8Ux60U9d

1package database
2
3import (
4	"context"
5	"fmt"
6	"github.com/jackc/pgx/v4"
7)
8
9type Migration struct {
10	Version   int
11	Sql       string
12	Arguments []interface{}
13}
14
15type Migrator struct {
16	migrations []*Migration
17	conn       *pgx.Conn
18	tableName  string
19}
20
21func CreateMigrator(conn *pgx.Conn) (*Migrator, error) {
22	migrator := &Migrator{
23		migrations: []*Migration{},
24		conn:       conn,
25		tableName:  "migrator",
26	}
27
28	err := migrator.CreateTable()
29	if err != nil {
30		return nil, err
31	}
32
33	return migrator, nil
34}
35
36func (migrator *Migrator) AddMigration(sql string, arguments ...interface{}) {
37	migration := &Migration{
38		Version:   len(migrator.migrations) + 1,
39		Sql:       sql,
40		Arguments: arguments,
41	}
42
43	migrator.migrations = append(migrator.migrations, migration)
44}
45
46func (migrator *Migrator) Run() error {
47	lastVersion, err := migrator.getLastVersion()
48	if err != nil {
49		return err
50	}
51
52	for _, migration := range migrator.migrations {
53		if migration.Version > lastVersion {
54			err = migrator.execute(migration)
55			if err != nil {
56				return err
57			}
58		}
59	}
60
61	return nil
62}
63
64func (migrator *Migrator) getLastVersion() (int, error) {
65	var version int
66	err := migrator.conn.QueryRow(context.Background(), fmt.Sprintf("select max(version) version from %s", migrator.tableName)).Scan(&version)
67	if err != nil {
68		return 0, err
69	}
70
71	return version, nil
72}
73
74func (migrator *Migrator) execute(migration *Migration) error {
75	_, err := migrator.conn.Exec(context.Background(), migration.Sql, migration.Arguments...)
76	if err != nil {
77		return err
78	}
79
80	_, err = migrator.conn.Exec(context.Background(), fmt.Sprintf(`
81	insert into %s (version)
82	values (%d)`, migrator.tableName, migration.Version), migration.Arguments...)
83	if err != nil {
84		return err
85	}
86
87	return nil
88}
89
90func (migrator *Migrator) CreateTable() error {
91	_, err := migrator.conn.Exec(context.Background(), fmt.Sprintf(`
92	create table if not exists %s
93	(
94		version int constraint migrator_pk primary key
95	);
96	`, migrator.tableName))
97	if err != nil {
98		return err
99	}
100
101	return nil
102}