How to create something in PostgreSQL Database

Question

I'm learning to use PostgreSQL and GORM. I'm creating a struct, connecting to database, and trying to write in to database.

Source code:

db, err := gorm.Open("postgres","user=superuser password=ojcafizp123 dbname=gorm sslmode=disable")
    if err != nil {
        panic(err.Error())
    }
    defer db.Close()

    database := db.DB()

    err = database.Ping()

    if err != nil {
        panic(err.Error())
    }

    fmt.Println("Connection to PostgreSQL was successful!")

    port := ":3000"
    r := chi.NewRouter()
    r.Get("/api/test",Test)
    http.ListenAndServe(port, r)
}



func CreateRate (w http.ResponseWriter, r *http.Request) {
    db, err := gorm.Open("postgres","user=superuser password=ojcafizp123 dbname=gorm sslmode=disable")
    cure := Crypto{"BTC","USD",10000,100}
    if db.NewRecord(cure) {
        err = db.Create(&cure).Error
        if err != nil{
            panic(err.Error())

        }
    }
}

Struct:

type Crypto struct {
    Cur1 string `json:"cur1"`
    Cur2 string `json:"cur2"`
    Rate float64 `json:"rate"`
    Timestamp int64 `json:"timestamp"`
}

Trying to find my record in the database:

func Test (w http.ResponseWriter, r *http.Request) {
    db, err := gorm.Open("postgres","user=superuser password=ojcafizp123 dbname=gorm sslmode=disable")
    var testcur Crypto
    db.First(&testcur)
    fmt.Println(testcur)
    if err != nil {
        fmt.Println("No testcur detected")
    }

}

But got this:

Connection to PostgreSQL was successful! { 0 0}

(/home/superuser/go/src/CryptoProject/main.go:97) [2019-07-27 05:09:10] pq: relation "cryptos" does not exist

The connection is working, but the base is still empty.

Just to add to @khampson's answer, you are nowhere actually calling `CreateRate`, so even if you create the table, without first inserting something into it the `Test` would still fail. And one more thing, the way you handle errors in your `Test` handler is just wrong, first you're ignoring the error returned from `Open`, and then, when you call `First`, instead of checking if that produced an error you check the one returned from `Open`. — mkopriva, Jul 27 '19 at 04:05

score 2 · Answer 1 · answered Jul 27 '19 at 03:01

The error is saying that the table cryptos does not currently exist, which is why the insert is not working and there's nothing in the database.

I have not previously used GORM specifically, but if it's similar to other ORMs, you would need to create a data model representing the table, and then it could create the table using that model. A quick scan of its doc shows GORM has a function called CreateTable that can be called against a Model.

You could also create the table outside of GORM using regular SQL via a tool such as psql.

To expand on this: [using any ORM for database change management is a Very Bad Idea™](https://stackoverflow.com/a/22572463/1296707). — Markus W Mahlberg, Jul 27 '19 at 10:30

score 0 · Answer 2 · answered Jul 28 '19 at 15:09

0

Addition to @khampson, you can use AutoMigrate feature:

type Product struct {
  gorm.Model
  Code string
  Price uint
}

// Migrate the schema
db.AutoMigrate(&Product{})

Full example.

answered Jul 28 '19 at 15:09

ceth

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How to create something in PostgreSQL Database

2 Answers2