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migrate.go
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/
migrate.go
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package migrations
import (
"context"
"database/sql"
"embed"
"errors"
"io/fs"
"os"
"github.com/golang-migrate/migrate/v4"
"github.com/golang-migrate/migrate/v4/database/postgres"
"github.com/golang-migrate/migrate/v4/source"
"github.com/golang-migrate/migrate/v4/source/iofs"
"golang.org/x/xerrors"
)
//go:embed *.sql
var migrations embed.FS
func setup(db *sql.DB) (source.Driver, *migrate.Migrate, error) {
ctx := context.Background()
sourceDriver, err := iofs.New(migrations, ".")
if err != nil {
return nil, nil, xerrors.Errorf("create iofs: %w", err)
}
// migration_cursor is a v1 migration table. If this exists, we're on v1.
// Do no run v2 migrations on a v1 database!
row := db.QueryRowContext(ctx, "SELECT * FROM migration_cursor;")
if row.Err() == nil {
return nil, nil, xerrors.Errorf("currently connected to a Coder v1 database, aborting database setup")
}
// there is a postgres.WithInstance() method that takes the DB instance,
// but, when you close the resulting Migrate, it closes the DB, which
// we don't want. Instead, create just a connection that will get closed
// when migration is done.
conn, err := db.Conn(ctx)
if err != nil {
return nil, nil, xerrors.Errorf("postgres connection: %w", err)
}
dbDriver, err := postgres.WithConnection(ctx, conn, &postgres.Config{})
if err != nil {
return nil, nil, xerrors.Errorf("wrap postgres connection: %w", err)
}
m, err := migrate.NewWithInstance("", sourceDriver, "", dbDriver)
if err != nil {
return nil, nil, xerrors.Errorf("new migrate instance: %w", err)
}
return sourceDriver, m, nil
}
// Up runs SQL migrations to ensure the database schema is up-to-date.
func Up(db *sql.DB) (retErr error) {
_, m, err := setup(db)
if err != nil {
return xerrors.Errorf("migrate setup: %w", err)
}
defer func() {
srcErr, dbErr := m.Close()
if retErr != nil {
return
}
if dbErr != nil {
retErr = dbErr
return
}
retErr = srcErr
}()
err = m.Up()
if err != nil {
if errors.Is(err, migrate.ErrNoChange) {
// It's OK if no changes happened!
return nil
}
return xerrors.Errorf("up: %w", err)
}
return nil
}
// Down runs all down SQL migrations.
func Down(db *sql.DB) error {
_, m, err := setup(db)
if err != nil {
return xerrors.Errorf("migrate setup: %w", err)
}
err = m.Down()
if err != nil {
if errors.Is(err, migrate.ErrNoChange) {
// It's OK if no changes happened!
return nil
}
return xerrors.Errorf("down: %w", err)
}
return nil
}
// EnsureClean checks whether all migrations for the current version have been
// applied, without making any changes to the database. If not, returns a
// non-nil error.
func EnsureClean(db *sql.DB) error {
sourceDriver, m, err := setup(db)
if err != nil {
return xerrors.Errorf("migrate setup: %w", err)
}
version, dirty, err := m.Version()
if err != nil {
return xerrors.Errorf("get migration version: %w", err)
}
if dirty {
return xerrors.Errorf("database has not been cleanly migrated")
}
// Verify that the database's migration version is "current" by checking
// that a migration with that version exists, but there is no next version.
err = CheckLatestVersion(sourceDriver, version)
if err != nil {
return xerrors.Errorf("database needs migration: %w", err)
}
return nil
}
// Returns nil if currentVersion corresponds to the latest available migration,
// otherwise an error explaining why not.
func CheckLatestVersion(sourceDriver source.Driver, currentVersion uint) error {
// This is ugly, but seems like the only way to do it with the public
// interfaces provided by golang-migrate.
// Check that there is no later version
nextVersion, err := sourceDriver.Next(currentVersion)
if err == nil {
return xerrors.Errorf("current version is %d, but later version %d exists", currentVersion, nextVersion)
}
if !errors.Is(err, os.ErrNotExist) {
return xerrors.Errorf("get next migration after %d: %w", currentVersion, err)
}
// Once we reach this point, we know that either currentVersion doesn't
// exist, or it has no successor (the return value from
// sourceDriver.Next() is the same in either case). So we need to check
// that either it's the first version, or it has a predecessor.
firstVersion, err := sourceDriver.First()
if err != nil {
// the total number of migrations should be non-zero, so this must be
// an actual error, not just a missing file
return xerrors.Errorf("get first migration: %w", err)
}
if firstVersion == currentVersion {
return nil
}
_, err = sourceDriver.Prev(currentVersion)
if err != nil {
return xerrors.Errorf("get previous migration: %w", err)
}
return nil
}
// Stepper returns a function that runs SQL migrations one step at a time.
//
// Stepper cannot be closed pre-emptively, it must be run to completion
// (or until an error is encountered).
func Stepper(db *sql.DB) (next func() (version uint, more bool, err error), err error) {
_, m, err := setup(db)
if err != nil {
return nil, xerrors.Errorf("migrate setup: %w", err)
}
return func() (version uint, more bool, err error) {
defer func() {
if !more {
srcErr, dbErr := m.Close()
if err != nil {
return
}
if dbErr != nil {
err = dbErr
return
}
err = srcErr
}
}()
err = m.Steps(1)
if err != nil {
switch {
case errors.Is(err, migrate.ErrNoChange):
// It's OK if no changes happened!
return 0, false, nil
case errors.Is(err, fs.ErrNotExist):
// This error is encountered at the of Steps when
// reading from embed.FS.
return 0, false, nil
}
return 0, false, xerrors.Errorf("Step: %w", err)
}
v, _, err := m.Version()
if err != nil {
return 0, false, err
}
return v, true, nil
}, nil
}