How Can GORM's Preload Function Efficiently Fetch Related Records in Go?

GORM Golang ORM Associations: Preloading Related Records

GORM is a popular ORM for Go that simplifies database operations. When working with ORM, managing associations between related records is essential. In this context, we'll explore how to efficiently retrieve related records using GORM's preloading feature.

Consider a scenario where we have two structs: Place and Town. Each Place belongs to a single Town, and each Town has multiple Places.

type Place struct {
  ID          int
  Name        string
  Town        Town
}

type Town struct {
  ID   int
  Name string
}

To fetch all Places and eagerly load the corresponding Town for each Place, we can use the Preload function:

db.Preload("Town").Find(&places)

This single line of code executes two queries: one to fetch all Places and another to fetch all Towns that have a matching Place. The resulting slice of Place structs will have the Town field populated.

fmt.Println(places)
// Output: [{1 Place1  {1 Town1}} {2 Place2  {1 Town1}}]

This approach is efficient because it avoids the N 1 problem, which occurs when you need to execute N additional queries to retrieve related records. Preloading allows us to retrieve all the necessary data in just two queries, making it more efficient for larger datasets.

The above is the detailed content of How Can GORM's Preload Function Efficiently Fetch Related Records in Go?. For more information, please follow other related articles on the PHP Chinese website!