Group seeders with tags and run only matching seeders using RunByTag or the CLI --tag flag.

Seeder Tags

New in v1.0.0: Seeder tags, the TaggedSeeder interface, RunByTag(), and the --tag CLI flag are all introduced in v1.0.0.

Tags let you group seeders by purpose — like "development", "testing", or "production" — and run only the seeders that match a specific tag.

The TaggedSeeder Interface

Implement the TaggedSeeder interface to assign tags to a seeder:

type TaggedSeeder interface {
    Seeder
    Tags() []string
}

Method	Signature	Description
`Tags`	`Tags() []string`	Returns the tags this seeder belongs to

A seeder can have multiple tags. The TaggedSeeder interface extends the base Seeder interface, so you still need to implement Run.

Defining a Tagged Seeder

seeders/dev_user_seeder.go

package seeders

import (
    "database/sql"
)

type DevUserSeeder struct{}

func (s *DevUserSeeder) Tags() []string {
    return []string{"development", "testing"}
}

func (s *DevUserSeeder) Run(db *sql.DB) error {
    _, err := db.Exec(
        "INSERT INTO users (name, email) VALUES ($1, $2)",
        "Dev User", "dev@example.com",
    )
    return err
}

This seeder runs when either the "development" or "testing" tag is requested.

Running Seeders by Tag

Programmatic API

Use runner.RunByTag() to execute only seeders matching a specific tag:

runner := seeder.NewRunner(db)

runner.Register("DevUserSeeder", &seeders.DevUserSeeder{})
runner.Register("ProdDefaultsSeeder", &seeders.ProdDefaultsSeeder{})
runner.Register("TestFixtureSeeder", &seeders.TestFixtureSeeder{})

// Run only seeders tagged "development"
if err := runner.RunByTag("development"); err != nil {
    log.Fatal(err)
}

CLI

Use the --tag flag with the db:seed command:

bash

# Run only seeders tagged "development"
go-migration db:seed --tag=development

# Run only seeders tagged "testing"
go-migration db:seed --tag=testing

Seeders Without Tags

The TaggedSeeder interface is optional. Seeders that don't implement it:

Run normally with runner.RunAll() and runner.Run()
Are skipped by runner.RunByTag() — only tagged seeders are considered

// This seeder has no tags — it runs with RunAll() but not RunByTag()
type RoleSeeder struct{}

func (s *RoleSeeder) Run(db *sql.DB) error {
    _, err := db.Exec("INSERT INTO roles (name) VALUES ($1)", "admin")
    return err
}

RunByTag only considers seeders that implement TaggedSeeder. Untagged seeders are silently skipped, not treated as errors.

Complete Example

main.go

package main

import (
    "database/sql"
    "log"

    _ "github.com/lib/pq"

    "github.com/gopackx/go-migration/seeder"
    "your-project/seeders"
)

func main() {
    db, err := sql.Open("postgres", "postgres://user:password@localhost:5432/mydb?sslmode=disable")
    if err != nil {
        log.Fatal(err)
    }
    defer db.Close()

    runner := seeder.NewRunner(db)

    runner.Register("DevUserSeeder", &seeders.DevUserSeeder{})       // tags: development, testing
    runner.Register("ProdDefaultsSeeder", &seeders.ProdDefaultsSeeder{}) // tags: production
    runner.Register("RoleSeeder", &seeders.RoleSeeder{})             // no tags

    // Run only development seeders
    if err := runner.RunByTag("development"); err != nil {
        log.Fatal(err)
    }

    log.Println("Development seeders complete!")
}

What's Next?

Seeder Rollback — undo seeded data with rollback support
Batch Insert — insert large datasets efficiently

Seeder Tags

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