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|
package migrate
import (
"database/sql"
"fmt"
"sort"
"time"
)
const (
// NilVersion is a Claytons version
// "the version you are at when you are not at a version"
NilVersion = -1
)
// Migration interface
type Migration interface {
// The version of this migration
Version() int64
// Run the migration
Run(*sql.Tx) error
}
// ResultFunc is the callback signature
type ResultFunc func(int64, int64, error)
// A Migrator collates and runs migrations
type Migrator struct {
db *sql.DB
migrations []Migration
versionTable *string
stmts map[string]*sql.Stmt
prepared bool
callback ResultFunc
}
// Sort those migrations
type sorted []Migration
func (s sorted) Len() int { return len(s) }
func (s sorted) Less(i, j int) bool { return s[i].Version() < s[j].Version() }
func (s sorted) Swap(i, j int) { s[i], s[j] = s[j], s[i] }
// Version reports the current version of the database
func (m *Migrator) Version() (int64, error) {
err := m.prepareForMigration()
if err != nil {
return NilVersion, err
}
var version int64
err = m.stmts["getVersion"].QueryRow().Scan(&version)
if err != nil {
if err == sql.ErrNoRows {
return NilVersion, nil
}
return NilVersion, err
}
return version, nil
}
// Migrate migrates the database to the highest possible version
func (m *Migrator) Migrate() error {
err := m.prepareForMigration()
if err != nil {
return err
}
// Get the last available migration
v := m.migrations[len(m.migrations)-1].Version()
return m.MigrateTo(v)
}
// MigrateTo migrates the database to the specified version
func (m *Migrator) MigrateTo(toVersion int64) error {
err := m.prepareForMigration()
if err != nil {
return err
}
maxVersion := m.migrations[len(m.migrations)-1].Version()
currVersion, err := m.Version()
if err != nil {
return err
}
if currVersion >= toVersion {
go m.callback(maxVersion, currVersion, nil)
return nil
}
for _, mig := range m.migrations {
nextVersion := mig.Version()
// Skip old migrations
if nextVersion <= currVersion {
continue
}
// Ensure contiguous
if currVersion != NilVersion && nextVersion != currVersion+1 {
return fmt.Errorf("non-contiguous migration: %v -> %v", currVersion, nextVersion)
}
if currVersion < nextVersion && nextVersion <= toVersion {
// Scope for defer
err = func() error {
// Start a transaction
tx, err := m.db.Begin()
if err != nil {
return fmt.Errorf("migration %d failed: %s", nextVersion, err)
}
defer tx.Commit()
// Run the migration
if err = mig.Run(tx); err != nil {
tx.Rollback()
return fmt.Errorf("migration %d failed: %s", nextVersion, err)
}
// Update the version entry
if err = m.setVersion(tx, nextVersion); err != nil {
tx.Rollback()
return fmt.Errorf("migration %d failed: %s", nextVersion, err)
}
return tx.Commit()
}()
if m.callback != nil {
go m.callback(maxVersion, nextVersion, err)
}
if err != nil {
return err
}
}
currVersion = nextVersion
}
return nil
}
func (m *Migrator) setVersion(tx *sql.Tx, version int64) (err error) {
if version >= 0 {
_, err = tx.Stmt(m.stmts["insertVersion"]).Exec(version, time.Now().Unix())
}
return err
}
func (m *Migrator) prepareForMigration() error {
if m.prepared {
return nil
}
if m.versionTable == nil {
vt := "schema_version"
m.versionTable = &vt
}
if _, err := m.db.Exec(fmt.Sprintf(createTableSQL, *m.versionTable)); err != nil {
return err
}
if err := m.prepareStmts(); err != nil {
return err
}
sort.Sort(sorted(m.migrations))
m.prepared = true
return nil
}
func (m *Migrator) prepareStmts() error {
m.stmts = make(map[string]*sql.Stmt)
s, err := m.db.Prepare(fmt.Sprintf(getVersionSQL, NilVersion, *m.versionTable))
if err != nil {
return err
}
m.stmts["getVersion"] = s
s, err = m.db.Prepare(fmt.Sprintf(insertVersionSQL, *m.versionTable))
if err != nil {
return err
}
m.stmts["insertVersion"] = s
return nil
}
const (
getVersionSQL = `select coalesce(max(version), %d) from %s`
insertVersionSQL = `insert into %s (version, applied) values ($1, $2)`
// Use Unix timestamp for time so it works for SQLite and PostgreSQL
createTableSQL = `create table if not exists %s (
version bigint not null primary key,
applied int)`
)
|
