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datastore.go
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datastore.go
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// Copyright 2014 Google Inc. All Rights Reserved.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
// Package datastore contains a Google Cloud Datastore client.
//
// This package is experimental and may make backwards-incompatible changes.
package datastore // import "google.golang.org/cloud/datastore"
import (
"errors"
"fmt"
"reflect"
"github.com/golang/protobuf/proto"
"golang.org/x/net/context"
"google.golang.org/cloud"
pb "google.golang.org/cloud/internal/datastore"
"google.golang.org/cloud/internal/transport"
)
const prodAddr = "https://www.googleapis.com/datastore/v1beta2/datasets/"
const userAgent = "gcloud-golang-datastore/20150727"
const (
// ScopeDatastore grants permissions to view and/or manage datastore entities
ScopeDatastore = "https://www.googleapis.com/auth/datastore"
// ScopeUserEmail grants permission to view the user's email address.
// It is required to access the datastore.
ScopeUserEmail = "https://www.googleapis.com/auth/userinfo.email"
)
// protoClient is an interface for *transport.ProtoClient to support injecting
// fake clients in tests.
type protoClient interface {
Call(context.Context, string, proto.Message, proto.Message) error
}
// Client is a client for reading and writing data in a datastore dataset.
type Client struct {
client protoClient
endpoint string
dataset string // Called dataset by the datastore API, synonym for project ID.
}
// NewClient creates a new Client for a given dataset.
func NewClient(ctx context.Context, projectID string, opts ...cloud.ClientOption) (*Client, error) {
o := []cloud.ClientOption{
cloud.WithEndpoint(prodAddr),
cloud.WithScopes(ScopeDatastore, ScopeUserEmail),
cloud.WithUserAgent(userAgent),
}
o = append(o, opts...)
client, err := transport.NewProtoClient(ctx, o...)
if err != nil {
return nil, fmt.Errorf("dialing: %v", err)
}
return &Client{
client: client,
dataset: projectID,
}, nil
}
var (
// ErrInvalidEntityType is returned when functions like Get or Next are
// passed a dst or src argument of invalid type.
ErrInvalidEntityType = errors.New("datastore: invalid entity type")
// ErrInvalidKey is returned when an invalid key is presented.
ErrInvalidKey = errors.New("datastore: invalid key")
// ErrNoSuchEntity is returned when no entity was found for a given key.
ErrNoSuchEntity = errors.New("datastore: no such entity")
)
type multiArgType int
const (
multiArgTypeInvalid multiArgType = iota
multiArgTypePropertyLoadSaver
multiArgTypeStruct
multiArgTypeStructPtr
multiArgTypeInterface
)
// nsKey is the type of the context.Context key to store the datastore
// namespace.
type nsKey struct{}
// WithNamespace returns a new context that limits the scope its parent
// context with a Datastore namespace.
func WithNamespace(parent context.Context, namespace string) context.Context {
return context.WithValue(parent, nsKey{}, namespace)
}
// ctxNamespace returns the active namespace for a context.
// It defaults to "" if no namespace was specified.
func ctxNamespace(ctx context.Context) string {
v, _ := ctx.Value(nsKey{}).(string)
return v
}
// ErrFieldMismatch is returned when a field is to be loaded into a different
// type than the one it was stored from, or when a field is missing or
// unexported in the destination struct.
// StructType is the type of the struct pointed to by the destination argument
// passed to Get or to Iterator.Next.
type ErrFieldMismatch struct {
StructType reflect.Type
FieldName string
Reason string
}
func (e *ErrFieldMismatch) Error() string {
return fmt.Sprintf("datastore: cannot load field %q into a %q: %s",
e.FieldName, e.StructType, e.Reason)
}
func (c *Client) call(ctx context.Context, method string, req, resp proto.Message) error {
return c.client.Call(ctx, c.dataset+"/"+method, req, resp)
}
func keyToProto(k *Key) *pb.Key {
if k == nil {
return nil
}
// TODO(jbd): Eliminate unrequired allocations.
path := []*pb.Key_PathElement(nil)
for {
el := &pb.Key_PathElement{
Kind: proto.String(k.kind),
}
if k.id != 0 {
el.Id = proto.Int64(k.id)
}
if k.name != "" {
el.Name = proto.String(k.name)
}
path = append([]*pb.Key_PathElement{el}, path...)
if k.parent == nil {
break
}
k = k.parent
}
key := &pb.Key{
PathElement: path,
}
if k.namespace != "" {
key.PartitionId = &pb.PartitionId{
Namespace: proto.String(k.namespace),
}
}
return key
}
func protoToKey(p *pb.Key) *Key {
keys := make([]*Key, len(p.GetPathElement()))
for i, el := range p.GetPathElement() {
keys[i] = &Key{
namespace: p.GetPartitionId().GetNamespace(),
kind: el.GetKind(),
id: el.GetId(),
name: el.GetName(),
}
}
for i := 0; i < len(keys)-1; i++ {
keys[i+1].parent = keys[i]
}
return keys[len(keys)-1]
}
// multiKeyToProto is a batch version of keyToProto.
func multiKeyToProto(keys []*Key) []*pb.Key {
ret := make([]*pb.Key, len(keys))
for i, k := range keys {
ret[i] = keyToProto(k)
}
return ret
}
// multiKeyToProto is a batch version of keyToProto.
func multiProtoToKey(keys []*pb.Key) []*Key {
ret := make([]*Key, len(keys))
for i, k := range keys {
ret[i] = protoToKey(k)
}
return ret
}
// multiValid is a batch version of Key.valid. It returns an error, not a
// []bool.
func multiValid(key []*Key) error {
invalid := false
for _, k := range key {
if !k.valid() {
invalid = true
break
}
}
if !invalid {
return nil
}
err := make(MultiError, len(key))
for i, k := range key {
if !k.valid() {
err[i] = ErrInvalidKey
}
}
return err
}
// checkMultiArg checks that v has type []S, []*S, []I, or []P, for some struct
// type S, for some interface type I, or some non-interface non-pointer type P
// such that P or *P implements PropertyLoadSaver.
//
// It returns what category the slice's elements are, and the reflect.Type
// that represents S, I or P.
//
// As a special case, PropertyList is an invalid type for v.
func checkMultiArg(v reflect.Value) (m multiArgType, elemType reflect.Type) {
if v.Kind() != reflect.Slice {
return multiArgTypeInvalid, nil
}
if v.Type() == typeOfPropertyList {
return multiArgTypeInvalid, nil
}
elemType = v.Type().Elem()
if reflect.PtrTo(elemType).Implements(typeOfPropertyLoadSaver) {
return multiArgTypePropertyLoadSaver, elemType
}
switch elemType.Kind() {
case reflect.Struct:
return multiArgTypeStruct, elemType
case reflect.Interface:
return multiArgTypeInterface, elemType
case reflect.Ptr:
elemType = elemType.Elem()
if elemType.Kind() == reflect.Struct {
return multiArgTypeStructPtr, elemType
}
}
return multiArgTypeInvalid, nil
}
// Get loads the entity stored for key into dst, which must be a struct pointer
// or implement PropertyLoadSaver. If there is no such entity for the key, Get
// returns ErrNoSuchEntity.
//
// The values of dst's unmatched struct fields are not modified, and matching
// slice-typed fields are not reset before appending to them. In particular, it
// is recommended to pass a pointer to a zero valued struct on each Get call.
//
// ErrFieldMismatch is returned when a field is to be loaded into a different
// type than the one it was stored from, or when a field is missing or
// unexported in the destination struct. ErrFieldMismatch is only returned if
// dst is a struct pointer.
func (c *Client) Get(ctx context.Context, key *Key, dst interface{}) error {
err := c.get(ctx, []*Key{key}, []interface{}{dst}, nil)
if me, ok := err.(MultiError); ok {
return me[0]
}
return err
}
// GetMulti is a batch version of Get.
//
// dst must be a []S, []*S, []I or []P, for some struct type S, some interface
// type I, or some non-interface non-pointer type P such that P or *P
// implements PropertyLoadSaver. If an []I, each element must be a valid dst
// for Get: it must be a struct pointer or implement PropertyLoadSaver.
//
// As a special case, PropertyList is an invalid type for dst, even though a
// PropertyList is a slice of structs. It is treated as invalid to avoid being
// mistakenly passed when []PropertyList was intended.
func (c *Client) GetMulti(ctx context.Context, keys []*Key, dst interface{}) error {
return c.get(ctx, keys, dst, nil)
}
func (c *Client) get(ctx context.Context, keys []*Key, dst interface{}, opts *pb.ReadOptions) error {
v := reflect.ValueOf(dst)
multiArgType, _ := checkMultiArg(v)
// Sanity checks
if multiArgType == multiArgTypeInvalid {
return errors.New("datastore: dst has invalid type")
}
if len(keys) != v.Len() {
return errors.New("datastore: keys and dst slices have different length")
}
if len(keys) == 0 {
return nil
}
// Go through keys, validate them, serialize then, and create a dict mapping them to their index
multiErr, any := make(MultiError, len(keys)), false
keyMap := make(map[string]int)
pbKeys := make([]*pb.Key, len(keys))
for i, k := range keys {
if !k.valid() {
multiErr[i] = ErrInvalidKey
any = true
} else {
keyMap[k.String()] = i
pbKeys[i] = keyToProto(k)
}
}
if any {
return multiErr
}
req := &pb.LookupRequest{
Key: pbKeys,
ReadOptions: opts,
}
resp := &pb.LookupResponse{}
if err := c.call(ctx, "lookup", req, resp); err != nil {
return err
}
if len(resp.Deferred) > 0 {
// TODO(jbd): Assess whether we should retry the deferred keys.
return errors.New("datastore: some entities temporarily unavailable")
}
if len(keys) != len(resp.Found)+len(resp.Missing) {
return errors.New("datastore: internal error: server returned the wrong number of entities")
}
for _, e := range resp.Found {
k := protoToKey(e.Entity.Key)
index := keyMap[k.String()]
elem := v.Index(index)
if multiArgType == multiArgTypePropertyLoadSaver || multiArgType == multiArgTypeStruct {
elem = elem.Addr()
}
err := loadEntity(elem.Interface(), e.Entity)
if err != nil {
multiErr[index] = err
any = true
}
}
for _, e := range resp.Missing {
k := protoToKey(e.Entity.Key)
multiErr[keyMap[k.String()]] = ErrNoSuchEntity
any = true
}
if any {
return multiErr
}
return nil
}
// Put saves the entity src into the datastore with key k. src must be a struct
// pointer or implement PropertyLoadSaver; if a struct pointer then any
// unexported fields of that struct will be skipped. If k is an incomplete key,
// the returned key will be a unique key generated by the datastore.
func (c *Client) Put(ctx context.Context, key *Key, src interface{}) (*Key, error) {
k, err := c.PutMulti(ctx, []*Key{key}, []interface{}{src})
if err != nil {
if me, ok := err.(MultiError); ok {
return nil, me[0]
}
return nil, err
}
return k[0], nil
}
// PutMulti is a batch version of Put.
//
// src must satisfy the same conditions as the dst argument to GetMulti.
func (c *Client) PutMulti(ctx context.Context, keys []*Key, src interface{}) ([]*Key, error) {
mutation, err := putMutation(keys, src)
if err != nil {
return nil, err
}
// Make the request.
req := &pb.CommitRequest{
Mutation: mutation,
Mode: pb.CommitRequest_NON_TRANSACTIONAL.Enum(),
}
resp := &pb.CommitResponse{}
if err := c.call(ctx, "commit", req, resp); err != nil {
return nil, err
}
// Copy any newly minted keys into the returned keys.
newKeys := make(map[int]int) // Map of index in returned slice to index in response.
ret := make([]*Key, len(keys))
var idx int
for i, key := range keys {
if key.Incomplete() {
// This key will be in the mutation result.
newKeys[i] = idx
idx++
} else {
ret[i] = key
}
}
if len(newKeys) != len(resp.MutationResult.InsertAutoIdKey) {
return nil, errors.New("datastore: internal error: server returned the wrong number of keys")
}
for retI, respI := range newKeys {
ret[retI] = protoToKey(resp.MutationResult.InsertAutoIdKey[respI])
}
return ret, nil
}
func putMutation(keys []*Key, src interface{}) (*pb.Mutation, error) {
v := reflect.ValueOf(src)
multiArgType, _ := checkMultiArg(v)
if multiArgType == multiArgTypeInvalid {
return nil, errors.New("datastore: src has invalid type")
}
if len(keys) != v.Len() {
return nil, errors.New("datastore: key and src slices have different length")
}
if len(keys) == 0 {
return nil, nil
}
if err := multiValid(keys); err != nil {
return nil, err
}
var upsert, insert []*pb.Entity
for i, k := range keys {
val := reflect.ValueOf(src).Index(i)
// If src is an interface slice []interface{}{ent1, ent2}
if val.Kind() == reflect.Interface && val.Elem().Kind() == reflect.Slice {
val = val.Elem()
}
// If src is a slice of ptrs []*T{ent1, ent2}
if val.Kind() == reflect.Ptr && val.Elem().Kind() == reflect.Slice {
val = val.Elem()
}
p, err := saveEntity(k, val.Interface())
if err != nil {
return nil, fmt.Errorf("datastore: Error while saving %v: %v", k.String(), err)
}
if k.Incomplete() {
insert = append(insert, p)
} else {
upsert = append(upsert, p)
}
}
return &pb.Mutation{
InsertAutoId: insert,
Upsert: upsert,
}, nil
}
// Delete deletes the entity for the given key.
func (c *Client) Delete(ctx context.Context, key *Key) error {
err := c.DeleteMulti(ctx, []*Key{key})
if me, ok := err.(MultiError); ok {
return me[0]
}
return err
}
// DeleteMulti is a batch version of Delete.
func (c *Client) DeleteMulti(ctx context.Context, keys []*Key) error {
mutation, err := deleteMutation(keys)
if err != nil {
return err
}
req := &pb.CommitRequest{
Mutation: mutation,
Mode: pb.CommitRequest_NON_TRANSACTIONAL.Enum(),
}
resp := &pb.CommitResponse{}
return c.call(ctx, "commit", req, resp)
}
func deleteMutation(keys []*Key) (*pb.Mutation, error) {
protoKeys := make([]*pb.Key, len(keys))
for i, k := range keys {
if k.Incomplete() {
return nil, fmt.Errorf("datastore: can't delete the incomplete key: %v", k)
}
protoKeys[i] = keyToProto(k)
}
return &pb.Mutation{
Delete: protoKeys,
}, nil
}