101 lines
2.2 KiB
Go
101 lines
2.2 KiB
Go
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package migrate
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import (
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"database/sql"
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"fmt"
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"time"
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)
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const table = "dbversion"
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var tableCreateSql = "CREATE TABLE " + table + ` (
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id INTEGER PRIMARY KEY AUTOINCREMENT,
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description VARCHAR,
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applied TIMESTAMP
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);`
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var tableCheckSql = "SELECT * FROM " + table + ";"
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var versionCheckSql = "SELECT id FROM " + table + " ORDER BY id DESC LIMIT 0, 1;"
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var versionInsertSql = "INSERT INTO " + table + "(description, applied) VALUES (?,?);"
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type Error struct {
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description string
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wrapped error
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}
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func (e Error) Error() string {
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return fmt.Sprintf("%s: %v", e.description, e.wrapped)
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}
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func (e Error) Unwrap() error {
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return e.wrapped
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}
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type Record struct {
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Description string
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F func(ctx Context) error
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}
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type Context interface {
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Exec(query string, args ...interface{}) (sql.Result, error)
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Query(query string, args ...interface{}) (*sql.Rows, error)
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}
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func Apply(ctx Context, migrations []Record) (err error) {
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if err = initialize(ctx); err == nil {
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var currentVersion int64
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if currentVersion, err = dbVersion(ctx); err == nil {
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migrations = migrations[currentVersion:] // only apply what hasnt been been applied already
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for i, m := range migrations {
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if err = apply(ctx, m); err != nil {
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err = Error{
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description: fmt.Sprintf("error performing migration \"%s\"", migrations[i].Description),
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wrapped: err,
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}
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break
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}
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}
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}
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}
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return
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}
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func initialize(ctx Context) (err error) {
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if noVersionTable(ctx) {
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return createVersionTable(ctx)
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}
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return nil
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}
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func noVersionTable(ctx Context) bool {
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rows, table_check := ctx.Query(tableCheckSql)
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if rows != nil {
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defer rows.Close()
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}
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return table_check != nil
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}
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func apply(ctx Context, r Record) (err error) {
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if err = r.F(ctx); err == nil {
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err = incrementVersion(ctx, r.Description)
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}
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return
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}
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func createVersionTable(ctx Context) (err error) {
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_, err = ctx.Exec(tableCreateSql)
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return
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}
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func incrementVersion(ctx Context, description string) (err error) {
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_, err = ctx.Exec(versionInsertSql, description, time.Now())
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return
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}
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func dbVersion(ctx Context) (id int64, err error) {
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row, err := ctx.Query(versionCheckSql)
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if row.Next() {
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err = row.Scan(&id)
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}
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return
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}
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