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example_test.go
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example_test.go
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package pg_test
import (
"bytes"
"context"
"fmt"
"strings"
"sync"
"time"
"github.com/go-pg/pg/v10"
"github.com/go-pg/pg/v10/orm"
)
var (
ctx = context.Background()
pgdb *pg.DB
)
func init() {
pgdb = connect()
err := pgdb.Model((*Video)(nil)).DropTable(&orm.DropTableOptions{
IfExists: true,
Cascade: true,
})
panicIf(err)
err = pgdb.Model((*Video)(nil)).CreateTable(&orm.CreateTableOptions{})
panicIf(err)
}
func connect() *pg.DB {
return pg.Connect(pgOptions())
}
func panicIf(err error) {
if err != nil {
panic(err)
}
}
func ExampleConnect() {
db := pg.Connect(&pg.Options{
User: "postgres",
Password: "postgres",
Database: "postgres",
})
defer db.Close()
var n int
_, err := db.QueryOne(pg.Scan(&n), "SELECT 1")
panicIf(err)
fmt.Println(n)
// Output: 1
}
func ExampleDB_QueryOne() {
var user struct {
Name string
}
res, err := pgdb.QueryOne(&user, `
WITH users (name) AS (VALUES (?))
SELECT * FROM users
`, "admin")
panicIf(err)
fmt.Println(res.RowsAffected())
fmt.Println(user)
// Output: 1
// {admin}
}
func ExampleDB_QueryOne_returning_id() {
_, err := pgdb.Exec(`CREATE TEMP TABLE users(id serial, name varchar(500))`)
panicIf(err)
var user struct {
Id int32
Name string
}
user.Name = "admin"
_, err = pgdb.QueryOne(&user, `
INSERT INTO users (name) VALUES (?name) RETURNING id
`, &user)
panicIf(err)
fmt.Println(user)
// Output: {1 admin}
}
func ExampleDB_Exec() {
res, err := pgdb.Exec(`CREATE TEMP TABLE test()`)
panicIf(err)
fmt.Println(res.RowsAffected())
// Output: -1
}
func ExampleListener() {
ln := pgdb.Listen(ctx, "mychan")
defer ln.Close()
ch := ln.Channel()
go func() {
time.Sleep(time.Millisecond)
_, err := pgdb.Exec("NOTIFY mychan, ?", "hello world")
panicIf(err)
}()
notif := <-ch
fmt.Println(notif)
// Output: {mychan hello world}
}
func txExample() *pg.DB {
db := pg.Connect(&pg.Options{
User: "postgres",
Password: "postgres",
})
queries := []string{
`DROP TABLE IF EXISTS tx_test`,
`CREATE TABLE tx_test(counter int)`,
`INSERT INTO tx_test (counter) VALUES (0)`,
}
for _, q := range queries {
_, err := db.Exec(q)
panicIf(err)
}
return db
}
func ExampleDB_Begin() {
db := txExample()
incrInTx := func(db *pg.DB) error {
tx, err := db.Begin()
if err != nil {
return err
}
// Rollback tx on error.
defer tx.Rollback()
var counter int
_, err = tx.QueryOne(
pg.Scan(&counter), `SELECT counter FROM tx_test FOR UPDATE`)
if err != nil {
return err
}
counter++
_, err = tx.Exec(`UPDATE tx_test SET counter = ?`, counter)
if err != nil {
return err
}
return tx.Commit()
}
var wg sync.WaitGroup
for i := 0; i < 10; i++ {
wg.Add(1)
go func() {
defer wg.Done()
err := incrInTx(db)
panicIf(err)
}()
}
wg.Wait()
var counter int
_, err := db.QueryOne(pg.Scan(&counter), `SELECT counter FROM tx_test`)
panicIf(err)
fmt.Println(counter)
// Output: 10
}
func ExampleDB_RunInTransaction() {
db := txExample()
incrInTx := func(db *pg.DB) error {
// Transaction is automatically rolled back on error.
return db.RunInTransaction(ctx, func(tx *pg.Tx) error {
var counter int
_, err := tx.QueryOne(
pg.Scan(&counter), `SELECT counter FROM tx_test FOR UPDATE`)
if err != nil {
return err
}
counter++
_, err = tx.Exec(`UPDATE tx_test SET counter = ?`, counter)
return err
})
}
var wg sync.WaitGroup
for i := 0; i < 10; i++ {
wg.Add(1)
go func() {
defer wg.Done()
err := incrInTx(db)
panicIf(err)
}()
}
wg.Wait()
var counter int
_, err := db.QueryOne(pg.Scan(&counter), `SELECT counter FROM tx_test`)
panicIf(err)
fmt.Println(counter)
// Output: 10
}
func ExampleDB_Prepare() {
stmt, err := pgdb.Prepare(`SELECT $1::text, $2::text`)
panicIf(err)
var s1, s2 string
_, err = stmt.QueryOne(pg.Scan(&s1, &s2), "foo", "bar")
panicIf(err)
fmt.Println(s1, s2)
// Output: foo bar
}
func ExampleDB_Model_createTable() {
type Model1 struct {
Id int
}
type Model2 struct {
Id int
Name string
Model1Id int `pg:"on_delete:RESTRICT,on_update: CASCADE"`
Model1 *Model1 `pg:"rel:has-one"`
}
for _, model := range []interface{}{&Model1{}, &Model2{}} {
err := pgdb.Model(model).CreateTable(&orm.CreateTableOptions{
Temp: true, // create temp table
FKConstraints: true,
})
panicIf(err)
}
var info []struct {
ColumnName string
DataType string
}
_, err := pgdb.Query(&info, `
SELECT column_name, data_type
FROM information_schema.columns
WHERE table_name = 'model2'
`)
panicIf(err)
fmt.Println(info)
// Output: [{id bigint} {name text} {model1_id bigint}]
}
func ExampleInts() {
var nums pg.Ints
_, err := pgdb.Query(&nums, `SELECT generate_series(0, 10)`)
panicIf(err)
fmt.Println(nums)
// Output: [0 1 2 3 4 5 6 7 8 9 10]
}
func ExampleStrings() {
var strs pg.Strings
_, err := pgdb.Query(&strs, `
WITH users AS (VALUES ('foo'), ('bar')) SELECT * FROM users
`)
panicIf(err)
fmt.Println(strs)
// Output: [foo bar]
}
func ExampleDB_CopyFrom() {
_, err := pgdb.Exec(`CREATE TEMP TABLE words(word text, len int)`)
panicIf(err)
r := strings.NewReader("hello,5\nfoo,3\n")
_, err = pgdb.CopyFrom(r, `COPY words FROM STDIN WITH CSV`)
panicIf(err)
var buf bytes.Buffer
_, err = pgdb.CopyTo(&buf, `COPY words TO STDOUT WITH CSV`)
panicIf(err)
fmt.Println(buf.String())
// Output: hello,5
// foo,3
}
func ExampleDB_WithTimeout() {
var count int
// Use bigger timeout since this query is known to be slow.
_, err := pgdb.WithTimeout(time.Minute).QueryOne(pg.Scan(&count), `
SELECT count(*) FROM big_table
`)
panicIf(err)
}
func ExampleScan() {
var s1, s2 string
_, err := pgdb.QueryOne(pg.Scan(&s1, &s2), `SELECT ?, ?`, "foo", "bar")
panicIf(err)
fmt.Println(s1, s2)
// Output: foo bar
}
func ExampleError() {
video := &Video{
Id: 123,
}
_, err := pgdb.Model(video).Insert()
panicIf(err)
_, err = pgdb.Model(video).Insert()
if err != nil {
pgErr, ok := err.(pg.Error)
if ok && pgErr.IntegrityViolation() {
fmt.Println("video already exists:", err)
} else if pgErr.Field('S') == "PANIC" {
panic(err)
}
}
// Output: video already exists: ERROR #23505 duplicate key value violates unique constraint "videos_pkey"
}