在Go中从Python项目加载数据存储实体会导致嵌套的结构片切片错误 [英] Loading datastore entities from Python project in Go leads to nested structs slices of slices error
问题描述
为了性能方面的原因,我在Google的Google AppEngine项目中编写了一个模块,但需要能够读取数据存储中的某些实体。我写出了Go代码以便能够读取我在Python中构建的实体,但出现以下错误:
数据存储:展平嵌套结构导致切片片段:字段消息
Python中的模型定义:
class ModelB(ndb.Model):
msg_id = ndb.StringProperty(indexed = False)
cat_ids = ndb.StringProperty(repeated = True, indexed = False)
list_ids = ndb.StringProperty(repeated = True,indexed = False)
default_list_id_index = ndb.IntegerProperty(indexed = False)
ModelA(ndb.Model ):
date_join = ndb.DateTimeProperty(auto_now_add = True)
name = ndb.StringProperty()
owner_salutation = ndb.StringProperty(indexed = False)
owner_email_address = ndb.StringProperty ()b
logo_url = ndb.StringProperty(indexed = False)
...
messages = ndb.LocalStructuredProperty(ModelB,name ='bm',repeated = True)
在Go中:
type ModelB struct {
MessageID字符串`datastore:msg_id,noindex`
CategoryIDs [] string`datastore:cat_ids,noindex`
ListIDs [] string`datastore:list_ids,noindex`
DefaultListIDIndex int`datastore:default_list_id_index,noindex`
}
type ModelA struct {
DateJoin time.Time`datastore:date_join,`
Name '
OwnerSalutation字符串'datastore:owner_salutation,noindex`
OwnerEmailAddress字符串`datastore:owner_email_address,``
LogoURL字符串`datastore:logo_url, noindex`
Messages [] ModelB`datastore:bm,``
}
有什么我在这里做错了吗?只是Go与Python模型定义之间的功能不兼容?
解码ModelB
重新定义 ModelA
如下:
import pb appengine_internal / datastore
import protocode.google.com/p/goprotobuf/proto
type ModelA struct {
DateJoin time.Time`datastore:date_join, `
名称字符串`datastore:name,
OwnerSalutation字符串`datastore:owner_salutation,noindex`
OwnerEmailAddress字符串`datastore:owner_email_address`
LogoURL字符串`datastore:logo_url,noindex`
消息[] ModelB`datastore: - `
}
// Load为PropertyLoaderSaver接口实现。
func(seller * ModelA)加载(c <-chan datastore.Property)错误{
f:= make(chan datastore.Property,100)
for p:=范围c {
如果p.Name ==bm{
var val pb.EntityProto
err:= proto.Unmarshal([] byte(p.Value。(string)), & val)
if err!= nil {
return err
}
// TODO:将结果存储为新的ModelB
} else {
f < - p
}
}
关闭(f)
返回datastore.LoadStruct(卖家,f)
}
但我收到以下错误:
proto:必填字段{未知}未设置
我猜如果你挖得够多,你会找到答案:
首先,在Python中定义LocalStructuredProperty属性时,需要设置 keep_keys = True
class ModelB(ndb.Model):
msg_id = ndb.StringProperty(indexed = False)
cat_ids = ndb.StringProperty(repeated = True,indexed = False)
list_ids = ndb.StringProperty(repeated = True,indexed = False)
default_list_id_index = ndb.IntegerProperty(indexed = False)
class ModelA(ndb.Model):
date_join = ndb.DateTimeProperty(auto_now_add = True)
name = ndb.StringProperty()
owner_salutation = ndb.StringProperty(indexed =假)
owner_email_address = ndb.StringProperty()
logo_url = ndb.StringProperty(indexed = False)
...
messages = ndb.LocalStructuredProperty(ModelB,name =' bm',repeated = True,keep_keys = True)
在我的代码中进行简单重定义并映射到我的对每个表达式执行 put()
的实体。
然后在我的Go Code中:
type ModelB struct {
MessageID字符串`datastore:msg_id,noindex`
CategoryIDs [] string`datastore :cat_ids,noindex`
ListIDs [] string`datastore:list_ids,noindex`
DefaultListIDIndex int`datastore:default_list_id_index,noindex`
}
type ModelA struct {
DateJoin time.Time`datastore:date_join,`
名称字符串`datastore:name,
OwnerSalutation字符串`datastore:owner_salutation,noindex`
OwnerEmailAddress string` datastore:owner_email_address,`
LogoURL字符串`datastore:logo_url,noindex`
消息[] ModelB`datastore: - `
}
// Load是为PropertyLoaderSaver接口实现的。
func(s * ModelA)Load(c< -chan datastore.Property)(err error){
f:= make(chan datastore.Property,32)
errc:= make chan error,1)
推迟func(){
if err == nil {
err =< -errc
}
}()
去func(){
推迟关闭(f)
为p:=范围c {
如果p.Name ==bm{
var b ModelB
err:= loadLocalStructuredProperty(& b,[] byte(p.Value。(string)))
if err!= nil {
errc < - err
return
}
s.Messages = append(s.Messages,b)
} else {
f< - p
}
}
errc< - nil
}()
返回datastore.LoadStruct(s,f)
}
我必须从 appengine / datastore
包中拷贝一大堆作为关键字f unction未被导出,为了简化我需要复制的代码量,我放弃了对 Reference 类型的支持。我在问题跟踪器上打开了一张票,看看是否可以导出导出的
loadEntity
函数: https://code.google.com/p/googleappengine/issues/detail?id=10426
导入(
错误
时间
appengine
appengine / datastore
pbappengine_internal / datastore
protocode.google.com/p/goprotobuf/proto
)
func loadLocalStructuredProperty(dst interface {},raw_proto [] byte)错误{
var val pb.EntityProto
err:= proto.Unmarshal(raw_proto,& val)
if err!= nil {
返回err
}
返回loadEntity(dst,& val)
}
//从appengine / datastore复制,因为它没有导出
// loadEntity将一个EntityProto加载到PropertyLoadSaver或struct pointe中河
func loadEntity(dst interface {},src * pb.EntityProto)(err error){
c:= make(chan datastore.Property,32)
errc:= make(chan error, 1)
defer func(){
if err == nil {
err =< -errc
}
}()
go protoToProperties c,errc,src)
if e,ok:= dst。(datastore.PropertyLoadSaver); OK {
return e.Load(c)
}
return datastore.LoadStruct(dst,c)
}
func protoToProperties(dst chan< - datastore.Property,errc chan< - error,src * pb.EntityProto){
defer close(dst)
道具,rawProps:= src.Property,src.RawProperty
for {
var(
x * pb.Property
noIndex bool
)
if len(道具)> 0 {
x,props = props [0],props [1:]
} else if len(rawProps)> 0 {
x,rawProps = rawProps [0],rawProps [1:]
noIndex = true
} else {
break
}
var value interface {}
如果x.Meaning!= nil&& * x.Meaning == pb.Property_INDEX_VALUE {
value = indexValue {x.Value}
} else {
var err error
value,err = propValue(x.Value, x.GetMeaning())
if err!= nil {
errc < - err
return
}
}
dst < - datastore。属性{
名称:x.GetName(),
值:value,
NoIndex:noIndex,
Multiple:x.GetMultiple(),
}
errc < - nil
}
从UnixMicro(t int64)time.Time {
return time.Unix(t / 1e6,(t% 1e6)* 1e3)
}
// propValue返回一个Go值,它将原始PropertyValue与
//的含义相结合。例如,具有GD_WHEN的Int64Value将成为time.Time。
func propValue(v * pb.PropertyValue,m pb.Property_Meaning)(interface {},error){
switch {
case v.Int64Value!= nil:
if m == pb.Property_GD_WHEN {
从UnixMicro返回(* v.Int64Value),无
} else {
return * v.Int64Value,nil
}
case v。 BooleanValue!= nil:
return * v.BooleanValue,nil
case v.StringValue!= nil:
if m == pb.Property_BLOB {
return [] byte(* v.StringValue),nil
} else if m == pb.Property_BLOBKEY {
return appengine.BlobKey(* v.StringValue),nil
} else {
return * v .StringValue,nil
}
case v.DoubleValue!= nil:
return * v.DoubleValue,nil
case v.Referencevalue!= nil:
return nil ,errors.New(Not Implemented!)
}
return nil,nil
}
// indexValue是一个属性值,它在创建时实体从
//一个索引(例如投影查询)加载。
//
//这样的属性值不包含所有需要的元数据
//忠实地表示为Go值,而是表示为
//不透明的indexValue。将属性加载到具体的结构类型中(例如通过
//将结构指针传递给Iterator.Next)以重构实际的Go值
//类型为int,string,time.Time等
type indexValue struct {
value * pb.PropertyValue
}
I am writing a module in my Google AppEngine project in Go for performance reasons but need to be able to read from some of the entities I have in datastore. I wrote out the Go code to be able to read the entities I built out in Python but I am getting the following error:
datastore: flattening nested structs leads to a slice of slices: field "Messages"
Model Definitions in Python:
class ModelB(ndb.Model):
msg_id = ndb.StringProperty(indexed=False)
cat_ids = ndb.StringProperty(repeated=True, indexed=False)
list_ids = ndb.StringProperty(repeated=True, indexed=False)
default_list_id_index = ndb.IntegerProperty(indexed=False)
class ModelA(ndb.Model):
date_join = ndb.DateTimeProperty(auto_now_add=True)
name = ndb.StringProperty()
owner_salutation = ndb.StringProperty(indexed=False)
owner_email_address = ndb.StringProperty()
logo_url = ndb.StringProperty(indexed=False)
...
messages = ndb.LocalStructuredProperty(ModelB, name='bm', repeated=True)
And in Go:
type ModelB struct {
MessageID string `datastore:"msg_id,noindex"`
CategoryIDs []string `datastore:"cat_ids,noindex"`
ListIDs []string `datastore:"list_ids,noindex"`
DefaultListIDIndex int `datastore:"default_list_id_index,noindex"`
}
type ModelA struct {
DateJoin time.Time `datastore:"date_join,"`
Name string `datastore:"name,"`
OwnerSalutation string `datastore:"owner_salutation,noindex"`
OwnerEmailAddress string `datastore:"owner_email_address,"`
LogoURL string `datastore:"logo_url,noindex"`
Messages []ModelB `datastore:"bm,"`
}
Is there something I'm doing wrong here? Is just a feature incompatibility between Go vs Python model definitions?
Attempt to Decode ModelB
Re-define ModelA
as follows:
import pb "appengine_internal/datastore"
import proto "code.google.com/p/goprotobuf/proto"
type ModelA struct {
DateJoin time.Time `datastore:"date_join,"`
Name string `datastore:"name,"`
OwnerSalutation string `datastore:"owner_salutation,noindex"`
OwnerEmailAddress string `datastore:"owner_email_address,"`
LogoURL string `datastore:"logo_url,noindex"`
Messages []ModelB `datastore:"-"`
}
// Load is implemented for the PropertyLoaderSaver interface.
func (seller *ModelA) Load(c <-chan datastore.Property) error {
f := make(chan datastore.Property, 100)
for p := range c {
if p.Name == "bm" {
var val pb.EntityProto
err := proto.Unmarshal([]byte(p.Value.(string)), &val)
if err != nil {
return err
}
//TODO: Store result as a new ModelB
} else {
f <- p
}
}
close(f)
return datastore.LoadStruct(seller, f)
}
But I receive the following error:
proto: required field "{Unknown}" not set
I guess if you dig enough you'll find the answer:
First off, when defining the LocalStructuredProperty properties in Python, you need to set keep_keys=True
class ModelB(ndb.Model):
msg_id = ndb.StringProperty(indexed=False)
cat_ids = ndb.StringProperty(repeated=True, indexed=False)
list_ids = ndb.StringProperty(repeated=True, indexed=False)
default_list_id_index = ndb.IntegerProperty(indexed=False)
class ModelA(ndb.Model):
date_join = ndb.DateTimeProperty(auto_now_add=True)
name = ndb.StringProperty()
owner_salutation = ndb.StringProperty(indexed=False)
owner_email_address = ndb.StringProperty()
logo_url = ndb.StringProperty(indexed=False)
...
messages = ndb.LocalStructuredProperty(ModelB, name='bm', repeated=True, keep_keys=True)
A simple redefinition in my code and mapping over my entities doing a put()
on each fixed up the representation.
Then in my Go Code:
type ModelB struct {
MessageID string `datastore:"msg_id,noindex"`
CategoryIDs []string `datastore:"cat_ids,noindex"`
ListIDs []string `datastore:"list_ids,noindex"`
DefaultListIDIndex int `datastore:"default_list_id_index,noindex"`
}
type ModelA struct {
DateJoin time.Time `datastore:"date_join,"`
Name string `datastore:"name,"`
OwnerSalutation string `datastore:"owner_salutation,noindex"`
OwnerEmailAddress string `datastore:"owner_email_address,"`
LogoURL string `datastore:"logo_url,noindex"`
Messages []ModelB `datastore:"-"`
}
// Load is implemented for the PropertyLoaderSaver interface.
func (s *ModelA) Load(c <-chan datastore.Property) (err error) {
f := make(chan datastore.Property, 32)
errc := make(chan error, 1)
defer func() {
if err == nil {
err = <-errc
}
}()
go func() {
defer close(f)
for p := range c {
if p.Name == "bm" {
var b ModelB
err := loadLocalStructuredProperty(&b, []byte(p.Value.(string)))
if err != nil {
errc <- err
return
}
s.Messages = append(s.Messages, b)
} else {
f <- p
}
}
errc <- nil
}()
return datastore.LoadStruct(s, f)
}
I had to copy a bunch from the appengine/datastore
package as a key function wasn't exported and to simplify the amount of code I needed to copy, I dropped support for Reference
types. I opened a ticket on the issue tracker to see if we can get the loadEntity
function exported: https://code.google.com/p/googleappengine/issues/detail?id=10426
import (
"errors"
"time"
"appengine"
"appengine/datastore"
pb "appengine_internal/datastore"
proto "code.google.com/p/goprotobuf/proto"
)
func loadLocalStructuredProperty(dst interface{}, raw_proto []byte) error {
var val pb.EntityProto
err := proto.Unmarshal(raw_proto, &val)
if err != nil {
return err
}
return loadEntity(dst, &val)
}
//Copied from appengine/datastore since its not exported
// loadEntity loads an EntityProto into PropertyLoadSaver or struct pointer.
func loadEntity(dst interface{}, src *pb.EntityProto) (err error) {
c := make(chan datastore.Property, 32)
errc := make(chan error, 1)
defer func() {
if err == nil {
err = <-errc
}
}()
go protoToProperties(c, errc, src)
if e, ok := dst.(datastore.PropertyLoadSaver); ok {
return e.Load(c)
}
return datastore.LoadStruct(dst, c)
}
func protoToProperties(dst chan<- datastore.Property, errc chan<- error, src *pb.EntityProto) {
defer close(dst)
props, rawProps := src.Property, src.RawProperty
for {
var (
x *pb.Property
noIndex bool
)
if len(props) > 0 {
x, props = props[0], props[1:]
} else if len(rawProps) > 0 {
x, rawProps = rawProps[0], rawProps[1:]
noIndex = true
} else {
break
}
var value interface{}
if x.Meaning != nil && *x.Meaning == pb.Property_INDEX_VALUE {
value = indexValue{x.Value}
} else {
var err error
value, err = propValue(x.Value, x.GetMeaning())
if err != nil {
errc <- err
return
}
}
dst <- datastore.Property{
Name: x.GetName(),
Value: value,
NoIndex: noIndex,
Multiple: x.GetMultiple(),
}
}
errc <- nil
}
func fromUnixMicro(t int64) time.Time {
return time.Unix(t/1e6, (t%1e6)*1e3)
}
// propValue returns a Go value that combines the raw PropertyValue with a
// meaning. For example, an Int64Value with GD_WHEN becomes a time.Time.
func propValue(v *pb.PropertyValue, m pb.Property_Meaning) (interface{}, error) {
switch {
case v.Int64Value != nil:
if m == pb.Property_GD_WHEN {
return fromUnixMicro(*v.Int64Value), nil
} else {
return *v.Int64Value, nil
}
case v.BooleanValue != nil:
return *v.BooleanValue, nil
case v.StringValue != nil:
if m == pb.Property_BLOB {
return []byte(*v.StringValue), nil
} else if m == pb.Property_BLOBKEY {
return appengine.BlobKey(*v.StringValue), nil
} else {
return *v.StringValue, nil
}
case v.DoubleValue != nil:
return *v.DoubleValue, nil
case v.Referencevalue != nil:
return nil, errors.New("Not Implemented!")
}
return nil, nil
}
// indexValue is a Property value that is created when entities are loaded from
// an index, such as from a projection query.
//
// Such Property values do not contain all of the metadata required to be
// faithfully represented as a Go value, and are instead represented as an
// opaque indexValue. Load the properties into a concrete struct type (e.g. by
// passing a struct pointer to Iterator.Next) to reconstruct actual Go values
// of type int, string, time.Time, etc.
type indexValue struct {
value *pb.PropertyValue
}
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