How Can SQLx Efficiently Handle Nested Struct Scanning in Database Queries?

Nested Struct Scanning with SQLx

In the realm of database manipulations, scanning nested structs into database entities can pose a challenge. Let's consider the following scenario:

Given the DB Model:

type Customer struct {
   Id      int     `json:"id" db:"id"`
   Name    string  `json:"name" db:"name"`
   Address Address `json:"adress"`
}

type Address struct {
   Street string `json:"street" db:"street"`
   City   string `json:"city" db:"city"`
}

The Conundrum:

Attempting to populate the Customer struct using the following code fails with an error indicating that the street destination field in *models.Customer is missing.

customer := models.Customer{}
err := db.Get(&customer, `select * from users where>

The Solution:

SQLx provides a powerful solution for scanning nested structs through the use of embedded structs. Instead of declaring Address as a field with individual db tags, we can embed it into Customer:

type Customer struct {
   Id     int    `json:"id" db:"id"`
   Name   string `json:"name" db:"name"`
   Address
}

By embedding the struct, the Address fields are promoted into Customer and receive their db tags from their parent. SQLx will then populate these fields directly from the query result.

Important Note:

While this approach simplifies scanning, it also flattens the JSON output of the struct. To preserve the original nested structure, consider remapping the database struct to your target type.

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