ledger

Documentation

Index

• type BlockAndPvtData
• type BlockPvtData
• type ChaincodeLifecycleDetails
• type ChaincodeLifecycleInfo
• type CollConfigNotDefinedError
  • func (e *CollConfigNotDefinedError) Error() string
• type CollectionConfigInfo
• type CommitOptions
• type ConfigHistoryRetriever
• type DeployedChaincodeInfo
• type DeployedChaincodeInfoProvider
• type ErrCollectionConfigNotYetAvailable
  • func (e *ErrCollectionConfigNotYetAvailable) Error() string
• type HealthCheckRegistry
• type HistoryQueryExecutor
• type Initializer
• type InvalidCollNameError
  • func (e *InvalidCollNameError) Error() string
• type MembershipInfoProvider
• type MissingBlockPvtdataInfo
• type MissingCollectionPvtDataInfo
• type MissingPvtData
• type MissingPvtDataInfo
  • func (missingPvtDataInfo MissingPvtDataInfo) Add(blkNum, txNum uint64, ns, coll string)
• type MissingPvtDataTracker
• type NotFoundInIndexErr
  • func (NotFoundInIndexErr) Error() string
• type PeerLedger
• type PeerLedgerProvider
• type PvtCollFilter
• type PvtNsCollFilter
  • func NewPvtNsCollFilter() PvtNsCollFilter
  • func (filter PvtNsCollFilter) Add(ns string, coll string)
  • func (filter PvtNsCollFilter) Has(ns string, coll string) bool
• type PvtdataHashMismatch
• type QueryExecutor
• type QueryResultsIterator
• type SimpleQueryExecutor
• type StateListener
• type StateUpdateTrigger
• type StateUpdates
• type TxMissingPvtDataMap
  • func (txMissingPvtData TxMissingPvtDataMap) Add(txNum uint64, ns, coll string, isEligible bool)
• type TxPvtData
  • func (pvtdata *TxPvtData) Has(ns string, coll string) bool
• type TxPvtDataMap
• type TxSimulationResults
  • func (txSim *TxSimulationResults) ContainsPvtWrites() bool
  • func (txSim *TxSimulationResults) GetPubSimulationBytes() ([]byte, error)
  • func (txSim *TxSimulationResults) GetPvtSimulationBytes() ([]byte, error)
• type TxSimulator

Types

type BlockAndPvtData

type BlockAndPvtData struct {
	Block          *common.Block
	PvtData        TxPvtDataMap
	MissingPvtData TxMissingPvtDataMap
}

BlockAndPvtData encapsulates the block and a map that contains the tuples <seqInBlock, *TxPvtData> The map is expected to contain the entries only for the transactions that has associated pvt data

type BlockPvtData

type BlockPvtData struct {
	BlockNum  uint64
	WriteSets TxPvtDataMap
}

BlockPvtData contains the private data for a block

type ChaincodeLifecycleDetails

type ChaincodeLifecycleDetails struct {
	Updated bool // true, if an existing chaincode is updated (false for newly deployed chaincodes).
	// Following attributes are meaningful only if 'Updated' is true
	HashChanged        bool     // true, if the chaincode code package is changed
	CollectionsUpdated []string // names of the collections that are either added or updated
	CollectionsRemoved []string // names of the collections that are removed
}

ChaincodeLifecycleDetails captures the finer details of chaincode lifecycle event

type ChaincodeLifecycleInfo

type ChaincodeLifecycleInfo struct {
	Name    string
	Deleted bool
	Details *ChaincodeLifecycleDetails // Can contain finer details about lifecycle event that can be used for certain optimization
}

ChaincodeLifecycleInfo captures the update info of a chaincode

type CollConfigNotDefinedError

type CollConfigNotDefinedError struct {
	Ns string
}

CollConfigNotDefinedError is returned whenever an operation is requested on a collection whose config has not been defined

func (*CollConfigNotDefinedError) Error

func (e *CollConfigNotDefinedError) Error() string

type CollectionConfigInfo

type CollectionConfigInfo struct {
	CollectionConfig   *common.CollectionConfigPackage
	CommittingBlockNum uint64
}

CollectionConfigInfo encapsulates a collection config for a chaincode and its committing block number

type CommitOptions

type CommitOptions struct {
	FetchPvtDataFromLedger bool
}

CommitOptions encapsulates options associated with a block commit.

type ConfigHistoryRetriever

type ConfigHistoryRetriever interface {
	CollectionConfigAt(blockNum uint64, chaincodeName string) (*CollectionConfigInfo, error)
	MostRecentCollectionConfigBelow(blockNum uint64, chaincodeName string) (*CollectionConfigInfo, error)
}

ConfigHistoryRetriever allow retrieving history of collection configs

type DeployedChaincodeInfo

type DeployedChaincodeInfo struct {
	Name                string
	Hash                []byte
	Version             string
	CollectionConfigPkg *common.CollectionConfigPackage
}

DeployedChaincodeInfo encapsulates chaincode information from the deployed chaincodes

type DeployedChaincodeInfoProvider

type DeployedChaincodeInfoProvider interface {
	Namespaces() []string
	UpdatedChaincodes(stateUpdates map[string][]*kvrwset.KVWrite) ([]*ChaincodeLifecycleInfo, error)
	ChaincodeInfo(chaincodeName string, qe SimpleQueryExecutor) (*DeployedChaincodeInfo, error)
	CollectionInfo(chaincodeName, collectionName string, qe SimpleQueryExecutor) (*common.StaticCollectionConfig, error)
}

DeployedChaincodeInfoProvider is a dependency that is used by ledger to build collection config history LSCC module is expected to provide an implementation fo this dependencys

type ErrCollectionConfigNotYetAvailable

type ErrCollectionConfigNotYetAvailable struct {
	MaxBlockNumCommitted uint64
	Msg                  string
}

ErrCollectionConfigNotYetAvailable is an error which is returned from the function ConfigHistoryRetriever.CollectionConfigAt() if the latest block number committed is lower than the block number specified in the request.

func (*ErrCollectionConfigNotYetAvailable) Error

func (e *ErrCollectionConfigNotYetAvailable) Error() string

type HealthCheckRegistry

type HealthCheckRegistry interface {
	RegisterChecker(string, healthz.HealthChecker) error
}

type HistoryQueryExecutor

type HistoryQueryExecutor interface {
	// GetHistoryForKey retrieves the history of values for a key.
	// The returned ResultsIterator contains results of type *KeyModification which is defined in protos/ledger/queryresult.
	GetHistoryForKey(namespace string, key string) (commonledger.ResultsIterator, error)
}

HistoryQueryExecutor executes the history queries

type Initializer

type Initializer struct {
	StateListeners                []StateListener
	DeployedChaincodeInfoProvider DeployedChaincodeInfoProvider
	MembershipInfoProvider        MembershipInfoProvider
	MetricsProvider               metrics.Provider
	HealthCheckRegistry           HealthCheckRegistry
}

Initializer encapsulates dependencies for PeerLedgerProvider

type InvalidCollNameError

type InvalidCollNameError struct {
	Ns, Coll string
}

InvalidCollNameError is returned whenever an operation is requested on a collection whose name is invalid

func (*InvalidCollNameError) Error

func (e *InvalidCollNameError) Error() string

type MembershipInfoProvider

type MembershipInfoProvider interface {
	// AmMemberOf checks whether the current peer is a member of the given collection
	AmMemberOf(channelName string, collectionPolicyConfig *common.CollectionPolicyConfig) (bool, error)
}

MembershipInfoProvider is a dependency that is used by ledger to determine whether the current peer is a member of a collection. Gossip module is expected to provide the dependency to ledger

type MissingBlockPvtdataInfo

type MissingBlockPvtdataInfo map[uint64][]*MissingCollectionPvtDataInfo

MissingBlockPvtdataInfo is a map of transaction number (within the block) to MissingCollectionPvtDataInfo

type MissingCollectionPvtDataInfo

type MissingCollectionPvtDataInfo struct {
	Namespace, Collection string
}

MissingCollectionPvtDataInfo includes the name of the chaincode and collection for which private data is missing

type MissingPvtData

type MissingPvtData struct {
	Namespace  string
	Collection string
	IsEligible bool
}

MissingPvtData contains a namespace and collection for which the pvtData is not present. It also denotes whether the missing pvtData is eligible (i.e., whether the peer is member of the [namespace, collection]

type MissingPvtDataInfo

type MissingPvtDataInfo map[uint64]MissingBlockPvtdataInfo

MissingPvtDataInfo is a map of block number to MissingBlockPvtdataInfo

func (MissingPvtDataInfo) Add

func (missingPvtDataInfo MissingPvtDataInfo) Add(blkNum, txNum uint64, ns, coll string)

Add adds a missing data entry to the MissingPvtDataInfo Map

type MissingPvtDataTracker

type MissingPvtDataTracker interface {
	GetMissingPvtDataInfoForMostRecentBlocks(maxBlocks int) (MissingPvtDataInfo, error)
}

MissingPvtDataTracker allows getting information about the private data that is not missing on the peer

type NotFoundInIndexErr

type NotFoundInIndexErr string

NotFoundInIndexErr is used to indicate missing entry in the index

func (NotFoundInIndexErr) Error

func (NotFoundInIndexErr) Error() string

type PeerLedger

type PeerLedger interface {
	commonledger.Ledger
	// GetTransactionByID retrieves a transaction by id
	GetTransactionByID(txID string) (*peer.ProcessedTransaction, error)
	// GetBlockByHash returns a block given it's hash
	GetBlockByHash(blockHash []byte) (*common.Block, error)
	// GetBlockByTxID returns a block which contains a transaction
	GetBlockByTxID(txID string) (*common.Block, error)
	// GetTxValidationCodeByTxID returns reason code of transaction validation
	GetTxValidationCodeByTxID(txID string) (peer.TxValidationCode, error)
	// NewTxSimulator gives handle to a transaction simulator.
	// A client can obtain more than one 'TxSimulator's for parallel execution.
	// Any snapshoting/synchronization should be performed at the implementation level if required
	NewTxSimulator(txid string) (TxSimulator, error)
	// NewQueryExecutor gives handle to a query executor.
	// A client can obtain more than one 'QueryExecutor's for parallel execution.
	// Any synchronization should be performed at the implementation level if required
	NewQueryExecutor() (QueryExecutor, error)
	// NewHistoryQueryExecutor gives handle to a history query executor.
	// A client can obtain more than one 'HistoryQueryExecutor's for parallel execution.
	// Any synchronization should be performed at the implementation level if required
	NewHistoryQueryExecutor() (HistoryQueryExecutor, error)
	// GetPvtDataAndBlockByNum returns the block and the corresponding pvt data.
	// The pvt data is filtered by the list of 'ns/collections' supplied
	// A nil filter does not filter any results and causes retrieving all the pvt data for the given blockNum
	GetPvtDataAndBlockByNum(blockNum uint64, filter PvtNsCollFilter) (*BlockAndPvtData, error)
	// GetPvtDataByNum returns only the pvt data  corresponding to the given block number
	// The pvt data is filtered by the list of 'ns/collections' supplied in the filter
	// A nil filter does not filter any results and causes retrieving all the pvt data for the given blockNum
	GetPvtDataByNum(blockNum uint64, filter PvtNsCollFilter) ([]*TxPvtData, error)
	// CommitWithPvtData commits the block and the corresponding pvt data in an atomic operation
	CommitWithPvtData(blockAndPvtdata *BlockAndPvtData, commitOpts *CommitOptions) error
	// Purge removes private read-writes set generated by endorsers at block height lesser than
	// a given maxBlockNumToRetain. In other words, Purge only retains private read-write sets
	// that were generated at block height of maxBlockNumToRetain or higher.
	PurgePrivateData(maxBlockNumToRetain uint64) error
	// PrivateDataMinBlockNum returns the lowest retained endorsement block height
	PrivateDataMinBlockNum() (uint64, error)
	//Prune prunes the blocks/transactions that satisfy the given policy
	Prune(policy commonledger.PrunePolicy) error
	// GetConfigHistoryRetriever returns the ConfigHistoryRetriever
	GetConfigHistoryRetriever() (ConfigHistoryRetriever, error)
	// CommitPvtDataOfOldBlocks commits the private data corresponding to already committed block
	// If hashes for some of the private data supplied in this function does not match
	// the corresponding hash present in the block, the unmatched private data is not
	// committed and instead the mismatch inforation is returned back
	CommitPvtDataOfOldBlocks(blockPvtData []*BlockPvtData) ([]*PvtdataHashMismatch, error)
	// GetMissingPvtDataTracker return the MissingPvtDataTracker
	GetMissingPvtDataTracker() (MissingPvtDataTracker, error)
	// DoesPvtDataInfoExist returns true when
	// (1) the ledger has pvtdata associated with the given block number (or)
	// (2) a few or all pvtdata associated with the given block number is missing but the
	//     missing info is recorded in the ledger (or)
	// (3) the block is committed and does not contain any pvtData.
	DoesPvtDataInfoExist(blockNum uint64) (bool, error)
}

PeerLedger differs from the OrdererLedger in that PeerLedger locally maintain a bitmask that tells apart valid transactions from invalid ones

type PeerLedgerProvider

type PeerLedgerProvider interface {
	Initialize(initializer *Initializer) error
	// Create creates a new ledger with the given genesis block.
	// This function guarantees that the creation of ledger and committing the genesis block would an atomic action
	// The chain id retrieved from the genesis block is treated as a ledger id
	Create(genesisBlock *common.Block) (PeerLedger, error)
	// Open opens an already created ledger
	Open(ledgerID string) (PeerLedger, error)
	// Exists tells whether the ledger with given id exists
	Exists(ledgerID string) (bool, error)
	// List lists the ids of the existing ledgers
	List() ([]string, error)
	// Close closes the PeerLedgerProvider
	Close()
}

PeerLedgerProvider provides handle to ledger instances

type PvtCollFilter

type PvtCollFilter map[string]bool

PvtCollFilter represents the set of the collection names (as keys of the map with value 'true')

type PvtNsCollFilter

type PvtNsCollFilter map[string]PvtCollFilter

PvtNsCollFilter specifies the tuple <namespace, PvtCollFilter>

func NewPvtNsCollFilter

func NewPvtNsCollFilter() PvtNsCollFilter

NewPvtNsCollFilter constructs an empty PvtNsCollFilter

func (PvtNsCollFilter) Add

func (filter PvtNsCollFilter) Add(ns string, coll string)

Add adds a namespace-collection tuple to the filter

func (PvtNsCollFilter) Has

func (filter PvtNsCollFilter) Has(ns string, coll string) bool

Has returns true if the filter has the entry for tuple namespace-collection

type PvtdataHashMismatch

type PvtdataHashMismatch struct {
	BlockNum, TxNum       uint64
	Namespace, Collection string
	ExpectedHash          []byte
}

PvtdataHashMismatch is used when the hash of private write-set does not match the corresponding hash present in the block See function `PeerLedger.CommitPvtData` for the usages

type QueryExecutor

type QueryExecutor interface {
	SimpleQueryExecutor
	// GetStateMetadata returns the metadata for given namespace and key
	GetStateMetadata(namespace, key string) (map[string][]byte, error)
	// GetStateMultipleKeys gets the values for multiple keys in a single call
	GetStateMultipleKeys(namespace string, keys []string) ([][]byte, error)
	// GetStateRangeScanIteratorWithMetadata returns an iterator that contains all the key-values between given key ranges.
	// startKey is included in the results and endKey is excluded. An empty startKey refers to the first available key
	// and an empty endKey refers to the last available key. For scanning all the keys, both the startKey and the endKey
	// can be supplied as empty strings. However, a full scan should be used judiciously for performance reasons.
	// metadata is a map of additional query parameters
	// The returned ResultsIterator contains results of type *KV which is defined in protos/ledger/queryresult.
	GetStateRangeScanIteratorWithMetadata(namespace string, startKey, endKey string, metadata map[string]interface{}) (QueryResultsIterator, error)
	// ExecuteQuery executes the given query and returns an iterator that contains results of type specific to the underlying data store.
	// Only used for state databases that support query
	// For a chaincode, the namespace corresponds to the chaincodeId
	// The returned ResultsIterator contains results of type *KV which is defined in protos/ledger/queryresult.
	ExecuteQuery(namespace, query string) (commonledger.ResultsIterator, error)
	// ExecuteQueryWithMetadata executes the given query and returns an iterator that contains results of type specific to the underlying data store.
	// metadata is a map of additional query parameters
	// Only used for state databases that support query
	// For a chaincode, the namespace corresponds to the chaincodeId
	// The returned ResultsIterator contains results of type *KV which is defined in protos/ledger/queryresult.
	ExecuteQueryWithMetadata(namespace, query string, metadata map[string]interface{}) (QueryResultsIterator, error)
	// GetPrivateData gets the value of a private data item identified by a tuple <namespace, collection, key>
	GetPrivateData(namespace, collection, key string) ([]byte, error)
	// GetPrivateDataHash gets the hash of the value of a private data item identified by a tuple <namespace, collection, key>
	// Function `GetPrivateData` is only meaningful when it is invoked on a peer that is authorized to have the private data
	// for the collection <namespace, collection>. However, the function `GetPrivateDataHash` can be invoked on any peer
	// to get the hash of the current value
	GetPrivateDataHash(namespace, collection, key string) ([]byte, error)
	// GetPrivateDataMetadata gets the metadata of a private data item identified by a tuple <namespace, collection, key>
	GetPrivateDataMetadata(namespace, collection, key string) (map[string][]byte, error)
	// GetPrivateDataMetadataByHash gets the metadata of a private data item identified by a tuple <namespace, collection, keyhash>
	GetPrivateDataMetadataByHash(namespace, collection string, keyhash []byte) (map[string][]byte, error)
	// GetPrivateDataMultipleKeys gets the values for the multiple private data items in a single call
	GetPrivateDataMultipleKeys(namespace, collection string, keys []string) ([][]byte, error)
	// GetPrivateDataRangeScanIterator returns an iterator that contains all the key-values between given key ranges.
	// startKey is included in the results and endKey is excluded. An empty startKey refers to the first available key
	// and an empty endKey refers to the last available key. For scanning all the keys, both the startKey and the endKey
	// can be supplied as empty strings. However, a full scan shuold be used judiciously for performance reasons.
	// The returned ResultsIterator contains results of type *KV which is defined in protos/ledger/queryresult.
	GetPrivateDataRangeScanIterator(namespace, collection, startKey, endKey string) (commonledger.ResultsIterator, error)
	// ExecuteQuery executes the given query and returns an iterator that contains results of type specific to the underlying data store.
	// Only used for state databases that support query
	// For a chaincode, the namespace corresponds to the chaincodeId
	// The returned ResultsIterator contains results of type *KV which is defined in protos/ledger/queryresult.
	ExecuteQueryOnPrivateData(namespace, collection, query string) (commonledger.ResultsIterator, error)
	// Done releases resources occupied by the QueryExecutor
	Done()
}

QueryExecutor executes the queries Get* methods are for supporting KV-based data model. ExecuteQuery method is for supporting a rich datamodel and query support

ExecuteQuery method in the case of a rich data model is expected to support queries on latest state, historical state and on the intersection of state and transactions

type QueryResultsIterator

type QueryResultsIterator interface {
	commonledger.ResultsIterator
	// GetBookmarkAndClose returns a paging bookmark and releases resources occupied by the iterator
	GetBookmarkAndClose() string
}

QueryResultsIterator - an iterator for query result set

type SimpleQueryExecutor

type SimpleQueryExecutor interface {
	// GetState gets the value for given namespace and key. For a chaincode, the namespace corresponds to the chaincodeId
	GetState(namespace string, key string) ([]byte, error)
	// GetStateRangeScanIterator returns an iterator that contains all the key-values between given key ranges.
	// startKey is included in the results and endKey is excluded. An empty startKey refers to the first available key
	// and an empty endKey refers to the last available key. For scanning all the keys, both the startKey and the endKey
	// can be supplied as empty strings. However, a full scan should be used judiciously for performance reasons.
	// The returned ResultsIterator contains results of type *KV which is defined in protos/ledger/queryresult.
	GetStateRangeScanIterator(namespace string, startKey string, endKey string) (commonledger.ResultsIterator, error)
}

SimpleQueryExecutor encapsulates basic functions

type StateListener

type StateListener interface {
	InterestedInNamespaces() []string
	HandleStateUpdates(trigger *StateUpdateTrigger) error
	StateCommitDone(channelID string)
}

StateListener allows a custom code for performing additional stuff upon state change for a perticular namespace against which the listener is registered. This helps to perform custom tasks other than the state updates. A ledger implemetation is expected to invoke Function `HandleStateUpdates` once per block and the `stateUpdates` parameter passed to the function captures the state changes caused by the block for the namespace. The actual data type of stateUpdates depends on the data model enabled. For instance, for KV data model, the actual type would be proto message `github.com/petermetz/fabric/protos/ledger/rwset/kvrwset.KVWrite` Function `HandleStateUpdates` is expected to be invoked before block is committed and if this function returns an error, the ledger implementation is expected to halt block commit operation and result in a panic

type StateUpdateTrigger

type StateUpdateTrigger struct {
	LedgerID                    string
	StateUpdates                StateUpdates
	CommittingBlockNum          uint64
	CommittedStateQueryExecutor SimpleQueryExecutor
	PostCommitQueryExecutor     SimpleQueryExecutor
}

StateUpdateTrigger encapsulates the information and helper tools that may be used by a StateListener

type StateUpdates

type StateUpdates map[string]interface{}

StateUpdates is the generic type to represent the state updates

type TxMissingPvtDataMap

type TxMissingPvtDataMap map[uint64][]*MissingPvtData

TxMissingPvtDataMap is a map from txNum to the list of missing pvtData

func (TxMissingPvtDataMap) Add

func (txMissingPvtData TxMissingPvtDataMap) Add(txNum uint64, ns, coll string, isEligible bool)

Add adds a given missing private data in the MissingPrivateDataList

type TxPvtData

type TxPvtData struct {
	SeqInBlock uint64
	WriteSet   *rwset.TxPvtReadWriteSet
}

TxPvtData encapsulates the transaction number and pvt write-set for a transaction

func (*TxPvtData) Has

func (pvtdata *TxPvtData) Has(ns string, coll string) bool

Has returns true if the pvtdata includes the data for collection <ns,coll>

type TxPvtDataMap

type TxPvtDataMap map[uint64]*TxPvtData

TxPvtDataMap is a map from txNum to the pvtData

type TxSimulationResults

type TxSimulationResults struct {
	PubSimulationResults *rwset.TxReadWriteSet
	PvtSimulationResults *rwset.TxPvtReadWriteSet
}

TxSimulationResults captures the details of the simulation results

func (*TxSimulationResults) ContainsPvtWrites

func (txSim *TxSimulationResults) ContainsPvtWrites() bool

ContainsPvtWrites returns true if the simulation results include the private writes

func (*TxSimulationResults) GetPubSimulationBytes

func (txSim *TxSimulationResults) GetPubSimulationBytes() ([]byte, error)

GetPubSimulationBytes returns the serialized bytes of public readwrite set

func (*TxSimulationResults) GetPvtSimulationBytes

func (txSim *TxSimulationResults) GetPvtSimulationBytes() ([]byte, error)

GetPvtSimulationBytes returns the serialized bytes of private readwrite set

type TxSimulator

type TxSimulator interface {
	QueryExecutor
	// SetState sets the given value for the given namespace and key. For a chaincode, the namespace corresponds to the chaincodeId
	SetState(namespace string, key string, value []byte) error
	// DeleteState deletes the given namespace and key
	DeleteState(namespace string, key string) error
	// SetMultipleKeys sets the values for multiple keys in a single call
	SetStateMultipleKeys(namespace string, kvs map[string][]byte) error
	// SetStateMetadata sets the metadata associated with an existing key-tuple <namespace, key>
	SetStateMetadata(namespace, key string, metadata map[string][]byte) error
	// DeleteStateMetadata deletes the metadata (if any) associated with an existing key-tuple <namespace, key>
	DeleteStateMetadata(namespace, key string) error
	// ExecuteUpdate for supporting rich data model (see comments on QueryExecutor above)
	ExecuteUpdate(query string) error
	// SetPrivateData sets the given value to a key in the private data state represented by the tuple <namespace, collection, key>
	SetPrivateData(namespace, collection, key string, value []byte) error
	// SetPrivateDataMultipleKeys sets the values for multiple keys in the private data space in a single call
	SetPrivateDataMultipleKeys(namespace, collection string, kvs map[string][]byte) error
	// DeletePrivateData deletes the given tuple <namespace, collection, key> from private data
	DeletePrivateData(namespace, collection, key string) error
	// SetPrivateDataMetadata sets the metadata associated with an existing key-tuple <namespace, collection, key>
	SetPrivateDataMetadata(namespace, collection, key string, metadata map[string][]byte) error
	// DeletePrivateDataMetadata deletes the metadata associated with an existing key-tuple <namespace, collection, key>
	DeletePrivateDataMetadata(namespace, collection, key string) error
	// GetTxSimulationResults encapsulates the results of the transaction simulation.
	// This should contain enough detail for
	// - The update in the state that would be caused if the transaction is to be committed
	// - The environment in which the transaction is executed so as to be able to decide the validity of the environment
	//   (at a later time on a different peer) during committing the transactions
	// Different ledger implementation (or configurations of a single implementation) may want to represent the above two pieces
	// of information in different way in order to support different data-models or optimize the information representations.
	// Returned type 'TxSimulationResults' contains the simulation results for both the public data and the private data.
	// The public data simulation results are expected to be used as in V1 while the private data simulation results are expected
	// to be used by the gossip to disseminate this to the other endorsers (in phase-2 of sidedb)
	GetTxSimulationResults() (*TxSimulationResults, error)
}

TxSimulator simulates a transaction on a consistent snapshot of the 'as recent state as possible' Set* methods are for supporting KV-based data model. ExecuteUpdate method is for supporting a rich datamodel and query support