/
migrate.go
123 lines (102 loc) · 2.76 KB
/
migrate.go
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package postgres
import (
"fmt"
"time"
"gorm.io/gorm"
)
// Migration is used to hold the database key and function for creating the migration.
type Migration struct {
Executor func(*gorm.DB) error
Key string
}
func (m Migration) execute(db *gorm.DB) error {
// Start transaction
tx := db.Begin()
if tx.Error != nil {
return tx.Error
}
// Run migration logic
if err := m.Executor(tx); err != nil {
tx.Rollback()
return err
}
// Commit transaction
if err := tx.Commit().Error; err != nil {
tx.Rollback()
return err
}
return nil
}
func MigrateUp(db *gorm.DB, migrations []Migration) error {
// Ensure public schema exists
ensurePublicSchema(db)
// Ensure migrations table exists
ensureMigrationsTable(db)
// Run migrations
migrationsToRun := determineMigrationsToRun(db, migrations)
for _, m := range migrationsToRun {
if err := m.execute(db); err != nil {
fmt.Println(m.Key)
panic(err)
}
// There was no error, so create a record for the migration
createMigrationRecord(db, m.Key)
}
return nil
}
func ensurePublicSchema(db *gorm.DB) {
err := db.Exec("CREATE SCHEMA IF NOT EXISTS public;").Error
if err != nil {
panic(fmt.Sprintf("Error creating public schema. Cannot continue: %s", err))
}
}
func ensureMigrationsTable(db *gorm.DB) {
err := db.Exec(`
CREATE TABLE IF NOT EXISTS migrations (
id SERIAL PRIMARY KEY,
ran_at bigint,
key text,
CONSTRAINT migrations_key UNIQUE (key)
)
`).Error
if err != nil {
panic(fmt.Sprintf("Error creating migrations table. Cannot continue: %s", err))
}
}
type migrationKeyCol struct {
Key string
}
func determineMigrationsToRun(db *gorm.DB, allMigrations []Migration) []Migration {
ranMigrations := []migrationKeyCol{}
r := db.Raw("SELECT key FROM migrations;")
if r.Error != nil {
panic(fmt.Sprintf("Error fetching ran migrations. Cannot continue: %s", r.Error))
}
r.Scan(&ranMigrations)
// If key is empty, we haven't ran *any* migrations
if len(ranMigrations) == 0 {
return allMigrations
}
// Compare ran migration keys to all migration keys to determine which need to run
migrationsToRun := []Migration{}
for _, migrationToCheck := range allMigrations {
itsBeenRun := false
// If this migration has already ran, continue to next iteration (don't add to list to run)
for _, ranMigration := range ranMigrations {
if migrationToCheck.Key == ranMigration.Key {
itsBeenRun = true
continue
}
}
if !itsBeenRun {
migrationsToRun = append(migrationsToRun, migrationToCheck)
}
}
return migrationsToRun
}
func createMigrationRecord(db *gorm.DB, key string) {
err := db.Exec(`INSERT INTO migrations (key, ran_at) VALUES (?, ?)`, key, time.Now().Unix()).Error
if err != nil {
panic(fmt.Sprintf("Error creating migration. Cannot continue: %s", err))
}
}