Mainflux.mainflux/vendor/github.com/go-pg/pg/v9

PostgreSQL client and ORM for Golang

Features

• Basic types: integers, floats, string, bool, time.Time, net.IP, net.IPNet.
• sql.NullBool, sql.NullString, sql.NullInt64, sql.NullFloat64 and pg.NullTime.
• sql.Scanner and sql/driver.Valuer interfaces.
• Structs, maps and arrays are marshalled as JSON by default.
• PostgreSQL multidimensional Arrays using array tag and Array wrapper.
• Hstore using hstore tag and Hstore wrapper.
• Composite types.
• All struct fields are nullable by default and zero values (empty string, 0, zero time, empty map or slice, nil ptr) are marshalled as SQL NULL. pg:",notnull" is used to add SQL NOT NULL constraint and pg:",use_zero" to allow Go zero values.
• Transactions.
• Prepared statements.
• Notifications using LISTEN and NOTIFY.
• Copying data using COPY FROM and COPY TO.
• Timeouts and canceling queries using context.Context.
• Automatic connection pooling with circuit breaker support.
• Queries retries on network errors.
• Working with models using ORM and SQL.
• Scanning variables using ORM and SQL.
• SelectOrInsert using on-conflict.
• INSERT ... ON CONFLICT DO UPDATE using ORM.
• Bulk/batch inserts, updates, and deletes.
• Common table expressions using WITH and WrapWith.
• CountEstimate using EXPLAIN to get estimated number of matching rows.
• ORM supports has one, belongs to, has many, and many to many with composite/multi-column primary keys.
• Soft deletes.
• Creating tables from structs.
• ForEach that calls a function for each row returned by the query without loading all rows into the memory.
• Works with PgBouncer in transaction pooling mode.

Ecosystem

• Migrations by vmihailenco and robinjoseph08.
• Sharding.
• Model generator from SQL tables.
• urlstruct to decode url.Values into structs.

Get Started

go-pg requires a Go version with Modules support and uses import versioning. So please make sure to initialize a Go module before installing go-pg:

go mod init github.com/my/repo
go get github.com/go-pg/pg/v9

• Wiki
• API docs
• Examples

Look & Feel

package pg_test

import (
    "fmt"

    "github.com/go-pg/pg/v9"
    "github.com/go-pg/pg/v9/orm"
)

type User struct {
    Id     int64
    Name   string
    Emails []string
}

func (u User) String() string {
    return fmt.Sprintf("User<%d %s %v>", u.Id, u.Name, u.Emails)
}

type Story struct {
    Id       int64
    Title    string
    AuthorId int64
    Author   *User
}

func (s Story) String() string {
    return fmt.Sprintf("Story<%d %s %s>", s.Id, s.Title, s.Author)
}

func ExampleDB_Model() {
    db := pg.Connect(&pg.Options{
        User: "postgres",
    })
    defer db.Close()

    err := createSchema(db)
    if err != nil {
        panic(err)
    }

    user1 := &User{
        Name:   "admin",
        Emails: []string{"admin1@admin", "admin2@admin"},
    }
    err = db.Insert(user1)
    if err != nil {
        panic(err)
    }

    err = db.Insert(&User{
        Name:   "root",
        Emails: []string{"root1@root", "root2@root"},
    })
    if err != nil {
        panic(err)
    }

    story1 := &Story{
        Title:    "Cool story",
        AuthorId: user1.Id,
    }
    err = db.Insert(story1)
    if err != nil {
        panic(err)
    }

    // Select user by primary key.
    user := &User{Id: user1.Id}
    err = db.Select(user)
    if err != nil {
        panic(err)
    }

    // Select all users.
    var users []User
    err = db.Model(&users).Select()
    if err != nil {
        panic(err)
    }

    // Select story and associated author in one query.
    story := new(Story)
    err = db.Model(story).
        Relation("Author").
        Where("story.id = ?", story1.Id).
        Select()
    if err != nil {
        panic(err)
    }

    fmt.Println(user)
    fmt.Println(users)
    fmt.Println(story)
    // Output: User<1 admin [admin1@admin admin2@admin]>
    // [User<1 admin [admin1@admin admin2@admin]> User<2 root [root1@root root2@root]>]
    // Story<1 Cool story User<1 admin [admin1@admin admin2@admin]>>
}

func createSchema(db *pg.DB) error {
    for _, model := range []interface{}{(*User)(nil), (*Story)(nil)} {
        err := db.CreateTable(model, &orm.CreateTableOptions{
            Temp: true,
        })
        if err != nil {
            return err
        }
    }
    return nil
}

See also

• Golang msgpack
• Golang message task queue