Boostport/migration

package mysql

import (
    "database/sql"
    "errors"
    "fmt"
    "strings"

    m "github.com/Boostport/migration"
    "github.com/Boostport/migration/parser"
    "github.com/go-sql-driver/mysql"
)

// Driver is the mysql migration.Driver implementation
type Driver struct {
    db *sql.DB
}

const mysqlTableName = "schema_migration"

// New creates a new Driver driver.
// The DSN is documented here: https://github.com/go-sql-driver/mysql#dsn-data-source-name
func New(dsn string) (m.Driver, error) {
    parsedDSN, err := mysql.ParseDSN(dsn)
    if err != nil {
        return nil, err
    }

    parsedDSN.MultiStatements = true
    db, err := sql.Open("mysql", parsedDSN.FormatDSN())
    if err != nil {
        return nil, err
    }
    if err := db.Ping(); err != nil {
        return nil, err
    }

    d := &Driver{
        db: db,
    }
    if err := d.ensureVersionTableExists(); err != nil {
        return nil, err
    }
    return d, nil
}

// NewFromDB returns a mysql driver from a sql.DB
func NewFromDB(db *sql.DB) (m.Driver, error) {
    if _, ok := db.Driver().(*mysql.MySQLDriver); !ok {
        return nil, errors.New("database instance is not using the MySQL driver")
    }

    if err := db.Ping(); err != nil {
        return nil, err
    }

    d := &Driver{
        db: db,
    }
    if err := d.ensureVersionTableExists(); err != nil {
        return nil, err
    }
    return d, nil
}

// Close closes the connection to the Driver server.
func (driver *Driver) Close() error {
    err := driver.db.Close()
    return err
}

func (driver *Driver) ensureVersionTableExists() error {
    _, err := driver.db.Exec("CREATE TABLE IF NOT EXISTS " + mysqlTableName + " (version varchar(255) not null primary key)")
    return err
}

// Migrate runs a migration.
func (driver *Driver) Migrate(migration *m.PlannedMigration) error {
    // Note: Driver does not support DDL statements in a transaction. If DDL statements are
    // executed in a transaction, it is an implicit commit.
    // See: http://dev.mysql.com/doc/refman/5.7/en/implicit-commit.html
    var migrationStatements *parser.ParsedMigration

    if migration.Direction == m.Up {
        migrationStatements = migration.Up
    } else if migration.Direction == m.Down {
        migrationStatements = migration.Down
    }

    for _, sqlStmt := range migrationStatements.Statements {
        if len(strings.TrimSpace(sqlStmt)) > 0 {
            if _, err := driver.db.Exec(sqlStmt); err != nil {
                return fmt.Errorf("Error executing statement: %s\n%s", err, sqlStmt)
            }
        }
    }

    if migration.Direction == m.Up {
        if _, err := driver.db.Exec("INSERT INTO "+mysqlTableName+" (version) VALUES (?)", migration.ID); err != nil {
            return err
        }
    } else {
        if _, err := driver.db.Exec("DELETE FROM "+mysqlTableName+" WHERE version=?", migration.ID); err != nil {
            return err
        }
    }

    return nil
}

// Versions lists all the applied versions.
func (driver *Driver) Versions() ([]string, error) {
    var versions []string

    rows, err := driver.db.Query("SELECT version FROM " + mysqlTableName + " ORDER BY version DESC")
    if err != nil {
        return versions, err
    }

    defer func() {
        _ = rows.Close()
    }()

    for rows.Next() {
        var version string
        err = rows.Scan(&version)
        if err != nil {
            return versions, err
        }
        versions = append(versions, version)
    }

    err = rows.Err()

    return versions, err
}