golang源码分析：cayley(7)

2023-08-09 15:07:45 浏览数 (2)

接着我们看下writer的实现，writer的核心源码位于writer/single.go，writer的注册方式和存储的注册类似，它注册了一个single的writer

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func init() {
  graph.RegisterWriter("single", NewSingleReplication)
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type Single struct {
  qs         graph.QuadStore
  ignoreOpts graph.IgnoreOpts
}
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func NewSingle(qs graph.QuadStore, opts graph.IgnoreOpts) (graph.QuadWriter, error) {
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func NewSingleReplication(qs graph.QuadStore, opts graph.Options) (graph.QuadWriter, error) {

得到writer后就可以往里面添加四元祖，它内部是调用了quad的

ApplyDeltas

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  func (s *Single) AddQuad(q quad.Quad) error {
      return s.qs.ApplyDeltas(deltas, s.ignoreOpts)
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func (s *Single) AddQuadSet(set []quad.Quad) error {
      tx := graph.NewTransactionN(len(set))
      return s.qs.ApplyDeltas(tx.Deltas, s.ignoreOpts)

删除过程类似

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func (s *Single) RemoveQuad(q quad.Quad) error {
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func (s *Single) RemoveNode(v quad.Value) error {
        for _, d := range []quad.Direction{quad.Subject, quad.Predicate, quad.Object, quad.Label} {
    r := graph.NewResultReader(s.qs, s.qs.QuadIterator(d, gv))
    n, err := quad.Copy(del, r)
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func (s *Single) ApplyTransaction(t *graph.Transaction) error {
  return s.qs.ApplyDeltas(t.Deltas, s.ignoreOpts)

graph/quadwriter.go主要包含了插入和删除两个操作

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type Procedure int8
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const (
  Add    Procedure =  1
  Delete Procedure = -1
)

一个增量操作包含四元祖和具体动作两个部分

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type Delta struct {
  Quad   quad.Quad
  Action Procedure
}
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func Unwrap(qs QuadStore) QuadStore {

我们创建一个图数据库*Handle的时候，就是初始化了QuadStore和Writer两个属性

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type Handle struct {
  QuadStore
  QuadWriter
}
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type IgnoreOpts struct {
  IgnoreDup, IgnoreMissing bool
}

writer约定了一个接口，具体如下：

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type QuadWriter interface {
  // AddQuad adds a quad to the store.
  AddQuad(quad.Quad) error


  // TODO(barakmich): Deprecate in favor of transaction.
  // AddQuadSet adds a set of quads to the store, atomically if possible.
  AddQuadSet([]quad.Quad) error


  // RemoveQuad removes a quad matching the given one  from the database,
  // if it exists. Does nothing otherwise.
  RemoveQuad(quad.Quad) error


  // ApplyTransaction applies a set of quad changes.
  ApplyTransaction(*Transaction) error


  // RemoveNode removes all quads which have the given node as subject, predicate, object, or label.
  //
  // It returns ErrNodeNotExists if node is missing.
  RemoveNode(quad.Value) error


  // Close cleans up replication and closes the writing aspect of the database.
  Close() error
}
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type NewQuadWriterFunc func(QuadStore, Options) (QuadWriter, error)
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var writerRegistry = make(map[string]NewQuadWriterFunc)

注册函数定义如下：

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func RegisterWriter(name string, newFunc NewQuadWriterFunc) {
  if _, found := writerRegistry[name]; found {
    panic("already registered QuadWriter "   name)
  }
  writerRegistry[name] = newFunc
}
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func NewQuadWriter(name string, qs QuadStore, opts Options) (QuadWriter, error) {
  newFunc, hasNew := writerRegistry[name]
  if !hasNew {
    return nil, errors.New("replication: name '"   name   "' is not registered")
  }
  return newFunc(qs, opts)
}
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func WriterMethods() []string {
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type BatchWriter interface {
  quad.WriteCloser
  Flush() error
}
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func NewWriter(qs QuadWriter) BatchWriter {
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type batchWriter struct {
  qs  QuadWriter
  buf []quad.Quad
}
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func (w *batchWriter) flushBuffer(force bool) error {
func (w *batchWriter) WriteQuad(q quad.Quad) error {
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func NewTxWriter(tx *Transaction, p Procedure) quad.Writer {
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type txWriter struct {
  tx *Transaction
  p  Procedure
}
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func NewRemover(qs QuadWriter) BatchWriter {
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type removeWriter struct {
  qs QuadWriter
}
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func (w *removeWriter) WriteQuad(q quad.Quad) error {
  return w.qs.RemoveQuad(q)
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func NewQuadStoreReader(qs QuadStore) quad.ReadSkipCloser {
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func NewResultReader(qs QuadStore, it Iterator) quad.ReadSkipCloser {

和Writer对应，Reader包含了QuadStore和迭代器

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type quadReader struct {
  qs QuadStore
  it Iterator
}
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func (r *quadReader) ReadQuad() (quad.Quad, error) {
  if r.it.Next(context.TODO()) {
    return r.qs.Quad(r.it.Result()), nil

imports.go

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var (
  StartMorphism = path.StartMorphism
  StartPath     = path.StartPath


  NewTransaction = graph.NewTransaction
)

笔记哦核心的几个变量类型

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type Iterator = graph.Iterator
type QuadStore = graph.QuadStore
type QuadWriter = graph.QuadWriter
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type Path = path.Path
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type Handle struct {
  graph.QuadStore
  graph.QuadWriter
}

三元祖其实就是四元祖去掉label

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func Triple(subject, predicate, object interface{}) quad.Quad {
  return Quad(subject, predicate, object, nil)
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func Quad(subject, predicate, object, label interface{}) quad.Quad {
  return quad.Make(subject, predicate, object, label)

初始化图数据库的时候，指定的writer就single

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func NewGraph(name, dbpath string, opts graph.Options) (*Handle, error) {
      qs, err := graph.NewQuadStore(name, dbpath, opts)
      qw, err := graph.NewQuadWriter("single", qs, nil)
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func NewMemoryGraph() (*Handle, error) {
  return NewGraph("memstore", "", nil)

server/http/common.go里面提供了基于http服务的操作

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func jsonResponse(w http.ResponseWriter, code int, err interface{}) {
        data, _ := json.Marshal(s)
  w.Write(data)
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func HandleForRequest(h *graph.Handle, wtyp string, wopt graph.Options, r *http.Request) (*graph.Handle, error) {
      qs, err := g.ForRequest(r)
      qw, err := graph.NewQuadWriter(wtyp, qs, wopt)
      return &graph.Handle{QuadStore: qs, QuadWriter: qw}, nil

appengine/appengine.go

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func open(cfg *Config) (*graph.Handle, error) {
      qs, err := graph.NewQuadStore(cfg.DatabaseType, cfg.DatabasePath, cfg.DatabaseOptions)
      qw, err := graph.NewQuadWriter(cfg.ReplicationType, qs, cfg.ReplicationOptions)
      return &graph.Handle{QuadStore: qs, QuadWriter: qw}, nil

graph/registry.go

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func NewQuadStore(name string, dbpath string, opts Options) (QuadStore, error) {
      r, registered := storeRegistry[name]
      return r.NewFunc(dbpath, opts)
error func graph 图数据库 源码分析

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