micro/go-micro · critical

Couldn't use database

Error message

Couldn't use database

What it means

During initDB (called from configure) the store executes `USE <database>` on the freshly opened MySQL connection; failure here means the database does not exist, the user lacks permission, or the connection itself is broken. The store cannot scope its tables without selecting the database.

Source

Thrown at store/mysql/mysql.go:151

	}
	_, err = result.RowsAffected()
	if err != nil {
		return err
	}

	return nil
}

func (s *sqlStore) initDB() error {
	// Create the namespace's database
	_, err := s.db.Exec(fmt.Sprintf("CREATE DATABASE IF NOT EXISTS %s ;", s.database))
	if err != nil {
		return err
	}

	_, err = s.db.Exec(fmt.Sprintf("USE %s ;", s.database))
	if err != nil {
		return errors.Wrap(err, "Couldn't use database")
	}

	// Create a table for the namespace's prefix
	createSQL := fmt.Sprintf("CREATE TABLE IF NOT EXISTS %s (`key` varchar(255) primary key, value blob null, expiry timestamp not null);", s.table)
	_, err = s.db.Exec(createSQL)
	if err != nil {
		return errors.Wrap(err, "Couldn't create table")
	}

	// prepare statements
	var prepareErr error

	s.readPrepare, prepareErr = s.db.Prepare(fmt.Sprintf("SELECT `key`, value, expiry FROM %s.%s WHERE `key` = ?;", s.database, s.table))
	if prepareErr != nil {
		return errors.Wrap(prepareErr, "failed to prepare read statement")
	}

	s.writePrepare, prepareErr = s.db.Prepare(fmt.Sprintf("INSERT INTO %s.%s (`key`, value, expiry) VALUES(?, ?, ?) ON DUPLICATE KEY UPDATE `value`= ?, `expiry` = ?", s.database, s.table))

View on GitHub (pinned to 24529f1404)

Solutions

1. Create the database: CREATE DATABASE <name>;
2. Verify the database name in store options/environment matches an existing schema
3. Grant privileges: GRANT ALL ON <db>.* TO '<user>'@'%';
4. Test MySQL connectivity and credentials with the mysql CLI using the same DSN

Example fix

// before
store := mysql.NewStore(store.Database("missing_db"))
// after
// mysql: CREATE DATABASE micro_db;
store := mysql.NewStore(store.Database("micro_db"))

// run before configuring the store
rows, err := db.Query("SELECT SCHEMA_NAME FROM information_schema.SCHEMATA WHERE SCHEMA_NAME = ?", dbName)
if err != nil || !rows.Next() {
    return fmt.Errorf("database %s missing or not accessible", dbName)
}

When it happens

Trigger: store configuration (namespace/database option) names a database that was never created, the MySQL user lacks privileges on it, or the TCP connection to MySQL failed silently; surfaced via configure() during store Init/newStore.

Common situations: Wrong DB name in store options or MYSQL_DATABASE env var; migration scripts never created the database; MySQL user granted no rights on the target schema; connection dropped between dial and USE.

Related errors

• Couldn't create table
• Couldn't insert record ${key}
• failed to prepare read statement
• failed to prepare write statement
• failed to prepare delete statement

AI-assisted analysis of micro/go-micro@24529f1404 (2026-09-01). Data as JSON: /api/errors/9fadceacf94f7283. Report an issue: GitHub.