Function DiffMigration

backend/plugin/schema/schema.go:302–323

DiffMigration computes the migration SQL between two database metadata states. Engines may register a metadata migration to avoid round-tripping synced metadata through SDL text. Otherwise, engines with DiffSDLMigration registered convert both sides to SDL and diff. The legacy MetadataDiff + Generat

(engine storepb.Engine, oldSchema, newSchema *model.DatabaseMetadata)

// convert both sides to SDL and diff. The legacy MetadataDiff + GenerateMigration
// path remains the fallback for engines that haven't migrated yet.
func DiffMigration(engine storepb.Engine, oldSchema, newSchema *model.DatabaseMetadata) (string, error) {
	if f, ok := diffMetadataMigrations[engine]; ok {
		return f(oldSchema, newSchema)
	}
	if _, ok := diffSDLMigrations[engine]; ok {
		sourceSDL, err := MetadataToSDL(engine, oldSchema)
		if err != nil {
			return "", errors.Wrap(err, "failed to convert source schema to SDL")
		}
		targetSDL, err := MetadataToSDL(engine, newSchema)
		if err != nil {
			return "", errors.Wrap(err, "failed to convert target schema to SDL")
		}
		return DiffSDLMigration(engine, sourceSDL, targetSDL)
	}
	// Fallback to legacy path for engines that haven't migrated yet.
	diff, err := GetDatabaseSchemaDiff(engine, oldSchema, newSchema)
	if err != nil {
		return "", err
	}
	return GenerateMigration(engine, diff)
}

func RegisterDiffMetadataMigration(engine storepb.Engine, f diffMetadataMigration) {
	mux.Lock()