Writing Migrations

Structure

Each migration file is a Go file in internal/migrations/ with:

An init() function that registers the migration with the migrator
An up function that applies schema changes
A down function that reverts schema changes

Registration

func init() {
    migration.GetMigrator().AddMigration(&migration.Migration{
        Version: "20250706000001",
        Up:      mig_users_up,
        Down:    mig_users_down,
    })
}

The version should be a timestamp-based string (format: YYYYMMDDHHMMSS). The CLI auto-generates this when you run:

lemmego g migration create_users_table

Writing Up Migrations

Create Table

func mig_up(tx *sql.Tx) error {
    schema := migration.Create("users", func(t *migration.Table) {
        t.BigIncrements("id")
        t.String("name").NotNull()
        t.String("email").Unique()
        t.String("password").NotNull()
        t.Timestamps()
    }).Build()
    _, err := tx.Exec(schema)
    return err
}

Alter Table

func mig_up(tx *sql.Tx) error {
    schema := migration.Alter("users", func(t *migration.Table) {
        t.String("phone").Nullable().After("email")
        t.Boolean("is_verified").Default(false)
    }).Build()
    _, err := tx.Exec(schema)
    return err
}

Drop Table

func mig_up(tx *sql.Tx) error {
    _, err := tx.Exec(migration.Drop("old_sessions"))
    return err
}

Foreign Keys

func mig_up(tx *sql.Tx) error {
    schema := migration.Create("posts", func(t *migration.Table) {
        t.BigIncrements("id")
        t.String("title").NotNull()
        t.Text("body")
        t.ForeignID("user_id").Constrained()
        t.Timestamps()
    }).Build()
    _, err := tx.Exec(schema)
    return err
}

With Indexes

func mig_up(tx *sql.Tx) error {
    schema := migration.Create("posts", func(t *migration.Table) {
        t.BigIncrements("id")
        t.String("slug").Unique()
        t.String("status")
        t.Index("status")
    }).Build()
    _, err := tx.Exec(schema)
    return err
}

Writing Down Migrations

The down function should revert what the up function did:

func mig_down(tx *sql.Tx) error {
    _, err := tx.Exec(migration.Drop("posts"))
    return err
}

Or for alter operations:

func mig_down(tx *sql.Tx) error {
    schema := migration.Alter("users", func(t *migration.Table) {
        t.DropColumn("phone")
    }).Build()
    _, err := tx.Exec(schema)
    return err
}

Complete Example

package migrations

import (
    "database/sql"
    "github.com/lemmego/migration"
)

func init() {
    migration.GetMigrator().AddMigration(&migration.Migration{
        Version: "20250706000001",
        Up:      mig_users_up,
        Down:    mig_users_down,
    })
}

func mig_users_up(tx *sql.Tx) error {
    schema := migration.Create("users", func(t *migration.Table) {
        t.BigIncrements("id")
        t.String("name").NotNull()
        t.String("email").Unique().NotNull()
        t.String("password").NotNull()
        t.Timestamps()
        t.SoftDeletes()
    }).Build()
    _, err := tx.Exec(schema)
    return err
}

func mig_users_down(tx *sql.Tx) error {
    _, err := tx.Exec(migration.Drop("users"))
    return err
}

Column Types Reference Running Migrations