How to Store Nested Structs in GAE Datastore with Go: A Solution for Efficient Data Handling

Storing Nested Structs in GAE Datastore with Go

The Google App Engine Datastore provides limited support for nested structures in Go. This article explores a solution to achieve nested struct storage in the datastore.

Problem

When sending a post to a user as JSON, the need arises to include user information along with the post. The traditional method of storing two fields (one for the user ID and one for the user struct) seems redundant. The question arises: Is there a more efficient solution?

Solution

Go's appengine datastore API provides the PropertyLoadSaver interface to address this issue. This interface allows users to define custom serialization and deserialization logic for their structs.

By implementing the Load and Save methods of this interface, you gain complete control over how your data is structured and serialized. This flexibility enables you to store nested structs effectively while still allowing filtering and indexing on individual fields.

Implementation

1. Define your structs as desired.

2. Implement the PropertyLoadSaver interface for each struct:

   • In the Load method, you can populate your struct from a PropertyMap.
   • In the Save method, you can serialize your struct into a PropertyMap.

Output JSON

The resulting JSON output will retain the desired nested structure:

<code class="json">{
  "POST": {
    "field1": "value1",
    "field2": "value2",
    "USER": {
      "user_field1": "value3",
      "user_Field2": "value4"
    }
  }
}</code>

This approach provides a tailored solution for storing nested structs in the GAE datastore, ensuring both data integrity and efficient data handling.

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