Add Up command to create database and migrate

driver/driver.go

@@ -11,6 +11,7 @@ import (
 // Driver provides top level database functions
 type Driver interface {
 	Open(*url.URL) (*sql.DB, error)
+	DatabaseExists(*url.URL) (bool, error)
 	CreateDatabase(*url.URL) error
 	DropDatabase(*url.URL) error
 	CreateMigrationsTable(*sql.DB) error

driver/postgres/postgres.go

@@ -18,39 +18,66 @@ func (postgres Driver) Open(u *url.URL) (*sql.DB, error) {
 }
 
 // postgresExec runs a sql statement on the "postgres" database
-func (postgres Driver) postgresExec(u *url.URL, statement string) error {
+func (postgres Driver) openPostgresDB(u *url.URL) (*sql.DB, error) {
 	// connect to postgres database
 	postgresURL := *u
 	postgresURL.Path = "postgres"
 
-	db, err := postgres.Open(&postgresURL)
+	return postgres.Open(&postgresURL)
+}
+
+// CreateDatabase creates the specified database
+func (postgres Driver) CreateDatabase(u *url.URL) error {
+	name := shared.DatabaseName(u)
+	fmt.Printf("Creating: %s\n", name)
+
+	db, err := postgres.openPostgresDB(u)
 	if err != nil {
 		return err
 	}
 	defer db.Close()
 
-	// run statement
-	_, err = db.Exec(statement)
+	_, err = db.Exec(fmt.Sprintf("CREATE DATABASE %s",
+		pq.QuoteIdentifier(name)))
 
 	return err
 }
 
-// CreateDatabase creates the specified database
-func (postgres Driver) CreateDatabase(u *url.URL) error {
-	database := shared.DatabaseName(u)
-	fmt.Printf("Creating: %s\n", database)
-
-	return postgres.postgresExec(u, fmt.Sprintf("CREATE DATABASE %s",
-		pq.QuoteIdentifier(database)))
-}
-
 // DropDatabase drops the specified database (if it exists)
 func (postgres Driver) DropDatabase(u *url.URL) error {
-	database := shared.DatabaseName(u)
-	fmt.Printf("Dropping: %s\n", database)
+	name := shared.DatabaseName(u)
+	fmt.Printf("Dropping: %s\n", name)
 
-	return postgres.postgresExec(u, fmt.Sprintf("DROP DATABASE IF EXISTS %s",
-		pq.QuoteIdentifier(database)))
+	db, err := postgres.openPostgresDB(u)
+	if err != nil {
+		return err
+	}
+	defer db.Close()
+
+	_, err = db.Exec(fmt.Sprintf("DROP DATABASE IF EXISTS %s",
+		pq.QuoteIdentifier(name)))
+
+	return err
+}
+
+// DatabaseExists determines whether the database exists
+func (postgres Driver) DatabaseExists(u *url.URL) (bool, error) {
+	name := shared.DatabaseName(u)
+
+	db, err := postgres.openPostgresDB(u)
+	if err != nil {
+		return false, err
+	}
+	defer db.Close()
+
+	exists := false
+	err = db.QueryRow("SELECT true FROM pg_database WHERE datname = $1", name).
+		Scan(&exists)
+	if err == sql.ErrNoRows {
+		return false, nil
+	}
+
+	return exists, err
 }
 
 // HasMigrationsTable returns true if the schema_migrations table exists

driver/postgres/postgres_test.go

@@ -61,3 +61,36 @@ func TestCreateDropDatabase(t *testing.T) {
 		require.Equal(t, "pq: database \"dbmate\" does not exist", err.Error())
 	}()
 }
+
+func TestDatabaseExists(t *testing.T) {
+	d := postgres.Driver{}
+	u := testURL(t)
+
+	// drop any existing database
+	err := d.DropDatabase(u)
+	require.Nil(t, err)
+
+	// DatabaseExists should return false
+	exists, err := d.DatabaseExists(u)
+	require.Nil(t, err)
+	require.Equal(t, false, exists)
+
+	// create database
+	err = d.CreateDatabase(u)
+	require.Nil(t, err)
+
+	// DatabaseExists should return true
+	exists, err = d.DatabaseExists(u)
+	require.Nil(t, err)
+	require.Equal(t, true, exists)
+}
+
+func TestDatabaseExists_error(t *testing.T) {
+	d := postgres.Driver{}
+	u := testURL(t)
+	u.User = url.User("invalid")
+
+	exists, err := d.DatabaseExists(u)
+	require.Equal(t, "pq: role \"invalid\" does not exist", err.Error())
+	require.Equal(t, false, exists)
+}