93 lines
2.1 KiB
Go
93 lines
2.1 KiB
Go
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// Package migrate allows you to update your database from your application
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package migrate
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import (
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"database/sql"
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"errors"
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"fmt"
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"strconv"
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)
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// Options contains all settings
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type Options struct {
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TableName string // Name used for version info table; defaults to DefaultTableName if not set
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Schema string // Schema used for version info table; For PostgreSQL, ignored if not set
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AssetPrefix string
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}
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// DefaultTableName is the name used when no TableName is specified in Options
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const DefaultTableName = `version`
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// ErrUpdatesMissing indicates an update is missing, making it impossible to execute the migration
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var ErrUpdatesMissing = errors.New(`Missing migration files`)
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// ErrDatabaseNewer indicates that the database version is newer than the requested version. We throw an error because downgrades might cause dataloss
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var ErrDatabaseNewer = errors.New(`Current version is newer than the requested version`)
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const fileFormat = `%04d.sql`
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// AssetFunc is a function that returns the data for the given name
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type AssetFunc func(string) ([]byte, error)
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// Migrate executes
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func Migrate(db *sql.DB, version int, o Options, asset AssetFunc) error {
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if o.TableName == `` {
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o.TableName = DefaultTableName
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}
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table := o.TableName
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if o.Schema != `` {
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table = o.Schema + `.` + table
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}
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_, err := db.Exec(`CREATE TABLE IF NOT EXISTS ` + table + ` (Version integer NOT NULL PRIMARY KEY)`)
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if err != nil {
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return err
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}
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row := db.QueryRow(`SELECT Version FROM ` + table + ` ORDER BY Version DESC`)
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if err != nil {
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return err
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}
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var v int
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err = row.Scan(&v)
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if err != sql.ErrNoRows && err != nil {
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return err
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}
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if v > version {
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return ErrDatabaseNewer
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}
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tx, err := db.Begin()
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if err != nil {
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return err
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}
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defer tx.Rollback()
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for i := v + 1; i <= version; i++ {
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asset, err := asset(fmt.Sprintf(o.AssetPrefix+fileFormat, version))
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if err != nil {
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return ErrUpdatesMissing
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}
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_, err = tx.Exec(string(asset))
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if err != nil {
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return err
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}
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_, err = tx.Exec(`INSERT INTO ` + table + ` VALUES (` + strconv.Itoa(i) + `)`)
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if err != nil {
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return err
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}
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}
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err = tx.Commit()
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if err != nil {
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return err
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}
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return nil
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}
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