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postgres.go
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postgres.go
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package postgres
import (
"database/sql"
"fmt"
m "github.com/Boostport/migration"
"github.com/Boostport/migration/parser"
_ "github.com/lib/pq"
)
type Driver struct {
db *sql.DB
}
const postgresTableName = "schema_migration"
// NewPostgres creates a new Driver driver.
// The DSN is documented here: https://godoc.org/github.com/lib/pq#hdr-Connection_String_Parameters
func New(dsn string) (m.Driver, error) {
db, err := sql.Open("postgres", dsn)
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
}
// 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 " + postgresTableName + " (version varchar(255) not null primary key)")
return err
}
// Migrate runs a migration.
func (driver *Driver) Migrate(migration *m.PlannedMigration) (err error) {
var (
migrationStatements *parser.ParsedMigration
insertVersion string
)
if migration.Direction == m.Up {
migrationStatements = migration.Up
insertVersion = "INSERT INTO " + postgresTableName + " (version) VALUES ($1)"
} else if migration.Direction == m.Down {
migrationStatements = migration.Down
insertVersion = "DELETE FROM " + postgresTableName + " WHERE version=$1"
}
if migrationStatements.UseTransaction {
tx, err := driver.db.Begin()
if err != nil {
return err
}
defer func() {
if err != nil {
if errRb := tx.Rollback(); errRb != nil {
err = fmt.Errorf("Error rolling back: %s\n%s", errRb, err)
}
return
}
err = tx.Commit()
}()
for _, statement := range migrationStatements.Statements {
if _, err = tx.Exec(statement); err != nil {
return fmt.Errorf("Error executing statement: %s\n%s", err, migrationStatements)
}
}
if _, err = tx.Exec(insertVersion, migration.ID); err != nil {
return fmt.Errorf("Error updating migration versions: %s", err)
}
} else {
for _, statement := range migrationStatements.Statements {
if _, err := driver.db.Exec(statement); err != nil {
return fmt.Errorf("Error executing statement: %s\n%s", err, migrationStatements)
}
}
if _, err = driver.db.Exec(insertVersion, migration.ID); err != nil {
return fmt.Errorf("Error updating migration versions: %s", err)
}
}
return
}
// Versions lists all the applied versions.
func (driver *Driver) Versions() ([]string, error) {
versions := []string{}
rows, err := driver.db.Query("SELECT version FROM " + postgresTableName + " ORDER BY version DESC")
if err != nil {
return versions, err
}
defer 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
}