.dynamicGasCostForDataTrieStorageLoadFlag, "dynamicGasCostForDataTrieStorageLoadFlag", epoch, handler.enableEpochsConfig.DynamicGasCostForDataTrieStorageLoadEnableEpoch)
 }
 
 func (handler *enableEpochsHandler) setFlagValue(value bool, flag *atomic.Flag, flagName string, epoch uint32, flagEpoch uint32) {

common/enablers/epochFlags.go

@@ -100,6 +100,7 @@ type epochFlagsHolder struct {
 	consistentTokensValuesCheckFlag             *atomic.Flag
 	autoBalanceDataTriesFlag                    *atomic.Flag
 	fixDelegationChangeOwnerOnAccountFlag       *atomic.Flag
+	dynamicGasCostForDataTrieStorageLoadFlag    *atomic.Flag
 }
 
 func newEpochFlagsHolder() *epochFlagsHolder {
@@ -199,6 +200,7 @@ func newEpochFlagsHolder() *epochFlagsHolder {
 		changeUsernameFlag:                          &atomic.Flag{},
 		autoBalanceDataTriesFlag:                    &atomic.Flag{},
 		fixDelegationChangeOwnerOnAccountFlag:       &atomic.Flag{},
+		dynamicGasCostForDataTrieStorageLoadFlag:    &atomic.Flag{},
 	}
 }
 
@@ -729,3 +731,8 @@ func (holder *epochFlagsHolder) IsAutoBalanceDataTriesEnabled() bool {
 func (holder *epochFlagsHolder) FixDelegationChangeOwnerOnAccountEnabled() bool {
 	return holder.fixDelegationChangeOwnerOnAccountFlag.IsSet()
 }
+
+// IsDynamicGasCostForDataTrieStorageLoadEnabled returns true if dynamicGasCostForDataTrieStorageLoadFlag is enabled
+func (holder *epochFlagsHolder) IsDynamicGasCostForDataTrieStorageLoadEnabled() bool {
+	return holder.dynamicGasCostForDataTrieStorageLoadFlag.IsSet()
+}

common/interface.go

@@ -392,6 +392,7 @@ type EnableEpochsHandler interface {
 	IsChangeUsernameEnabled() bool
 	IsConsistentTokensValuesLengthCheckEnabled() bool
 	IsAutoBalanceDataTriesEnabled() bool
+	IsDynamicGasCostForDataTrieStorageLoadEnabled() bool
 	FixDelegationChangeOwnerOnAccountEnabled() bool
 
 	IsInterfaceNil() bool

config/epochConfig.go

@@ -103,6 +103,7 @@ type EnableEpochs struct {
 	AutoBalanceDataTriesEnableEpoch                   uint32
 	ConsistentTokensValuesLengthCheckEnableEpoch      uint32
 	FixDelegationChangeOwnerOnAccountEnableEpoch      uint32
+	DynamicGasCostForDataTrieStorageLoadEnableEpoch   uint32
 	BLSMultiSignerEnableEpoch                         []MultiSignerConfig
 }
 

config/tomlConfig_test.go

@@ -811,6 +811,9 @@ func TestEnableEpochConfig(t *testing.T) {
     # DeterministicSortOnValidatorsInfoEnableEpoch represents the epoch when the deterministic sorting on validators info is enabled
     DeterministicSortOnValidatorsInfoEnableEpoch = 66
 
+    # DynamicGasCostForDataTrieStorageLoadEnableEpoch represents the epoch when dynamic gas cost for data trie storage load will be enabled
+    DynamicGasCostForDataTrieStorageLoadEnableEpoch = 64
+
     # MaxNodesChangeEnableEpoch holds configuration for changing the maximum number of nodes and the enabling epoch
     MaxNodesChangeEnableEpoch = [
         { EpochEnable = 44, MaxNumNodes = 2169, NodesToShufflePerShard = 80 },
@@ -848,51 +851,53 @@ func TestEnableEpochConfig(t *testing.T) {
 			ReturnDataToLastTransferEnableEpoch:               15,
 			SenderInOutTransferEnableEpoch:                    16,
 			StakeEnableEpoch:                                  17,
-			StakingV2EnableEpoch:                              18,
-			DoubleKeyProtectionEnableEpoch:                    19,
-			ESDTEnableEpoch:                                   20,
-			GovernanceEnableEpoch:                             21,
-			DelegationManagerEnableEpoch:                      22,
-			DelegationSmartContractEnableEpoch:                23,
-			CorrectLastUnjailedEnableEpoch:                    24,
-			RelayedTransactionsV2EnableEpoch:                  25,
-			UnbondTokensV2EnableEpoch:                         26,
-			SaveJailedAlwaysEnableEpoch:                       27,
-			ReDelegateBelowMinCheckEnableEpoch:                28,
-			ValidatorToDelegationEnableEpoch:                  29,
-			WaitingListFixEnableEpoch:                         30,
-			IncrementSCRNonceInMultiTransferEnableEpoch:       31,
-			ESDTMultiTransferEnableEpoch:                      32,
-			GlobalMintBurnDisableEpoch:                        33,
-			ESDTTransferRoleEnableEpoch:                       34,
-			BuiltInFunctionOnMetaEnableEpoch:                  35,
-			ComputeRewardCheckpointEnableEpoch:                36,
-			SCRSizeInvariantCheckEnableEpoch:                  37,
-			BackwardCompSaveKeyValueEnableEpoch:               38,
-			ESDTNFTCreateOnMultiShardEnableEpoch:              39,
-			MetaESDTSetEnableEpoch:                            40,
-			AddTokensToDelegationEnableEpoch:                  41,
-			MultiESDTTransferFixOnCallBackOnEnableEpoch:       42,
-			OptimizeGasUsedInCrossMiniBlocksEnableEpoch:       43,
-			CorrectFirstQueuedEpoch:                           44,
-			DeleteDelegatorAfterClaimRewardsEnableEpoch:       45,
-			FixOOGReturnCodeEnableEpoch:                       46,
-			RemoveNonUpdatedStorageEnableEpoch:                47,
-			OptimizeNFTStoreEnableEpoch:                       48,
-			CreateNFTThroughExecByCallerEnableEpoch:            49,
-			StopDecreasingValidatorRatingWhenStuckEnableEpoch: 50,
-			FrontRunningProtectionEnableEpoch:                 51,
-			IsPayableBySCEnableEpoch:                          52,
-			CleanUpInformativeSCRsEnableEpoch:                 53,
-			StorageAPICostOptimizationEnableEpoch:             54,
-			TransformToMultiShardCreateEnableEpoch:            55,
+			StakingV2EnableEpoch:                            18,
+
+			DoubleKeyProtectionEnableEpoch:                  19,
+			ESDTEnableEpoch:                                 20,
+			GovernanceEnableEpoch:                           21,
+			DelegationManagerEnableEpoch:                    22,
+			DelegationSmartContractEnableEpoch:              23,
+			CorrectLastUnjailedEnableEpoch:                  24,
+
+			RelayedTransactionsV2EnableEpoch:                25,
+			UnbondTokensV2EnableEpoch:                       26,
+			SaveJailedAlwaysEnableEpoch:                     27,
+			ReDelegateBelowMinCheckEnableEpoch:                28,ValidatorToDelegationEnableEpoch:                29,
+
+			WaitingListFixEnableEpoch:                       30,
+			IncrementSCRNonceInMultiTransferEnableEpoch:     31,
+			ESDTMultiTransferEnableEpoch:                    32,
+			GlobalMintBurnDisableEpoch:                      33,
+			ESDTTransferRoleEnableEpoch:                     34,
+			BuiltInFunctionOnMetaEnableEpoch:                35,
+			ComputeRewardCheckpointEnableEpoch:              36,
+			SCRSizeInvariantCheckEnableEpoch:                37,
+			BackwardCompSaveKeyValueEnableEpoch:             38,
+			ESDTNFTCreateOnMultiShardEnableEpoch:            39,
+			MetaESDTSetEnableEpoch:                          40,
+			AddTokensToDelegationEnableEpoch:                41,
+			MultiESDTTransferFixOnCallBackOnEnableEpoch:     42,
+			OptimizeGasUsedInCrossMiniBlocksEnableEpoch:     43,
+			CorrectFirstQueuedEpoch:                     44,
+			DeleteDelegatorAfterClaimRewardsEnableEpoch:              45,
+			FixOOGReturnCodeEnableEpoch:                     46,
+			RemoveNonUpdatedStorageEnableEpoch:         47,
+			OptimizeNFTStoreEnableEpoch:                        48,
+			CreateNFTThroughExecByCallerEnableEpoch:               49,
+			StopDecreasingValidatorRatingWhenStuckEnableEpoch:           50,
+			FrontRunningProtectionEnableEpoch:          51,
+			IsPayableBySCEnableEpoch:           52,
+			CleanUpInformativeSCRsEnableEpoch:         53,
+			StorageAPICostOptimizationEnableEpoch:                    54,
+			TransformToMultiShardCreateEnableEpoch:        55,
 			ESDTRegisterAndSetAllRolesEnableEpoch:             56,
-			ScheduledMiniBlocksEnableEpoch:                    57,
-			CorrectJailedNotUnstakedEmptyQueueEpoch:           58,
-			DoNotReturnOldBlockInBlockchainHookEnableEpoch:    59,
-			AddFailedRelayedTxToInvalidMBsDisableEpoch:        60,
-			SCRSizeInvariantOnBuiltInResultEnableEpoch:        61,
-			CheckCorrectTokenIDForTransferRoleEnableEpoch:     62,
+			ScheduledMiniBlocksEnableEpoch:                 57,
+			CorrectJailedNotUnstakedEmptyQueueEpoch:         58,
+			DoNotReturnOldBlockInBlockchainHookEnableEpoch:            59,
+			AddFailedRelayedTxToInvalidMBsDisableEpoch:       60,
+			SCRSizeInvariantOnBuiltInResultEnableEpoch:              61,
+			CheckCorrectTokenIDForTransferRoleEnableEpoch:                   62,
 			DisableExecByCallerEnableEpoch:                    63,
 			RefactorContextEnableEpoch:                        64,
 			FailExecutionOnEveryAPIErrorEnableEpoch:           65,
@@ -902,8 +907,7 @@ func TestEnableEpochConfig(t *testing.T) {
 			ESDTMetadataContinuousCleanupEnableEpoch:          69,
 			MiniBlockPartialExecutionEnableEpoch:              70,
 			FixAsyncCallBackArgsListEnableEpoch:               71,
-			FixOldTokenLiquidityEnableEpoch:                   72,
-			RuntimeMemStoreLimitEnableEpoch:                   73,
+			FixOldTokenLiquidityEnableEpoch:                   72,RuntimeMemStoreLimitEnableEpoch:                 73,
 			SetSenderInEeiOutputTransferEnableEpoch:           74,
 			RefactorPeersMiniBlocksEnableEpoch:                75,
 			MaxBlockchainHookCountersEnableEpoch:              76,
@@ -931,6 +935,7 @@ func TestEnableEpochConfig(t *testing.T) {
 				},
 			},
 			DeterministicSortOnValidatorsInfoEnableEpoch: 66,
+			DynamicGasCostForDataTrieStorageLoadEnableEpoch: 64,
 			BLSMultiSignerEnableEpoch: []MultiSignerConfig{
 				{
 					EnableEpoch: 0,

go.mod

@@ -20,8 +20,8 @@ require (
 	github.com/multiversx/mx-chain-logger-go v1.0.13
 	github.com/multiversx/mx-chain-scenario-go v1.2.1
 	github.com/multiversx/mx-chain-storage-go v1.0.12
-	github.com/multiversx/mx-chain-vm-common-go v1.5.2
-	github.com/multiversx/mx-chain-vm-go v1.5.5
+	github.com/multiversx/mx-chain-vm-common-go v1.5.3
+	github.com/multiversx/mx-chain-vm-go v1.5.6
 	github.com/multiversx/mx-chain-vm-v1_2-go v1.2.60
 	github.com/multiversx/mx-chain-vm-v1_3-go v1.3.61
 	github.com/multiversx/mx-chain-vm-v1_4-go v1.4.87

go.sum

@@ -390,10 +390,10 @@ github.com/multiversx/mx-chain-scenario-go v1.2.1 h1:9eC6VcOEAKRRKZ7EbSWPLzCdNIM
 github.com/multiversx/mx-chain-scenario-go v1.2.1/go.mod h1:EuZY7DpNFHVNSxJR8dKE1z2I8gBYfEFFPSwNUOXptqE=
 github.com/multiversx/mx-chain-storage-go v1.0.12 h1:FrkgHPV38BO8cwdK0GUYHxVkUyOhyBBIhPz0P1e72NA=
 github.com/multiversx/mx-chain-storage-go v1.0.12/go.mod h1:/8VrMbO9CbIi0Ym3F1QPY6EENGcUq5DpEBPDt4evn9Q=
-github.com/multiversx/mx-chain-vm-common-go v1.5.2 h1:iRWJNlogjkq9w+pJZIfkVkXQFmMoRxZr6pzCfg2/K68=
-github.com/multiversx/mx-chain-vm-common-go v1.5.2/go.mod h1:sqkKMCnwkWl8DURdb9q7pctK8IANghdHY1KJLE0ox2c=
-github.com/multiversx/mx-chain-vm-go v1.5.5 h1:/ROeFnd44/vRGtnzlfUJZMBX/g3bNwxPpLTXo52XLbY=
-github.com/multiversx/mx-chain-vm-go v1.5.5/go.mod h1:5d5GC+Ibz8X27+W8TYqbsMXh8n4F/kHUbdr0bVz8o8Y=
+github.com/multiversx/mx-chain-vm-common-go v1.5.3 h1:u4ttQc+1bj92SoGeRk3EYc8JvOMDPIGyrQuQGM+YYpU=
+github.com/multiversx/mx-chain-vm-common-go v1.5.3/go.mod h1:sqkKMCnwkWl8DURdb9q7pctK8IANghdHY1KJLE0ox2c=
+github.com/multiversx/mx-chain-vm-go v1.5.6 h1:IOwq/L4dBDBjXTIAR9hHCS/D4fn2xMkkINimHWsYiUQ=
+github.com/multiversx/mx-chain-vm-go v1.5.6/go.mod h1:WCYCljlHi2UQWHQAlSw1LzDsiMlckoMzvHL2fA5VKU4=
 github.com/multiversx/mx-chain-vm-v1_2-go v1.2.60 h1:YYElal1woAT3gwcVGe2JUEqBlzMXt963BSdQHuJpTMk=
 github.com/multiversx/mx-chain-vm-v1_2-go v1.2.60/go.mod h1:3X3V/nj4G2ziTIijSEiucGn3r3S8v3CRIg5/szOtCLY=
 github.com/multiversx/mx-chain-vm-v1_3-go v1.3.61 h1:z1LkUlVNwc6mfWqFu+VTpPorDd0/Pj7/SMNXmNDdkK4=

integrationTests/benchmarks/loadFromTrie_test.go

@@ -1,17 +1,15 @@
 package benchmarks
 
 import (
-	"encoding/hex"
 	"fmt"
-	"math/rand"
-	"strings"
 	"testing"
 	"time"
 
 	"github.com/multiversx/mx-chain-core-go/hashing"
 	"github.com/multiversx/mx-chain-core-go/hashing/blake2b"
 	"github.com/multiversx/mx-chain-core-go/marshal"
 	"github.com/multiversx/mx-chain-go/common"
+	"github.com/multiversx/mx-chain-go/integrationTests"
 	"github.com/multiversx/mx-chain-go/storage"
 	"github.com/multiversx/mx-chain-go/storage/database"
 	"github.com/multiversx/mx-chain-go/storage/storageunit"
@@ -22,12 +20,6 @@ import (
 	"github.com/stretchr/testify/require"
 )
 
-var charsPool = []string{"0", "1", "2", "3", "4", "5", "6", "7", "8", "9", "A", "B", "C", "D", "E"}
-
-const (
-	keyLength = 32
-)
-
 func TestTrieLoadTime(t *testing.T) {
 	t.Skip()
 
@@ -133,33 +125,13 @@ func insertKeysIntoTrie(t *testing.T, tr common.Trie, numTrieLevels int, numChil
 }
 
 func insertInTrie(tr common.Trie, numTrieLevels int, numChildrenPerBranch int) []byte {
-	var key []byte
-	hexKeyLength := keyLength * 2
-	if numTrieLevels == 1 {
-		hexKey := generateRandHexString(hexKeyLength)
-		key, _ = hex.DecodeString(hexKey)
+	keys := integrationTests.GenerateTrieKeysForMaxLevel(numTrieLevels, numChildrenPerBranch)
+	for _, key := range keys {
 		_ = tr.Update(key, key)
-		return key
-	}
-
-	for i := 0; i < numTrieLevels-1; i++ {
-		for j := 0; j < numChildrenPerBranch-1; j++ {
-			hexKey := generateRandHexString(hexKeyLength-numTrieLevels) + strings.Repeat(charsPool[j], numTrieLevels-i) + strings.Repeat("F", i)
-			key, _ = hex.DecodeString(hexKey)
-			_ = tr.Update(key, key)
-		}
-	}
-
-	return key
-}
-
-func generateRandHexString(size int) string {
-	buff := make([]string, size)
-	for i := 0; i < size; i++ {
-		buff[i] = charsPool[rand.Intn(len(charsPool))]
 	}
 
-	return strings.Join(buff, "")
+	lastKeyIndex := len(keys) - 1
+	return keys[lastKeyIndex]
 }
 
 func getTrieStorageManager(store storage.Storer, marshaller marshal.Marshalizer, hasher hashing.Hasher) common.StorageManager {