db

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 Go to latest Published: Mar 19, 2020 License: MIT Imports: 52 Imported by: 32

README

DB

DB is a json-document database backed by Threads V2.

This document describes its public API, and its internal design/architecture. Internal understanding isn't necessary to use DB, but will help understand how things are wired. Creating a DB under the default configuration will automatically build everything required to work.

Currently, a DB is backed by a single Thread. In the future, this can change making the DB map different Collections to different Threads, or any other combination.

Usage

ToDo: Describe public API here.

Internal Design

In this section, there is a high-level overview of internal DB design.

Diagram

The following diagram try to express all components and their relationships and communications:

Design

The above diagram depicts the different components inside a DB. Also, it travels through their relationships caused by a transaction commit. The inverse path, caused by a new event detected in other peer log in the thread, is somewhat similar but in the other direction.

Arrows aren't always synchronous calls, but also channel notifications and other mediums in order to inverse dependency between components. Arrows are conceptual communications.

Collections

Collections are part of DB public-api. Main responsibility: store instances of a user-defined schema.

Collections are json-schemas that describe instance types of the DB. They provide the public API for creating, deleting, updating, and querying instances within this collection. They also provide read/write transactions which have serializable isolation within the DB scope.

Indexes

Collections support indexes for faster queries on schema-defined fields. When registering a new schema (and defining a Collection), a caller may supply a list of field paths to index on. This creates an Index, which can be used to speed up queries at the expense of additional storage and compute on instance creation and updates. For dbs with a small number of instances, it may not be worth the added overhead, so as always avoid optimizing your queries until you need it!

Insertion with indexes costs approximately twice as much as without (depending on the complexity and frequency of a given index), whereas updates are only slightly more costly (almost identical in most cases). Depending on the underlying data distribution, queries can be greater than an order of magnitude faster. This depends on many factors, including the size of the db (i.e., number of instances), the uniqueness of the indexed field, and the complexity of the query. For example, in our benchmark tests using a relatively simple Collection and a relatively small db size (i.e., ~5000 instances), the query speedup for a simple OR-based equality test is ~10x. See db/bench_test.go for details or to run the benchmarks yourself.

EventCodec

This is an internal component not available in the public API. Main responsibility: Transform and apply and encode/decode transaction actions.

EventCodec is an abstraction used to:

  • Transform actions made in a txn, to an array of db.Event that will be dispatcher to be reduced.
  • Encode actions made in a txn to a format.Node which will serve as the next building block for the appended Record in the local peer log.
  • The reverse of last point, when receiving external actions to allow to be dispatched.

For example, if within a collection WriteTxn(), a new instance is created and other was updated, these two action will be sent to the EventCodec to transform them in Events. These Event have a byte payload with the encoded transformation. Currently, the only implementation of EventCodec is a jsonpatcher, which transforms these actions in json-merge/patches, and store them as payloads in events.

These events are also aggregated in a returned format.Node, which is the compatible/analogous information to be used by net.Net to add in the peer own log in the thread associated with the DB. Likewise, EventCodec also do the inverse transformation. Given a format.Node, it transforms its byte payload into actions that will be reduced in the db.

The EventCodec abstraction allows an extensibility point. If instead of a json-patcher we want to encode instance changes as full instance snapshots (i.e: instead of generating the json-patch, let generate the full instance data), we could provide another implementation of the EventCodec to use in the DB.

Similarly, more advanced encodings of JSON-Document changes can be implemented as EventCodec such as JSON-Documents-Delta-CRDTs, or a hybrid json-patch with logical clocks.

Dispatcher

This is an internal component not available in the public API. Main responsibility: Source of truth regarding known db.Events for the DB. Will notify registered parties to let them know about new ones..

Every Event generated in the DB is sent to a Dispatcher when write transactions are committed. The dispatcher is responsible for broadcasting these events to all registered Reducers. A reducer is a party which is interested in knowing about DB events. Currently, the only reducer is the DB itself.

For example, if a particular instance is updated in a Collection, these corresponding actions will be encoded as Event by the EventCodec as mentioned in the last section. These Events will be dispatched to the Dispatcher, which will:

  • Store the new event in durable storage. If the txn made multiple changes, this is done transactionally.
  • Broadcast them to all registered Reducers (which currently is only DB). Reducers will apply those changes for their own interests.

The implications of this design imply that real DB state changes can only happen when the Dispatcher broadcast new db.Events. A Reducer can't distinguish between Events generated locally or externally. External events are the results of net.Net sending new events to the Dispatcher, which means that new Events where detected in other peer logs of the same Thread.

Datastore

This is an internal component not available in the public API. Main responsibility: Delivering durable persistence for data.

Datastore is the underlying persistence of Collection instances and Dispatcher raw Event information. In both cases, their interface is a datastore.TxnDatastore to have txn guarantees.

Local Event Bus

This is an internal component not available in the public API. Main responsibility: Deliver format.Node encoded information of changes done in local commited transactions. Currently, only to SingleThreadAdapter is listening to this bus.

DB Listener

This is part of the public-api. Main responsibility: Notify external actors that the DB changed its state, with details about the change: in which collection, what action (Create, Save, Delete), and wich InstanceID.

Listeners are useful for clients that want to be notified about changes in the DB. Recall that DB state can change by external events, such as receiving external changes from other peers sharing the DB.

The client can configure which kind of events wants to be notified. Can add any number of criterias; if more than one criteria is used they will be interpreted as OR conditions. A criteria contains the following information:

  • Which collection to listen changes
  • What action is done (Create, Save, Delete)
  • Which InstanceID

Any of the above three attributes can be set empty. For example, we can listen to all changes of all instances in a collection if only the first attribute is set and the other two are left empty/default.

DBThreadAdapter (SingleThreadAdapter, unique implementation)

This is an internal component not available in the public API. Main responsibility: Responsible to be the two-way communication between DB and Threads.

Every time a new local format.Node is generated in the DB due to a write transaction commit, the DBThreadAdapter will notify net.Net that a new Record should be added to the local peer log.

Similarly, when net.Net detects new Records in other peer logs, it will dispatch them to SingleThreadAdapter. Then, it will transform it into a DB Events that will be dispatched to Dispatcher and ultimately will be reduced to impact DB state.

As said initially, currently, the DB is only mapped to a single Thread. But is possible to decide a different map, where a DB might be backed by more than one thread or any other schema. This is the component that should be taking this decisions.

net.Net

This component is part of the public-api so that it can be accessed. Main responsibility: Is the DB interface with Threads layer.

net.Net is the bidirectional communication interface to the underlying Thread backing the DB. It only interacts with DBThreadAdapter

Documentation

Overview

Package db provides a DB which manage collections

Index

Constants

View Source 
const (
	// Eq is "equals"
	Eq = JSONOperation(eq)
	// Ne is "not equal to"
	Ne = JSONOperation(ne)
	// Gt is "greater than"
	Gt = JSONOperation(gt)
	// Lt is "less than"
	Lt = JSONOperation(lt)
	// Ge is "greater than or equal to"
	Ge = JSONOperation(ge)
	// Le is "less than or equal to"
	Le = JSONOperation(le)
)

Variables

View Source 
var (
	// ErrNotFound indicates that the specified instance doesn't
	// exist in the collection.
	ErrNotFound = errors.New("instance not found")
	// ErrReadonlyTx indicates that no write operations can be done since
	// the current transaction is readonly.
	ErrReadonlyTx = errors.New("read only transaction")
	// ErrInvalidSchemaInstance indicates the current operation is from an
	// instance that doesn't satisfy the collection schema.
	ErrInvalidSchemaInstance = errors.New("instance doesn't correspond to schema")
)
View Source 
var (
	ErrUniqueExists = errors.New("unique constraint violation")
	ErrNotIndexable = errors.New("value not indexable")
	ErrNoIndexFound = errors.New("no index found")
)

ErrUniqueExists is the error thrown when data is being inserted for a unique constraint value that already exists

View Source 
var (
	// ErrInvalidSortingField is returned when a query sorts a result by a
	// non-existent field in the collection schema.
	ErrInvalidSortingField = errors.New("sorting field doesn't correspond to instance type")
	// ErrInvalidSliceType is returned when a query receives a result by a
	// slice type which doesn't correspond to the collection being queried.
	ErrInvalidSliceType = errors.New("slice type doesn't correspond to collection type")
)
View Source 
var (

	// ErrInvalidCollectionType indicates the provided default type isn't compatible
	// with a Collection type.
	ErrInvalidCollectionType = errors.New("the collection type should be a non-nil pointer to a struct that has an ID property")
)

Functions

func DefaultDecode 

func DefaultDecode(data []byte, value interface{}) error

DefaultDecode is the default decoding func from badgerhold (Gob)

func DefaultEncode 

func DefaultEncode(value interface{}) ([]byte, error)

DefaultEncode is the default encoding func from badgerhold (Gob)

func NewSimpleTx 

func NewSimpleTx(ds datastore.Datastore) datastore.Txn

Types

type Action 

type Action struct {
	Collection string
	Type       ActionType
	ID         core.InstanceID
}

type ActionType 

type ActionType int
const (
	ActionCreate ActionType = iota + 1
	ActionSave
	ActionDelete
)

type Collection 

type Collection struct {
	// contains filtered or unexported fields
}

Collection contains instances of a schema, and provides operations for creating, updating, deleting, and quering them.

func (*Collection) AddIndex 

func (c *Collection) AddIndex(path string, unique bool) error

AddIndex creates a new index based on the given path string. Set unique to true if you want a unique constraint on the given path. See https://github.com/tidwall/gjson for documentation on the supported path structure. Adding an index will override any overlapping index values if they already exist. @note: This does NOT currently build the index. If items have been added prior to adding a new index, they will NOT be indexed a posteriori.

func (*Collection) BaseKey 

func (c *Collection) BaseKey() ds.Key

func (*Collection) Create 

func (c *Collection) Create(vs ...interface{}) error

Create creates instances in the collection.

func (*Collection) Delete 

func (c *Collection) Delete(ids ...core.InstanceID) error

Delete deletes instances by its IDs. It doesn't fail if the ID doesn't exist.

func (*Collection) Find 

func (c *Collection) Find(result interface{}, q *Query) error

Find executes a Query into result.

func (*Collection) FindByID 

func (c *Collection) FindByID(id core.InstanceID, v interface{}) error

FindByID finds an instance by its ID and saves it in v. If doesn't exists returns ErrNotFound.

func (*Collection) FindJSON 

func (c *Collection) FindJSON(q *JSONQuery) (ret []string, err error)

FindJSON executes a Query in in JSONMode and returns the result.

func (*Collection) Has 

func (c *Collection) Has(ids ...core.InstanceID) (exists bool, err error)

Has returns true if all IDs exist in the collection, false otherwise.

func (*Collection) Indexes 

func (c *Collection) Indexes() map[string]Index

Indexes is a map of collection properties to Indexes

func (*Collection) ReadTxn 

func (c *Collection) ReadTxn(f func(txn *Txn) error) error

ReadTxn creates an explicit readonly transaction. Any operation that tries to mutate an instance of the collection will ErrReadonlyTx. Provides serializable isolation gurantees.

func (*Collection) Save 

func (c *Collection) Save(vs ...interface{}) error

Save saves changes of instances in the collection.

func (*Collection) WriteTxn 

func (c *Collection) WriteTxn(f func(txn *Txn) error) error

WriteTxn creates an explicit write transaction. Provides serializable isolation gurantees.

type CollectionConfig 

type CollectionConfig struct {
	Name    string
	Schema  string
	Indexes []IndexConfig
}

CollectionConfig describes a new Collection.

type Comparer 

type Comparer interface {
	Compare(other interface{}) (int, error)
}

Comparer compares a type against the encoded value in the db. The result should be 0 if current==other, -1 if current < other, and +1 if current > other. If a field in a struct doesn't specify a comparer, then the default comparison is used (convert to string and compare) this interface is already handled for standard Go Types as well as more complex ones such as those in time and big an error is returned if the type cannot be compared The concrete type will always be passedin, not a pointer

type Config 

type Config struct {
	RepoPath   string
	Datastore  ds.TxnDatastore
	EventCodec core.EventCodec
	JsonMode   bool
	Debug      bool
	LowMem     bool
}

Config has configuration parameters for a db

type Criterion 

type Criterion struct {
	// contains filtered or unexported fields
}

Criterion is a partial condition that can specify comparison operator for a field.

func Where 

func Where(field string) *Criterion

Where starts to create a query condition for a field

func (*Criterion) Eq 

func (c *Criterion) Eq(value interface{}) *Query

Eq is an equality operator against a field

func (*Criterion) Fn 

func (c *Criterion) Fn(mf MatchFunc) *Query

Fn is a custom evaluation function against a field

func (*Criterion) Ge 

func (c *Criterion) Ge(value interface{}) *Query

Ge is a greater or equal operator against a field

func (*Criterion) Gt 

func (c *Criterion) Gt(value interface{}) *Query

Gt is a greater operator against a field

func (*Criterion) Le 

func (c *Criterion) Le(value interface{}) *Query

Le is a less or equal operator against a field

func (*Criterion) Lt 

func (c *Criterion) Lt(value interface{}) *Query

Lt is a less operation against a field

func (*Criterion) Ne 

func (c *Criterion) Ne(value interface{}) *Query

Ne is a not equal operator against a field

type DB 

type DB struct {
	io.Closer
	// contains filtered or unexported fields
}

DB is the aggregate-root of events and state. External/remote events are dispatched to the DB, and are internally processed to impact collection states. Likewise, local changes in collections registered produce events dispatched externally.

func NewDB 

func NewDB(ctx context.Context, network net.Net, id thread.ID, opts ...Option) (*DB, error)

NewDB creates a new DB, which will *own* ds and dispatcher for internal use. Saying it differently, ds and dispatcher shouldn't be used externally.

func NewDBFromAddr 

func NewDBFromAddr(ctx context.Context, network net.Net, addr ma.Multiaddr, key thread.Key, opts ...Option) (*DB, error)

NewDBFromAddr creates a new DB from a thread hosted by another peer at address, which will *own* ds and dispatcher for internal use. Saying it differently, ds and dispatcher shouldn't be used externally.

func (*DB) Close 

func (d *DB) Close() error

Close closes the db.

func (*DB) GetCollection 

func (d *DB) GetCollection(name string) *Collection

GetCollection returns a collection by name.

func (*DB) Listen 

func (d *DB) Listen(los ...ListenOption) (Listener, error)

Listen returns a Listener which notifies about actions applying the defined filters. The DB *won't* wait for slow receivers, so if the channel is full, the action will be dropped.

func (*DB) NewCollection 

func (d *DB) NewCollection(config CollectionConfig) (*Collection, error)

NewCollection creates a new collection in the db with a JSON schema.

func (*DB) NewCollectionFromInstance 

func (d *DB) NewCollectionFromInstance(name string, defaultInstance interface{}) (*Collection, error)

NewCollectionFromInstance creates a new collection in the db by infering type from a defaultInstance.

func (*DB) Reduce 

func (d *DB) Reduce(events []core.Event) error

Reduce processes txn events into the collections.

type Datastore 

type Datastore struct {
	kt.KeyTransform
	ds.Datastore
	// contains filtered or unexported fields
}

Datastore keeps a KeyTransform function

func (*Datastore) NewTransaction 

func (d *Datastore) NewTransaction(readOnly bool) (ds.Txn, error)

type DecodeFunc 

type DecodeFunc func(data []byte, value interface{}) error

DecodeFunc is a function for decoding a value from bytes

type EncodeFunc 

type EncodeFunc func(value interface{}) ([]byte, error)

EncodeFunc is a function for encoding a value into bytes

type Index 

type Index struct {
	IndexFunc func(name string, value []byte) (ds.Key, error)
	Unique    bool
}

Index is a function that returns the indexable, encoded bytes of the passed in bytes

type IndexConfig 

type IndexConfig struct {
	Path   string `json:"path"`
	Unique bool   `json:"unique,omitempty"`
}

IndexConfig stores the configuration for a given Index.

type Indexer 

type Indexer interface {
	BaseKey() ds.Key
	Indexes() map[string]Index //[indexname]indexFunc
}

Indexer is the interface to implement to support Collection indexes

type JSONCriterion 

type JSONCriterion struct {
	FieldPath string
	Operation JSONOperation
	Value     JSONValue
	// contains filtered or unexported fields
}

JSONCriterion represents a restriction on a field

func JSONWhere 

func JSONWhere(field string) *JSONCriterion

JSONWhere starts to create a query condition for a field

func (*JSONCriterion) Eq 

func (c *JSONCriterion) Eq(value interface{}) *JSONQuery

Eq is an equality operator against a field

func (*JSONCriterion) Ge 

func (c *JSONCriterion) Ge(value interface{}) *JSONQuery

Ge is a greater or equal operator against a field

func (*JSONCriterion) Gt 

func (c *JSONCriterion) Gt(value interface{}) *JSONQuery

Gt is a greater operator against a field

func (*JSONCriterion) Le 

func (c *JSONCriterion) Le(value interface{}) *JSONQuery

Le is a less or equal operator against a field

func (*JSONCriterion) Lt 

func (c *JSONCriterion) Lt(value interface{}) *JSONQuery

Lt is a less operation against a field

func (*JSONCriterion) Ne 

func (c *JSONCriterion) Ne(value interface{}) *JSONQuery

Ne is a not equal operator against a field

type JSONOperation 

type JSONOperation int

JSONOperation models comparison operators

type JSONQuery 

type JSONQuery struct {
	Ands  []*JSONCriterion
	Ors   []*JSONQuery
	Sort  JSONSort
	Index string
}

JSONQuery is a json-seriable query representation

func JSONOrderBy 

func JSONOrderBy(field string) *JSONQuery

JSONOrderBy specify ascending order for the query results.

func JSONOrderByDesc 

func JSONOrderByDesc(field string) *JSONQuery

JSONOrderByDesc specify descending order for the query results.

func (*JSONQuery) JSONAnd 

func (q *JSONQuery) JSONAnd(field string) *JSONCriterion

JSONAnd concatenates a new condition in an existing field.

func (*JSONQuery) JSONOr 

func (q *JSONQuery) JSONOr(orQuery *JSONQuery) *JSONQuery

JSONOr concatenates a new condition that is sufficient for an instance to satisfy, independant of the current Query. Has left-associativity as: (a And b) Or c

func (*JSONQuery) JSONOrderBy 

func (q *JSONQuery) JSONOrderBy(field string) *JSONQuery

JSONOrderBy specify ascending order for the query results. On multiple calls, only the last one is considered.

func (*JSONQuery) JSONOrderByDesc 

func (q *JSONQuery) JSONOrderByDesc(field string) *JSONQuery

JSONOrderByDesc specify descending order for the query results. On multiple calls, only the last one is considered.

func (*JSONQuery) UseIndex 

func (q *JSONQuery) UseIndex(path string) *JSONQuery

UseIndex specifies the index to use when running this query

type JSONSort 

type JSONSort struct {
	FieldPath string
	Desc      bool
}

JSONSort represents a sort order on a field

type JSONValue 

type JSONValue struct {
	String *string
	Bool   *bool
	Float  *float64
}

JSONValue models a single value in JSON

type ListenActionType 

type ListenActionType int
const (
	ListenAll ListenActionType = iota
	ListenCreate
	ListenSave
	ListenDelete
)

type ListenOption 

type ListenOption struct {
	Type       ListenActionType
	Collection string
	ID         core.InstanceID
}

type Listener 

type Listener interface {
	Channel() <-chan Action
	Close()
}

type LocalEventListener 

type LocalEventListener struct {
	// contains filtered or unexported fields
}

LocalEventListener notifies about new locally generated ipld.Nodes results of transactions

func (*LocalEventListener) Channel 

func (l *LocalEventListener) Channel() <-chan format.Node

Channel returns an unbuffered channel to receive local events

func (*LocalEventListener) Discard 

func (l *LocalEventListener) Discard()

Discard indicates that no further events will be received and ready for being garbage collected

type Manager 

type Manager struct {
	io.Closer
	// contains filtered or unexported fields
}

func NewManager 

func NewManager(network net.Net, opts ...Option) (*Manager, error)

NewManager hydrates dbs from prefixes and starts them.

func (*Manager) Close 

func (m *Manager) Close() error

Close all the in-mem dbs.

func (*Manager) GetDB 

func (m *Manager) GetDB(id thread.ID) *DB

GetDB returns a db by id from the in-mem map.

func (*Manager) Net 

func (m *Manager) Net() net.Net

Net returns the manager's thread network.

func (*Manager) NewDB 

func (m *Manager) NewDB(ctx context.Context, id thread.ID) (*DB, error)

NewDB creates a new db and prefixes its datastore with base key.

func (*Manager) NewDBFromAddr 

func (m *Manager) NewDBFromAddr(ctx context.Context, addr ma.Multiaddr, key thread.Key, collections ...CollectionConfig) (*DB, error)

NewDBFromAddr creates a new db from address and prefixes its datastore with base key. Unlike NewDB, this method takes a list of collections added to the original db that should also be added to this host.

type MarshaledResult 

type MarshaledResult struct {
	query.Result
	MarshaledValue map[string]interface{}
}

type MatchFunc 

type MatchFunc func(value interface{}) (bool, error)

MatchFunc is a function used to test an arbitrary matching value in a query

type NetBoostrapper 

type NetBoostrapper interface {
	corenet.Net
	GetIpfsLite() *ipfslite.Peer
	Bootstrap(addrs []peer.AddrInfo)
}

DefaultNetwork is a boostrapable default Net with sane defaults.

func DefaultNetwork 

func DefaultNetwork(repoPath string, opts ...NetOption) (NetBoostrapper, error)

type NetConfig 

type NetConfig struct {
	HostAddr    ma.Multiaddr
	Debug       bool
	GRPCOptions []grpc.ServerOption
}

type NetOption 

type NetOption func(c *NetConfig) error

func WithNetDebug 

func WithNetDebug(enabled bool) NetOption

func WithNetGRPCOptions 

func WithNetGRPCOptions(opts ...grpc.ServerOption) NetOption

func WithNetHostAddr 

func WithNetHostAddr(addr ma.Multiaddr) NetOption

type Option 

type Option func(*Config) error

Option takes a Config and modifies it

func WithDebug 

func WithDebug(enable bool) Option

WithDebug indicate to output debug information

func WithEventCodec 

func WithEventCodec(ec core.EventCodec) Option

WithEventCodec configure to use ec as the EventCodec manager for transforming actions in events, and viceversa

func WithJsonMode 

func WithJsonMode(enabled bool) Option

func WithLowMem 

func WithLowMem(low bool) Option

func WithRepoPath 

func WithRepoPath(path string) Option

type Query 

type Query struct {
	// contains filtered or unexported fields
}

Query allows to build queries to fetch data from a collection.

func OrderBy 

func OrderBy(field string) *Query

OrderBy specify ascending order for the query results.

func OrderByDesc 

func OrderByDesc(field string) *Query

OrderByDesc specify descending order for the query results.

func (*Query) And 

func (q *Query) And(field string) *Criterion

And concatenates a new condition in an existing field.

func (*Query) Or 

func (q *Query) Or(orQuery *Query) *Query

Or concatenates a new condition that is sufficient for an instance to satisfy, independent of the current Query. Has left-associativity as: (a And b) Or c

func (*Query) OrderBy 

func (q *Query) OrderBy(field string) *Query

OrderBy specify ascending order for the query results. On multiple calls, only the last one is considered.

func (*Query) OrderByDesc 

func (q *Query) OrderByDesc(field string) *Query

OrderByDesc specify descending order for the query results. On multiple calls, only the last one is considered.

type Reducer 

type Reducer interface {
	Reduce(events []core.Event) error
}

Reducer applies an event to an existing state.

type SimpleTx 

type SimpleTx struct {
	// contains filtered or unexported fields
}

SimpleTx implements the transaction interface for datastores who do not have any sort of underlying transactional support

func (*SimpleTx) Commit 

func (bt *SimpleTx) Commit() error

func (*SimpleTx) Delete 

func (bt *SimpleTx) Delete(key datastore.Key) error

func (*SimpleTx) Discard 

func (bt *SimpleTx) Discard()

func (*SimpleTx) Get 

func (bt *SimpleTx) Get(k datastore.Key) ([]byte, error)

func (*SimpleTx) GetSize 

func (bt *SimpleTx) GetSize(k datastore.Key) (int, error)

func (*SimpleTx) Has 

func (bt *SimpleTx) Has(k datastore.Key) (bool, error)

func (*SimpleTx) Put 

func (bt *SimpleTx) Put(key datastore.Key, val []byte) error

func (*SimpleTx) Query 

func (bt *SimpleTx) Query(q query.Query) (query.Results, error)

type TxMapDatastore 

type TxMapDatastore struct {
	*datastore.MapDatastore
	// contains filtered or unexported fields
}

func NewTxMapDatastore 

func NewTxMapDatastore() *TxMapDatastore

func (*TxMapDatastore) NewTransaction 

func (d *TxMapDatastore) NewTransaction(_ bool) (datastore.Txn, error)

type Txn 

type Txn struct {
	// contains filtered or unexported fields
}

Txn represents a read/write transaction in the db. It allows for serializable isolation level within the db.

func (*Txn) Commit 

func (t *Txn) Commit() error

Commit applies all changes done in the current transaction to the collection. This is a syncrhonous call so changes can be assumed to be applied on function return.

func (*Txn) Create 

func (t *Txn) Create(new ...interface{}) error

Create creates new instances in the collection If the ID value on the instance is nil or otherwise a null value (e.g., "" in jsonMode), the ID is updated in-place to reflect the automatically-genereted UUID.

func (*Txn) Delete 

func (t *Txn) Delete(ids ...core.InstanceID) error

Delete deletes instances by ID when the current transaction commits.

func (*Txn) Discard 

func (t *Txn) Discard()

Discard discards all changes done in the current transaction.

func (*Txn) Find 

func (t *Txn) Find(res interface{}, q *Query) error

Find executes a query and stores the result in res which should be a slice of pointers with the correct collection type. If the slice isn't empty, will be emptied.

func (*Txn) FindByID 

func (t *Txn) FindByID(id core.InstanceID, v interface{}) error

FindByID gets an instance by ID in the current txn scope.

func (*Txn) FindJSON 

func (t *Txn) FindJSON(q *JSONQuery) ([]string, error)

FindJSON queries for instances by JSONQuery

func (*Txn) Has 

func (t *Txn) Has(ids ...core.InstanceID) (bool, error)

Has returns true if all IDs exists in the collection, false otherwise.

func (*Txn) Save 

func (t *Txn) Save(updated ...interface{}) error

Save saves an instance changes to be commited when the current transaction commits.

Source Files

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