sqldb: establish a base DB version even if it's not yet tracked

Previously, if a DB version wasn't available, we re-ran all schema
migrations without verifying the schema version. However, setting a
base schema version is essential because some earlier migrations were
not idempotent. This commit addresses the issue by using the current
schema version provided by sqlc as the base.

sqldb/migrations.go

@@ -112,6 +112,9 @@ type MigrationExecutor interface {
 	// order. Migration details are stored in the global variable
 	// migrationConfig.
 	ExecuteMigrations(target MigrationTarget) error
+
+	// GetSchemaVersion returns the current schema version of the database.
+	GetSchemaVersion() (int, bool, error)
 }
 
 var (
@@ -360,6 +363,22 @@ func ApplyMigrations(ctx context.Context, db *BaseDB,
 		}
 
 		currentVersion = int(version)
+	} else {
+		// Since we don't have a version tracked by our own table yet,
+		// we'll use the schema version reported by sqlc to determine
+		// the current version.
+		//
+		// NOTE: This is safe because the first in-code migration was
+		// introduced in version 7. This is only possible if the user
+		// has a schema version <= 4.
+		var dirty bool
+		currentVersion, dirty, err = migrator.GetSchemaVersion()
+		if err != nil {
+			return err
+		}
+
+		log.Infof("No database version found, using schema version %d "+
+			"(dirty=%v) as base version", currentVersion, dirty)
 	}
 
 	for _, migration := range migrations {

sqldb/postgres.go

@@ -158,6 +158,10 @@ func (s *PostgresStore) ApplyAllMigrations(ctx context.Context,
 	return ApplyMigrations(ctx, s.BaseDB, s, migrations)
 }
 
+func errPostgresMigration(err error) error {
+	return fmt.Errorf("error creating postgres migration: %w", err)
+}
+
 // ExecuteMigrations runs migrations for the Postgres database, depending on the
 // target given, either all migrations or up to a given version.
 func (s *PostgresStore) ExecuteMigrations(target MigrationTarget) error {
@@ -168,7 +172,7 @@ func (s *PostgresStore) ExecuteMigrations(target MigrationTarget) error {
 
 	driver, err := pgx_migrate.WithInstance(s.DB, &pgx_migrate.Config{})
 	if err != nil {
-		return fmt.Errorf("error creating postgres migration: %w", err)
+		return errPostgresMigration(err)
 	}
 
 	// Populate the database with our set of schemas based on our embedded
@@ -178,3 +182,19 @@ func (s *PostgresStore) ExecuteMigrations(target MigrationTarget) error {
 		postgresFS, driver, "sqlc/migrations", dbName, target,
 	)
 }
+
+// GetSchemaVersion returns the current schema version of the Postgres database.
+func (s *PostgresStore) GetSchemaVersion() (int, bool, error) {
+	driver, err := pgx_migrate.WithInstance(s.DB, &pgx_migrate.Config{})
+	if err != nil {
+		return 0, false, errPostgresMigration(err)
+
+	}
+
+	version, dirty, err := driver.Version()
+	if err != nil {
+		return 0, false, err
+	}
+
+	return version, dirty, nil
+}

sqldb/sqlite.go

@@ -158,6 +158,10 @@ func (s *SqliteStore) ApplyAllMigrations(ctx context.Context,
 	return ApplyMigrations(ctx, s.BaseDB, s, migrations)
 }
 
+func errSqliteMigration(err error) error {
+	return fmt.Errorf("error creating sqlite migration: %w", err)
+}
+
 // ExecuteMigrations runs migrations for the sqlite database, depending on the
 // target given, either all migrations or up to a given version.
 func (s *SqliteStore) ExecuteMigrations(target MigrationTarget) error {
@@ -165,7 +169,7 @@ func (s *SqliteStore) ExecuteMigrations(target MigrationTarget) error {
 		s.DB, &sqlite_migrate.Config{},
 	)
 	if err != nil {
-		return fmt.Errorf("error creating sqlite migration: %w", err)
+		return errSqliteMigration(err)
 	}
 
 	// Populate the database with our set of schemas based on our embedded
@@ -176,6 +180,23 @@ func (s *SqliteStore) ExecuteMigrations(target MigrationTarget) error {
 	)
 }
 
+// GetSchemaVersion returns the current schema version of the SQLite database.
+func (s *SqliteStore) GetSchemaVersion() (int, bool, error) {
+	driver, err := sqlite_migrate.WithInstance(
+		s.DB, &sqlite_migrate.Config{},
+	)
+	if err != nil {
+		return 0, false, errSqliteMigration(err)
+	}
+
+	version, dirty, err := driver.Version()
+	if err != nil {
+		return 0, dirty, err
+	}
+
+	return version, dirty, nil
+}
+
 // NewTestSqliteDB is a helper function that creates an SQLite database for
 // testing.
 func NewTestSqliteDB(t *testing.T) *SqliteStore {