Flatten vs nested serialization

datastore.go

package main

import (
	"encoding/json"
	"fmt"

	"cloud.google.com/go/datastore"
)

type Other struct {
	Text string
}
type Nested struct {
	Other  Other
	Others []Other
}
type Flatten struct {
	Other  Other   `datastore:",flatten"`
	Others []Other `datastore:",flatten"`
}

func main() {
	nested := Nested{Other{"X"}, []Other{{"Y"}, {"Z"}}}
	flatten := Flatten{Other{"X"}, []Other{{"Y"}, {"Z"}}}

	psn, _ := datastore.SaveStruct(&nested)
	psf, _ := datastore.SaveStruct(&flatten)

	bsn, _ := json.MarshalIndent(psn, "", " ")
	fmt.Println(string(bsn))

	bsf, _ := json.MarshalIndent(psf, "", " ")
	fmt.Println(string(bsf))
}

output.md

Nested

[
 {
  "Name": "Other",
  "Value": {
   "Key": null,
   "Properties": [
    {
     "Name": "Text",
     "Value": "X",
     "NoIndex": false
    }
   ]
  },
  "NoIndex": false
 },
 {
  "Name": "Others",
  "Value": [
   {
    "Key": null,
    "Properties": [
     {
      "Name": "Text",
      "Value": "Y",
      "NoIndex": false
     }
    ]
   },
   {
    "Key": null,
    "Properties": [
     {
      "Name": "Text",
      "Value": "Z",
      "NoIndex": false
     }
    ]
   }
  ],
  "NoIndex": false
 }
]

Flatten

[
 {
  "Name": "Other.Text",
  "Value": "X",
  "NoIndex": false
 },
 {
  "Name": "Others.Text",
  "Value": [
   "Y",
   "Z"
  ],
  "NoIndex": false
 }
]