pg

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 Go to latest Published: Dec 13, 2016 License: BSD-2-Clause Imports: 19 Imported by: 0

README

PostgreSQL client for Golang Build Status

Supports:

API docs: http://godoc.org/gopkg.in/pg.v5. Examples: http://godoc.org/gopkg.in/pg.v5#pkg-examples.

Table of contents

Installation

Install:

go get gopkg.in/pg.v5

Quickstart

package pg_test

import (
	"fmt"

	"gopkg.in/pg.v5"
)

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 createSchema(db *pg.DB) error {
	queries := []string{
		`CREATE TEMP TABLE users (id serial, name text, emails jsonb)`,
		`CREATE TEMP TABLE stories (id serial, title text, author_id bigint)`,
	}
	for _, q := range queries {
		_, err := db.Exec(q)
		if err != nil {
			return err
		}
	}
	return nil
}

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

	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.
	var story Story
	err = db.Model(&story).
		Column("story.*", "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]>>
}

Model definition

Models are defined using Go structs which are mapped to PostgreSQL tables. Exported struct fields are mapped to table columns. Table name and alias are automatically derived from struct name by underscoring it; table name is also pluralized (struct Genre -> table genres AS genre). Default table name can be overrided using tableName field. Column name is derived from struct field name by underscoring it (field ParentId -> column parent_id). Default column name can be overrided using sql tag. Order of struct fields does not matter with the only exception being primary keys that must be defined before any other fields. Otherwise table relationships can be recognized incorrectly.

Please note that most struct tags in the following example have the same values as the defaults and are included only for demonstration purposes.

type Genre struct {
	// tableName is an optional field that specifies custom table name and alias.
	// By default go-pg generates table name and alias from struct name.
	tableName struct{} `sql:"genres,alias:genre"` // default values are the same

	Id     int // Id is automatically detected as primary key
	Name   string
	Rating int `sql:"-"` // - is used to ignore field

	Books []Book `pg:",many2many:book_genres"` // many to many relation

	ParentId  int
	Subgenres []Genre `pg:",fk:Parent"` // fk specifies prefix for foreign key (ParentId)
}

func (g Genre) String() string {
	return fmt.Sprintf("Genre<Id=%d Name=%q>", g.Id, g.Name)
}

type Author struct {
	ID    int // both "Id" and "ID" are detected as primary key
	Name  string
	Books []*Book // has many relation
}

func (a Author) String() string {
	return fmt.Sprintf("Author<ID=%d Name=%q>", a.ID, a.Name)
}

type BookGenre struct {
	tableName struct{} `sql:",alias:bg"` // custom table alias

	BookId  int `sql:",pk"` // pk tag is used to mark field as primary key
	GenreId int `sql:",pk"`

	Genre_Rating int // belongs to and is copied to Genre model
}

type Book struct {
	Id        int
	Title     string
	AuthorID  int
	Author    *Author // has one relation
	EditorID  int
	Editor    *Author // has one relation
	CreatedAt time.Time

	Genres       []Genre       `pg:",many2many:book_genres" gorm:"many2many:book_genres;"` // many to many relation
	Translations []Translation // has many relation
	Comments     []Comment     `pg:",polymorphic:Trackable"` // has many polymorphic relation
}

func (b Book) String() string {
	return fmt.Sprintf("Book<Id=%d Title=%q>", b.Id, b.Title)
}

func (b *Book) BeforeInsert(db orm.DB) error {
	if b.CreatedAt.IsZero() {
		b.CreatedAt = time.Now()
	}
	return nil
}

// BookWithCommentCount is like Book model, but has additional CommentCount
// field that is used to select data into it. The use of `pg:",override"` tag
// is essential here and it overrides internal model properties such as table name.
type BookWithCommentCount struct {
	Book `pg:",override"`

	CommentCount int
}

type Translation struct {
	tableName struct{} `sql:",alias:tr"` // custom table alias

	Id     int
	BookId int
	Book   *Book // belongs to relation
	Lang   string

	Comments []Comment `pg:",polymorphic:Trackable"` // has many polymorphic relation
}

type Comment struct {
	TrackableId   int    // Book.Id or Translation.Id
	TrackableType string // "Book" or "Translation"
	Text          string
}

Model hooks

Models support optional hooks that accept orm.DB interface which value can be either *pg.DB or *pg.Tx.

// AfterQuery is called after the model is loaded from database.
func (b *Book) AfterQuery(db orm.DB) error {
    return updateBookCache(b)
}

// AfterSelect is called after the model and all its relations (e.g. has one)
// are loaded from database.
func (b *Book) AfterSelect(db orm.DB) error {
    return updateBookCache(b)
}

func (b *Book) BeforeInsert(db orm.DB) error {
    if b.CreatedAt.IsZero() {
        b.CreatedAt = time.Now()
    }
    return nil
}

func (b *Book) AfterInsert(db orm.DB) error {
    return updateBookCache(b)
}

func (b *Book) BeforeUpdate(db orm.DB) error {
   return nil
}

func (b *Book) AfterUpdate(db orm.DB) error {
   return nil
}

func (b *Book) BeforeDelete(db orm.DB) error {
   return nil
}

func (b *Book) AfterDelete(db orm.DB) error {
   return nil
}

Writing queries

Placeholders
package pg_test

import (
	"fmt"

	"gopkg.in/pg.v5"
)

type Params struct {
	X int
	Y int
}

func (p *Params) Sum() int {
	return p.X + p.Y
}

// go-pg recognizes placeholders (`?`) in queries and replaces them
// with parameters when queries are executed. Parameters are escaped
// before replacing according to PostgreSQL rules. Specifically:
//   - all parameters are properly quoted against SQL injections;
//   - null byte is removed;
//   - JSON/JSONB gets `\u0000` escaped as `\\u0000`.
func Example_placeholders() {
	var num int

	// Simple params.
	_, err := db.Query(pg.Scan(&num), "SELECT ?", 42)
	if err != nil {
		panic(err)
	}
	fmt.Println("simple:", num)

	// Indexed params.
	_, err = db.Query(pg.Scan(&num), "SELECT ?0 + ?0", 1)
	if err != nil {
		panic(err)
	}
	fmt.Println("indexed:", num)

	// Named params.
	params := &Params{
		X: 1,
		Y: 1,
	}
	_, err = db.Query(pg.Scan(&num), "SELECT ?x + ?y + ?Sum", &params)
	if err != nil {
		panic(err)
	}
	fmt.Println("named:", num)

	// Global params.
	_, err = db.WithParam("z", 1).Query(pg.Scan(&num), "SELECT ?x + ?y + ?z", &params)
	if err != nil {
		panic(err)
	}
	fmt.Println("global:", num)

	// Output: simple: 42
	// indexed: 2
	// named: 4
	// global: 3
}
Select
// Select book by primary key.
err := db.Select(&book)
// SELECT "book"."id", "book"."title", "book"."text"
// FROM "books" WHERE id = 1

// Select only book title and text.
err := db.Model(&book).Column("title", "text").Where("id = ?", 1).Select()
// SELECT "title", "text"
// FROM "books" WHERE id = 1

// Select only book title and text into variables.
var title, text string
err := db.Model(&Book{}).Column("title", "text").Where("id = ?", 1).Select(&title, &text)
// SELECT "title", "text"
// FROM "books" WHERE id = 1

// Select book using WHERE.
err := db.Model(&book).
    Where("id > ?", 100).
    Where("title LIKE ?", "my%").
    Limit(1).
    Select()
// SELECT "book"."id", "book"."title", "book"."text"
// FROM "books"
// WHERE (id > 100) AND (title LIKE 'my%')
// LIMIT 1

// Select first 20 books.
err := db.Model(&books).Order("id ASC").Limit(20).Select()
// SELECT "book"."id", "book"."title", "book"."text"
// FROM "books"
// ORDER BY id ASC LIMIT 20

// Count books.
count, err := db.Model(&Book{}).Count()
// SELECT count(*) FROM "books"

// Select 20 books and count all books.
count, err := db.Model(&books).Limit(20).SelectAndCount()
// SELECT "book"."id", "book"."title", "book"."text"
// FROM "books" LIMIT 20
//
// SELECT count(*) FROM "books"

// Select 20 books and count estimated number of books.
count, err := db.Model(&books).Limit(20).SelectAndCountEstimate(100000)
// SELECT "book"."id", "book"."title", "book"."text"
// FROM "books" LIMIT 20
//
// EXPLAIN SELECT 2147483647 FROM "books"
// SELECT count(*) FROM "books"

// Select author id and number of books.
var res []struct {
    AuthorId  int
    BookCount int
}
err := db.Model(&Book{}).
    Column("author_id").
    ColumnExpr("count(*) AS book_count").
    Group("author_id").
    Order("book_count DESC").
    Select(&res)
// SELECT "author_id", count(*) AS book_count
// FROM "books" AS "book"
// GROUP BY author_id
// ORDER BY book_count DESC

// Select book ids as PostgreSQL array.
var ids []int
err := db.Model(&Book{}).ColumnExpr("array_agg(id)").Select(pg.Array(&ids))
// SELECT array_agg(id) FROM "books"

// Select books using WITH statement.
authorBooks := db.Model(&Book{}).Where("author_id = ?", 1)
err := db.Model(nil).
    With("author_books", authorBooks).
    Table("author_books").
    Select(&books)
// WITH "author_books" AS (
//   SELECT "book"."id", "book"."title", "book"."text"
//   FROM "books" AS "book" WHERE (author_id = 1)
// )
// SELECT * FROM "author_books"

// Same query using WrapWith.
err := db.Model(&books).
    Where("author_id = ?", 1).
    WrapWith("author_books").
    Table("author_books").
    Select(&books)
// WITH "author_books" AS (
//   SELECT "book"."id", "book"."title", "book"."text"
//   FROM "books" AS "book" WHERE (author_id = 1)
// )
// SELECT * FROM "author_books"
Column names
// Select book and associated author.
err := db.Model(&book).Column("Author").Select()
// SELECT
//   "book"."id", "book"."title", "book"."text",
//   "author"."id" AS "author__id", "author"."name" AS "author__name"
// FROM "books"
// LEFT JOIN "users" AS "author" ON "author"."id" = "book"."author_id"
// WHERE id = 1

// Select book id and associated author id.
err := db.Model(&book).Column("book.id", "Author.id").Select()
// SELECT "book"."id", "author"."id" AS "author__id"
// FROM "books"
// LEFT JOIN "users" AS "author" ON "author"."id" = "book"."author_id"
// WHERE id = 1

// Select book and join author without selecting it.
err := db.Model(&book).Column("Author._").Select()
// SELECT "book"."id"
// FROM "books"
// LEFT JOIN "users" AS "author" ON "author"."id" = "book"."author_id"
// WHERE id = 1

// Join and select book author without selecting book.
err := db.Model(&book).Column("_", "Author").Select()
// SELECT "author"."id" AS "author__id", "author"."name" AS "author__name"
// FROM "books"
// LEFT JOIN "users" AS "author" ON "author"."id" = "book"."author_id"
// WHERE id = 1
Reusing queries
// Pager sets LIMIT and OFFSET from the URL values:
//   - ?limit=10 - sets q.Limit(10), max limit is 1000.
//   - ?page=5 - sets q.Offset((page - 1) * limit), max offset is 1000000.
func Pager(urlValues url.Values, defaultLimit int) func(*Query) (*Query, error) {
	return func(q *Query) (*Query, error) {
		const maxLimit = 1000
		const maxOffset = 1e6

		limit, err := intParam(urlValues, "limit")
		if err != nil {
			return nil, err
		}
		if limit < 1 {
			limit = defaultLimit
		} else if limit > maxLimit {
			return nil, fmt.Errorf("limit can't bigger than %d", maxLimit)
		}
		if limit > 0 {
			q = q.Limit(limit)
		}

		page, err := intParam(urlValues, "page")
		if err != nil {
			return nil, err
		}
		if page > 0 {
			offset := (page - 1) * limit
			if offset > maxOffset {
				return nil, fmt.Errorf("offset can't bigger than %d", maxOffset)
			}
			q = q.Offset(offset)
		}

		return q, nil
	}
}

var books []Book
err := db.Model(&books).Apply(orm.Pager(req.URL.Query())).Select()
// SELECT * FROM "books" LIMIT 20
Insert
// Insert new book returning primary keys.
err := db.Insert(&book)
// INSERT INTO "books" (title, text) VALUES ('my title', 'my text') RETURNING "id"

// Insert new book returning all columns.
err := db.Model(&book).Returning("*").Insert()
// INSERT INTO "books" (title, text) VALUES ('my title', 'my text') RETURNING *

// Select existing book by name or create new book.
err := db.Model(&book).
    Where("title = ?title").
    OnConflict("DO NOTHING"). // optional
    SelectOrInsert()
// 1. SELECT * FROM "books" WHERE title = 'my title'
// 2. INSERT INTO "books" (title, text) VALUES ('my title', 'my text') RETURNING "id"
// 3. go to step 1 on error

// Insert new book or update existing one.
_, err := db.Model(&book).
    OnConflict("(id) DO UPDATE").
    Set("title = ?title").
    Insert()
// INSERT INTO "books" ("id", "title") VALUES (100, 'my title')
// ON CONFLICT (id) DO UPDATE SET title = 'title version #1'
Update
// Update all columns except primary keys.
err := db.Update(&book)
// UPDATE "books" SET title = 'my title', text = 'my text' WHERE id = 1

// Update only column "title".
res, err := db.Model(&book).Set("title = ?title").Where("id = ?id").Update()
// UPDATE "books" SET title = 'my title' WHERE id = 1

// Update only column "title".
res, err := db.Model(&book).Column("title").Update()
// UPDATE "books" SET title = 'my title' WHERE id = 1

// Upper column "title" and scan it.
var title string
res, err := db.Model(&book).
    Set("title = upper(title)").
    Where("id = ?", 1).
    Returning("title").
    Update(&title)
// UPDATE "books" SET title = upper(title) WHERE id = 1 RETURNING title
Delete
// Delete book by primary key.
err := db.Delete(&book)
// DELETE FROM "books" WHERE id = 1

// Delete book by title.
res, err := db.Model(&book).Where("title = ?title").Delete()
// DELETE FROM "books" WHERE title = 'my title'
Has one

Following examples selects users joining their profiles:

type Profile struct {
    Id   int
    Lang string
}

// User has one profile.
type User struct {
    Id        int
    Name      string
    ProfileId int
    Profile   *Profile
}

db := connect()
defer db.Close()

qs := []string{
    "CREATE TEMP TABLE users (id int, name text, profile_id int)",
    "CREATE TEMP TABLE profiles (id int, lang text)",
    "INSERT INTO users VALUES (1, 'user 1', 1), (2, 'user 2', 2)",
    "INSERT INTO profiles VALUES (1, 'en'), (2, 'ru')",
}
for _, q := range qs {
    _, err := db.Exec(q)
    if err != nil {
        panic(err)
    }
}

// Select users joining their profiles with following query:
//
// SELECT
//   "user".*,
//   "profile"."id" AS "profile__id",
//   "profile"."lang" AS "profile__lang"
// FROM "users" AS "user"
// LEFT JOIN "profiles" AS "profile" ON "profile"."id" = "user"."profile_id"

var users []User
err := db.Model(&users).
    Column("user.*", "Profile").
    Select()
if err != nil {
    panic(err)
}

fmt.Println(len(users), "results")
fmt.Println(users[0].Id, users[0].Name, users[0].Profile)
fmt.Println(users[1].Id, users[1].Name, users[1].Profile)
// Output: 2 results
// 1 user 1 &{1 en}
// 2 user 2 &{2 ru}
Belongs to

Following examples selects users joining their profiles:

// Profile belongs to User.
type Profile struct {
    Id     int
    Lang   string
    UserId int
}

type User struct {
    Id      int
    Name    string
    Profile *Profile
}

db := connect()
defer db.Close()

qs := []string{
    "CREATE TEMP TABLE users (id int, name text)",
    "CREATE TEMP TABLE profiles (id int, lang text, user_id int)",
    "INSERT INTO users VALUES (1, 'user 1'), (2, 'user 2')",
    "INSERT INTO profiles VALUES (1, 'en', 1), (2, 'ru', 2)",
}
for _, q := range qs {
    _, err := db.Exec(q)
    if err != nil {
        panic(err)
    }
}

// Select users joining their profiles with following query:
//
// SELECT
//   "user".*,
//   "profile"."id" AS "profile__id",
//   "profile"."lang" AS "profile__lang",
//   "profile"."user_id" AS "profile__user_id"
// FROM "users" AS "user"
// LEFT JOIN "profiles" AS "profile" ON "profile"."user_id" = "user"."id"

var users []User
err := db.Model(&users).
    Column("user.*", "Profile").
    Select()
if err != nil {
    panic(err)
}

fmt.Println(len(users), "results")
fmt.Println(users[0].Id, users[0].Name, users[0].Profile)
fmt.Println(users[1].Id, users[1].Name, users[1].Profile)
// Output: 2 results
// 1 user 1 &{1 en 1}
// 2 user 2 &{2 ru 2}
Has many

Following example selects first user and all his active profiles:

type Profile struct {
    Id     int
    Lang   string
    Active bool
    UserId int
}

// User has many profiles.
type User struct {
    Id       int
    Name     string
    Profiles []*Profile
}

db := connect()
defer db.Close()

qs := []string{
    "CREATE TEMP TABLE users (id int, name text)",
    "CREATE TEMP TABLE profiles (id int, lang text, active bool, user_id int)",
    "INSERT INTO users VALUES (1, 'user 1')",
    "INSERT INTO profiles VALUES (1, 'en', TRUE, 1), (2, 'ru', TRUE, 1), (3, 'md', FALSE, 1)",
}
for _, q := range qs {
    _, err := db.Exec(q)
    if err != nil {
        panic(err)
    }
}

// Select user and all his active profiles using following queries:
//
// SELECT "user".* FROM "users" AS "user" ORDER BY "user"."id" LIMIT 1
//
// SELECT "profile".* FROM "profiles" AS "profile"
// WHERE (active IS TRUE) AND (("profile"."user_id") IN ((1)))

var user User
err := db.Model(&user).
    Column("user.*", "Profiles").
    Relation("Profiles", func(q *orm.Query) *orm.Query {
        return q.Where("active IS TRUE")
    }).
    First()
if err != nil {
    panic(err)
}
fmt.Println(user.Id, user.Name, user.Profiles[0], user.Profiles[1])
// Output: 1 user 1 &{1 en true 1} &{2 ru true 1}
Has many to many

Following example selects one item and all subitems using itermediary item_to_items table.


type Item struct {
    Id    int
    Items []Item `pg:",many2many:item_to_items,joinFK:Sub"`
}

err := db.Model(&item).Column("item.*", "Items").First()
// SELECT "item".* FROM "items" AS "item" ORDER BY "item"."id" LIMIT 1
//
// SELECT * FROM "items" AS "item"
// JOIN "item_to_items" ON ("item_to_items"."item_id") IN ((1))
// WHERE ("item"."id" = "item_to_items"."sub_id")

Howto

Please go through examples to get the idea how to use this package.

FAQ

Why go-pg

  • No rows.Close to manually manage connections.

  • go-pg automatically maps rows on Go structs and slice.

  • go-pg is 2x-10x faster than GORM on querying 100 rows from table.

    BenchmarkQueryRowsGopgOptimized-4          	   10000	    122138 ns/op	   83472 B/op	     625 allocs/op
BenchmarkQueryRowsGopgReflect-4            	   10000	    137208 ns/op	   87488 B/op	     736 allocs/op
BenchmarkQueryRowsGopgORM-4                	   10000	    142029 ns/op	   87920 B/op	     741 allocs/op
BenchmarkQueryRowsStdlibPq-4               	   10000	    162664 ns/op	  161631 B/op	    1324 allocs/op
BenchmarkQueryRowsGORM-4                   	    2000	    569147 ns/op	  415272 B/op	    6966 allocs/op

  • go-pg generates much more effecient queries for joins.

    Has one relation
    BenchmarkModelHasOneGopg-4                 	    5000	    273181 ns/op	   62692 B/op	    1080 allocs/op
BenchmarkModelHasOneGORM-4                 	     500	   3320562 ns/op	 1528489 B/op	   71630 allocs/op

    go-pg:

    db.Model(&books).Column("book.*", "Author").Limit(100).Select()

    SELECT "book".*, "author"."id" AS "author__id", "author"."name" AS "author__name"
FROM "books" AS "book"
LEFT JOIN "authors" AS "author" ON "author"."id" = "book"."author_id"
LIMIT 100

    GORM:

    db.Preload("Author").Limit(100).Find(&books).Error

    SELECT  * FROM "books"   LIMIT 100
SELECT  * FROM "authors"  WHERE ("id" IN ('1','2'...'100'))
    Has many relation
    BenchmarkModelHasManyGopg-4                	     500	   2825899 ns/op	  311556 B/op	    5501 allocs/op
BenchmarkModelHasManyGORM-4                	     200	   7538012 ns/op	 3333023 B/op	   71756 allocs/op

    go-pg:

    db.Model(&books).Column("book.*", "Translations").Limit(100).Select()

    SELECT "book".* FROM "books" AS "book" LIMIT 100
SELECT "translation".* FROM "translations" AS "translation"
WHERE ("translation"."book_id") IN ((100), (101), ... (199));

    GORM:

    db.Preload("Translations").Limit(100).Find(&books).Error

    SELECT * FROM "books" LIMIT 100;
SELECT * FROM "translations"
WHERE ("book_id" IN (1, 2, ..., 100));
SELECT * FROM "authors" WHERE ("book_id" IN (1, 2, ..., 100));
    Many to many relation
    BenchmarkModelHasMany2ManyGopg-4           	     500	   3184262 ns/op	  397883 B/op	    7523 allocs/op
BenchmarkModelHasMany2ManyGORM-4           	     200	   8233222 ns/op	 3686341 B/op	   77236 allocs/op

    go-pg:

    db.Model(&books).Column("book.*", "Genres").Limit(100).Select()

    SELECT "book"."id" FROM "books" AS "book" LIMIT 100;
SELECT * FROM "genres" AS "genre"
JOIN "book_genres" AS "book_genre" ON ("book_genre"."book_id") IN ((1), (2), ..., (100))
WHERE "genre"."id" = "book_genre"."genre_id";

    GORM:

    db.Preload("Genres").Limit(100).Find(&books).Error

    SELECT * FROM "books" LIMIT 100;
SELECT * FROM "genres"
INNER JOIN "book_genres" ON "book_genres"."genre_id" = "genres"."id"
WHERE ("book_genres"."book_id" IN ((1), (2), ..., (100)));
How can I view queries this library generates?

You can setup query logger like this:

pg.SetQueryLogger(log.New(os.Stdout, "", log.LstdFlags))

Or you can configure PostgreSQL to log every query by adding following lines to your postgresql.conf (usually /etc/postgresql/9.5/main/postgresql.conf):

log_statement = 'all'
log_min_duration_statement = 0

Then just tail the log file:

tail -f /var/log/postgresql/postgresql-9.5-main.log

Documentation

Overview

Package gopkg.in/pg.v5 implements a PostgreSQL client.

Example (Placeholders)

go-pg recognizes placeholders (`?`) in queries and replaces them with parameters when queries are executed. Parameters are escaped before replacing according to PostgreSQL rules. Specifically:

  • all parameters are properly quoted against SQL injections;
  • null byte is removed;
  • JSON/JSONB gets `\u0000` escaped as `\\u0000`.
package main

import (
	"fmt"

	"gopkg.in/pg.v5"
)

type Params struct {
	X int
	Y int
}

func (p *Params) Sum() int {
	return p.X + p.Y
}

// go-pg recognizes placeholders (`?`) in queries and replaces them
// with parameters when queries are executed. Parameters are escaped
// before replacing according to PostgreSQL rules. Specifically:
//   - all parameters are properly quoted against SQL injections;
//   - null byte is removed;
//   - JSON/JSONB gets `\u0000` escaped as `\\u0000`.
func main() {
	var num int

	// Simple params.
	_, err := db.Query(pg.Scan(&num), "SELECT ?", 42)
	if err != nil {
		panic(err)
	}
	fmt.Println("simple:", num)

	// Indexed params.
	_, err = db.Query(pg.Scan(&num), "SELECT ?0 + ?0", 1)
	if err != nil {
		panic(err)
	}
	fmt.Println("indexed:", num)

	// Named params.
	params := &Params{
		X: 1,
		Y: 1,
	}
	_, err = db.Query(pg.Scan(&num), "SELECT ?x + ?y + ?Sum", params)
	if err != nil {
		panic(err)
	}
	fmt.Println("named:", num)

	// Global params.
	_, err = db.WithParam("z", 1).Query(pg.Scan(&num), "SELECT ?x + ?y + ?z", params)
	if err != nil {
		panic(err)
	}
	fmt.Println("global:", num)

}

Output:

simple: 42
indexed: 2
named: 4
global: 3

Index

Examples

Constants

This section is empty.

Variables

View Source 
var (
	ErrNoRows    = internal.ErrNoRows
	ErrMultiRows = internal.ErrMultiRows
)
View Source 
var Discard orm.Discard

Discard is used with Query and QueryOne to discard rows.

Functions

func Array 

func Array(v interface{}) *types.Array

Array accepts a slice and returns a wrapper for working with PostgreSQL array data type.

For struct fields you can use array tag: 

Emails  []string `pg:",array"`
Example 
src := []string{"one@example.com", "two@example.com"}
var dst []string
_, err := db.QueryOne(pg.Scan(pg.Array(&dst)), `SELECT ?`, pg.Array(src))
if err != nil {
	panic(err)
}
fmt.Println(dst)

Output:

[one@example.com two@example.com]

func F 

func F(field string) types.ValueAppender

F quotes a SQL identifier such as a table or column name replacing any placeholders found in the field.

Example 
db := modelDB()

var book Book
err := db.Model(&book).Where("? = 1", pg.F("id")).Select()
if err != nil {
	panic(err)
}
fmt.Println(book)

Output:

Book<Id=1 Title="book 1">

func Hstore 

func Hstore(v interface{}) *types.Hstore

Hstore accepts a map and returns a wrapper for working with hstore data type. Supported map types are:

  • map[string]string

For struct fields you can use hstore tag: 

Attrs map[string]string `pg:",hstore"`
Example 
src := map[string]string{"hello": "world"}
var dst map[string]string
_, err := db.QueryOne(pg.Scan(pg.Hstore(&dst)), `SELECT ?`, pg.Hstore(src))
if err != nil {
	panic(err)
}
fmt.Println(dst)

Output:

map[hello:world]

func In 

func In(slice interface{}) types.ValueAppender

In accepts a slice and returns a wrapper that can be used with PostgreSQL IN operator: 

Where("id IN (?)", pg.In([]int{1, 2, 3}))

func Model 

func Model(model ...interface{}) *orm.Query

Model returns new query for the optional model.

func Q 

func Q(query string, params ...interface{}) orm.FormatAppender

Q replaces any placeholders found in the query.

Example 
db := modelDB()

cond := fmt.Sprintf("id = %d", 1)

var book Book
err := db.Model(&book).Where("?", pg.Q(cond)).Select()
if err != nil {
	panic(err)
}
fmt.Println(book)

Output:

Book<Id=1 Title="book 1">

func Scan 

func Scan(values ...interface{}) orm.ColumnScanner

Scan returns ColumnScanner that copies the columns in the row into the values.

Example 
var s1, s2 string
_, err := db.QueryOne(pg.Scan(&s1, &s2), `SELECT ?, ?`, "foo", "bar")
fmt.Println(s1, s2, err)

Output:

foo bar <nil>

func SetLogger 

func SetLogger(logger *log.Logger)

func SetQueryLogger 

func SetQueryLogger(logger *log.Logger)

SetQueryLogger sets a logger that will be used to log generated queries.

Types

type DB 

type DB struct {
	// contains filtered or unexported fields
}

DB is a database handle representing a pool of zero or more underlying connections. It's safe for concurrent use by multiple goroutines.

func Connect 

func Connect(opt *Options) *DB

Connect connects to a database using provided options.

The returned DB is safe for concurrent use by multiple goroutines and maintains its own connection pool.

Example 
db := pg.Connect(&pg.Options{
	User: "postgres",
})
err := db.Close()
fmt.Println(err)

Output:

<nil>

func (*DB) Begin 

func (db *DB) Begin() (*Tx, error)

Begin starts a transaction. Most callers should use RunInTransaction instead.

Example 
db := txExample()

tx, err := db.Begin()
if err != nil {
	panic(err)
}

var counter int
_, err = tx.QueryOne(pg.Scan(&counter), `SELECT counter FROM tx_test`)
if err != nil {
	tx.Rollback()
	panic(err)
}

counter++

_, err = tx.Exec(`UPDATE tx_test SET counter = ?`, counter)
if err != nil {
	tx.Rollback()
	panic(err)
}

err = tx.Commit()
if err != nil {
	panic(err)
}

fmt.Println(counter)

Output:

1

func (*DB) Close 

func (db *DB) Close() error

Close closes the database client, releasing any open resources.

It is rare to Close a DB, as the DB handle is meant to be long-lived and shared between many goroutines.

func (*DB) CopyFrom 

func (db *DB) CopyFrom(reader io.Reader, query interface{}, params ...interface{}) (*types.Result, error)

CopyFrom copies data from reader to a table.

Example 
_, err := db.Exec(`CREATE TEMP TABLE words(word text, len int)`)
if err != nil {
	panic(err)
}

r := strings.NewReader("hello,5\nfoo,3\n")
_, err = db.CopyFrom(r, `COPY words FROM STDIN WITH CSV`)
if err != nil {
	panic(err)
}

var buf bytes.Buffer
_, err = db.CopyTo(&buf, `COPY words TO STDOUT WITH CSV`)
if err != nil {
	panic(err)
}
fmt.Println(buf.String())

Output:

hello,5
foo,3

func (*DB) CopyTo 

func (db *DB) CopyTo(writer io.Writer, query interface{}, params ...interface{}) (*types.Result, error)

CopyTo copies data from a table to writer.

func (*DB) CreateTable 

func (db *DB) CreateTable(model interface{}, opt *orm.CreateTableOptions) error

CreateTable creates table for the model. It recognizes following field tags:

  • notnull - sets NOT NULL constraint.
  • unique - sets UNIQUE constraint.
Example 
type Model struct {
	Id   int
	Name string
}

err := db.CreateTable(&Model{}, &orm.CreateTableOptions{
	Temp: true, // create temp table
})
if err != nil {
	panic(err)
}

var info []struct {
	ColumnName string
	DataType   string
}
_, err = db.Query(&info, `
		SELECT column_name, data_type
		FROM information_schema.columns
		WHERE table_name = 'models'
	`)
if err != nil {
	panic(err)
}
fmt.Println(info)

Output:

[{id bigint} {name text}]

func (*DB) Delete 

func (db *DB) Delete(model interface{}) error

Delete deletes the model by primary key.

Example 
db := modelDB()

book := Book{
	Title:    "title 1",
	AuthorID: 1,
}
err := db.Insert(&book)
if err != nil {
	panic(err)
}

err = db.Delete(&book)
if err != nil {
	panic(err)
}

err = db.Select(&book)
fmt.Println(err)

Output:

pg: no rows in result set
Example (MultipleRows) 
db := modelDB()

ids := pg.In([]int{1, 2, 3})
res, err := db.Model(&Book{}).Where("id IN (?)", ids).Delete()
if err != nil {
	panic(err)
}
fmt.Println("deleted", res.RowsAffected())

count, err := db.Model(&Book{}).Count()
if err != nil {
	panic(err)
}
fmt.Println("left", count)

Output:

deleted 3
left 0

func (*DB) Exec 

func (db *DB) Exec(query interface{}, params ...interface{}) (res *types.Result, err error)

Exec executes a query ignoring returned rows. The params are for any placeholders in the query.

Example 
res, err := db.Exec(`CREATE TEMP TABLE test()`)
fmt.Println(res.RowsAffected(), err)

Output:

-1 <nil>

func (*DB) ExecOne 

func (db *DB) ExecOne(query interface{}, params ...interface{}) (*types.Result, error)

ExecOne acts like Exec, but query must affect only one row. It returns ErrNoRows error when query returns zero rows or ErrMultiRows when query returns multiple rows.

func (*DB) FormatQuery 

func (db *DB) FormatQuery(dst []byte, query string, params ...interface{}) []byte

func (*DB) Insert 

func (db *DB) Insert(model ...interface{}) error

Insert inserts the model updating primary keys if they are empty.

Example 
db := modelDB()

book := Book{
	Title:    "new book",
	AuthorID: 1,
}

err := db.Insert(&book)
if err != nil {
	panic(err)
}
fmt.Println(book)

Output:

Book<Id=4 Title="new book">
Example (BulkInsert) 
db := modelDB()

book1 := Book{
	Title: "new book 1",
}
book2 := Book{
	Title: "new book 2",
}
err := db.Insert(&book1, &book2)
if err != nil {
	panic(err)
}
fmt.Println(book1, book2)

Output:

Book<Id=4 Title="new book 1"> Book<Id=5 Title="new book 2">
Example (BulkInsert2) 
db := modelDB()

books := []Book{{
	Title: "new book 1",
}, {
	Title: "new book 2",
}}
err := db.Insert(&books)
if err != nil {
	panic(err)
}
fmt.Println(books)

Output:

[Book<Id=4 Title="new book 1"> Book<Id=5 Title="new book 2">]
Example (OnConflictDoNothing) 
db := modelDB()

book := Book{
	Id:    100,
	Title: "book 100",
}

for i := 0; i < 2; i++ {
	res, err := db.Model(&book).OnConflict("DO NOTHING").Insert()
	if err != nil {
		panic(err)
	}
	if res.RowsAffected() > 0 {
		fmt.Println("created")
	} else {
		fmt.Println("did nothing")
	}
}

err := db.Delete(&book)
if err != nil {
	panic(err)
}

Output:

created
did nothing
Example (OnConflictDoUpdate) 
db := modelDB()

var book *Book
for i := 0; i < 2; i++ {
	book = &Book{
		Id:    100,
		Title: fmt.Sprintf("title version #%d", i),
	}
	_, err := db.Model(book).
		OnConflict("(id) DO UPDATE").
		Set("title = ?title").
		Insert()
	if err != nil {
		panic(err)
	}

	err = db.Select(book)
	if err != nil {
		panic(err)
	}
	fmt.Println(book)
}

err := db.Delete(book)
if err != nil {
	panic(err)
}

Output:

Book<Id=100 Title="title version #0">
Book<Id=100 Title="title version #1">
Example (SelectOrInsert) 
db := modelDB()

author := Author{
	Name: "R. Scott Bakker",
}
created, err := db.Model(&author).
	Column("id").
	Where("name = ?name").
	OnConflict("DO NOTHING"). // OnConflict is optional
	Returning("id").
	SelectOrInsert()
if err != nil {
	panic(err)
}
fmt.Println(created, author)

Output:

true Author<ID=2 Name="R. Scott Bakker">

func (*DB) Listen 

func (db *DB) Listen(channels ...string) *Listener

Listen listens for notifications sent with NOTIFY command.

func (*DB) Model 

func (db *DB) Model(model ...interface{}) *orm.Query

Model returns new query for the model.

Example 
package main

import (
	"fmt"

	"gopkg.in/pg.v5"
)

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 createSchema(db *pg.DB) error {
	queries := []string{
		`CREATE TEMP TABLE users (id serial, name text, emails jsonb)`,
		`CREATE TEMP TABLE stories (id serial, title text, author_id bigint)`,
	}
	for _, q := range queries {
		_, err := db.Exec(q)
		if err != nil {
			return err
		}
	}
	return nil
}

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

	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.
	var story Story
	err = db.Model(&story).
		Column("story.*", "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]>>
Example (ApplyFunc) 
db := modelDB()

var authorId int
var editorId int

filter := func(q *orm.Query) (*orm.Query, error) {
	if authorId != 0 {
		q = q.Where("author_id = ?", authorId)
	}
	if editorId != 0 {
		q = q.Where("editor_id = ?", editorId)
	}
	return q, nil
}

var books []Book
authorId = 1
err := db.Model(&books).
	Apply(filter).
	Select()
if err != nil {
	panic(err)
}
fmt.Println(books)

Output:

[Book<Id=1 Title="book 1"> Book<Id=2 Title="book 2">]
Example (BelongsTo) 
// Profile belongs to User.
type Profile struct {
	Id     int
	Lang   string
	UserId int
}

type User struct {
	Id      int
	Name    string
	Profile *Profile
}

db := connect()
defer db.Close()

qs := []string{
	"CREATE TEMP TABLE users (id int, name text)",
	"CREATE TEMP TABLE profiles (id int, lang text, user_id int)",
	"INSERT INTO users VALUES (1, 'user 1'), (2, 'user 2')",
	"INSERT INTO profiles VALUES (1, 'en', 1), (2, 'ru', 2)",
}
for _, q := range qs {
	_, err := db.Exec(q)
	if err != nil {
		panic(err)
	}
}

// Select users joining their profiles with following query:
//
// SELECT
//   "user".*,
//   "profile"."id" AS "profile__id",
//   "profile"."lang" AS "profile__lang"
// FROM "users" AS "user"
// LEFT JOIN "profiles" AS "profile" ON "profile"."id" = "user"."profile_id"

var users []User
err := db.Model(&users).
	Column("user.*", "Profile").
	Select()
if err != nil {
	panic(err)
}

fmt.Println(len(users), "results")
fmt.Println(users[0].Id, users[0].Name, users[0].Profile)
fmt.Println(users[1].Id, users[1].Name, users[1].Profile)

Output:

2 results
1 user 1 &{1 en 1}
2 user 2 &{2 ru 2}
Example (Count) 
db := modelDB()

count, err := db.Model(&Book{}).Count()
if err != nil {
	panic(err)
}

fmt.Println(count)

Output:

3
Example (CountEstimate) 
db := modelDB()

count, err := db.Model(&Book{}).CountEstimate(0)
if err != nil {
	panic(err)
}

fmt.Println(count)

Output:

3
Example (HasMany) 
type Profile struct {
	Id     int
	Lang   string
	Active bool
	UserId int
}

// User has many profiles.
type User struct {
	Id       int
	Name     string
	Profiles []*Profile
}

db := connect()
defer db.Close()

qs := []string{
	"CREATE TEMP TABLE users (id int, name text)",
	"CREATE TEMP TABLE profiles (id int, lang text, active bool, user_id int)",
	"INSERT INTO users VALUES (1, 'user 1')",
	"INSERT INTO profiles VALUES (1, 'en', TRUE, 1), (2, 'ru', TRUE, 1), (3, 'md', FALSE, 1)",
}
for _, q := range qs {
	_, err := db.Exec(q)
	if err != nil {
		panic(err)
	}
}

// Select user and all his active profiles with following queries:
//
// SELECT "user".* FROM "users" AS "user" ORDER BY "user"."id" LIMIT 1
//
// SELECT "profile".* FROM "profiles" AS "profile"
// WHERE (active IS TRUE) AND (("profile"."user_id") IN ((1)))

var user User
err := db.Model(&user).
	Column("user.*", "Profiles").
	Relation("Profiles", func(q *orm.Query) (*orm.Query, error) {
		return q.Where("active IS TRUE"), nil
	}).
	First()
if err != nil {
	panic(err)
}
fmt.Println(user.Id, user.Name, user.Profiles[0], user.Profiles[1])

Output:

1 user 1 &{1 en true 1} &{2 ru true 1}
Example (HasManySelf) 
type Item struct {
	Id       int
	Items    []Item `pg:",fk:Parent"`
	ParentId int
}

db := connect()
defer db.Close()

qs := []string{
	"CREATE TEMP TABLE items (id int, parent_id int)",
	"INSERT INTO items VALUES (1, NULL), (2, 1), (3, 1)",
}
for _, q := range qs {
	_, err := db.Exec(q)
	if err != nil {
		panic(err)
	}
}

// Select item and all subitems with following queries:
//
// SELECT "item".* FROM "items" AS "item" ORDER BY "item"."id" LIMIT 1
//
// SELECT "item".* FROM "items" AS "item" WHERE (("item"."parent_id") IN ((1)))

var item Item
err := db.Model(&item).Column("item.*", "Items").First()
if err != nil {
	panic(err)
}
fmt.Println("Item", item.Id)
fmt.Println("Subitems", item.Items[0].Id, item.Items[1].Id)

Output:

Item 1
Subitems 2 3
Example (HasOne) 
type Profile struct {
	Id   int
	Lang string
}

// User has one profile.
type User struct {
	Id        int
	Name      string
	ProfileId int
	Profile   *Profile
}

db := connect()
defer db.Close()

qs := []string{
	"CREATE TEMP TABLE users (id int, name text, profile_id int)",
	"CREATE TEMP TABLE profiles (id int, lang text)",
	"INSERT INTO users VALUES (1, 'user 1', 1), (2, 'user 2', 2)",
	"INSERT INTO profiles VALUES (1, 'en'), (2, 'ru')",
}
for _, q := range qs {
	_, err := db.Exec(q)
	if err != nil {
		panic(err)
	}
}

// Select users joining their profiles with following query:
//
// SELECT
//   "user".*,
//   "profile"."id" AS "profile__id",
//   "profile"."lang" AS "profile__lang",
//   "profile"."user_id" AS "profile__user_id"
// FROM "users" AS "user"
// LEFT JOIN "profiles" AS "profile" ON "profile"."user_id" = "user"."id"

var users []User
err := db.Model(&users).
	Column("user.*", "Profile").
	Select()
if err != nil {
	panic(err)
}

fmt.Println(len(users), "results")
fmt.Println(users[0].Id, users[0].Name, users[0].Profile)
fmt.Println(users[1].Id, users[1].Name, users[1].Profile)

Output:

2 results
1 user 1 &{1 en}
2 user 2 &{2 ru}
Example (HstoreStructTag) 
type Item struct {
	Id    int64
	Attrs map[string]string `pg:",hstore"` // marshalled as PostgreSQL hstore
}

_, err := db.Exec(`CREATE TEMP TABLE items (id serial, attrs hstore)`)
if err != nil {
	panic(err)
}
defer db.Exec("DROP TABLE items")

item1 := Item{
	Id:    1,
	Attrs: map[string]string{"hello": "world"},
}
if err := db.Insert(&item1); err != nil {
	panic(err)
}

var item Item
err = db.Model(&item).Where("id = ?", 1).Select()
if err != nil {
	panic(err)
}
fmt.Println(item)

Output:

{1 map[hello:world]}
Example (ManyToMany) 
type Item struct {
	Id    int
	Items []Item `pg:",many2many:item_to_items,joinFK:Sub"`
}

db := connect()
defer db.Close()

qs := []string{
	"CREATE TEMP TABLE items (id int)",
	"CREATE TEMP TABLE item_to_items (item_id int, sub_id int)",
	"INSERT INTO items VALUES (1), (2), (3)",
	"INSERT INTO item_to_items VALUES (1, 2), (1, 3)",
}
for _, q := range qs {
	_, err := db.Exec(q)
	if err != nil {
		panic(err)
	}
}

// Select item and all subitems with following queries:
//
// SELECT "item".* FROM "items" AS "item" ORDER BY "item"."id" LIMIT 1
//
// SELECT * FROM "items" AS "item"
// JOIN "item_to_items" ON ("item_to_items"."item_id") IN ((1))
// WHERE ("item"."id" = "item_to_items"."sub_id")

var item Item
err := db.Model(&item).Column("item.*", "Items").First()
if err != nil {
	panic(err)
}
fmt.Println("Item", item.Id)
fmt.Println("Subitems", item.Items[0].Id, item.Items[1].Id)

Output:

Item 1
Subitems 2 3
Example (NullEmptyValue) 
type Example struct {
	Hello string
}

var str sql.NullString
_, err := db.QueryOne(pg.Scan(&str), "SELECT ?hello", &Example{Hello: ""})
if err != nil {
	panic(err)
}
fmt.Println(str.Valid)

Output:

false
Example (PostgresArrayStructTag) 
type Item struct {
	Id      int64
	Emails  []string `pg:",array"` // marshalled as PostgreSQL array
	Numbers [][]int  `pg:",array"` // marshalled as PostgreSQL array
}

_, err := db.Exec(`CREATE TEMP TABLE items (id serial, emails text[], numbers int[][])`)
if err != nil {
	panic(err)
}
defer db.Exec("DROP TABLE items")

item1 := Item{
	Id:      1,
	Emails:  []string{"one@example.com", "two@example.com"},
	Numbers: [][]int{{1, 2}, {3, 4}},
}
if err := db.Insert(&item1); err != nil {
	panic(err)
}

var item Item
err = db.Model(&item).Where("id = ?", 1).Select()
if err != nil {
	panic(err)
}
fmt.Println(item)

Output:

{1 [one@example.com two@example.com] [[1 2] [3 4]]}
Example (SelectAndCount) 
db := modelDB()

var books []Book
count, err := db.Model(&books).OrderExpr("id ASC").Limit(2).SelectAndCount()
if err != nil {
	panic(err)
}

fmt.Println(count)
fmt.Println(books)

Output:

3
[Book<Id=1 Title="book 1"> Book<Id=2 Title="book 2">]

func (*DB) Options 

func (db *DB) Options() *Options

Options returns read-only Options that were used to connect to the DB.

func (*DB) Prepare 

func (db *DB) Prepare(q string) (*Stmt, error)

Prepare creates a prepared statement for later queries or executions. Multiple queries or executions may be run concurrently from the returned statement.

Example 
stmt, err := db.Prepare(`SELECT $1::text, $2::text`)
if err != nil {
	panic(err)
}

var s1, s2 string
_, err = stmt.QueryOne(pg.Scan(&s1, &s2), "foo", "bar")
if err != nil {
	panic(err)
}
fmt.Println(s1, s2)

Output:

foo bar

func (*DB) Query 

func (db *DB) Query(model, query interface{}, params ...interface{}) (res *types.Result, err error)

Query executes a query that returns rows, typically a SELECT. The params are for any placeholders in the query.

Example 
package main

import (
	"fmt"

	"gopkg.in/pg.v5"
)

func CreateUser(db *pg.DB, user *User) error {
	_, err := db.QueryOne(user, `
		INSERT INTO users (name, emails) VALUES (?name, ?emails)
		RETURNING id
	`, user)
	return err
}

func GetUser(db *pg.DB, id int64) (*User, error) {
	var user User
	_, err := db.QueryOne(&user, `SELECT * FROM users WHERE id = ?`, id)
	return &user, err
}

func GetUsers(db *pg.DB) ([]User, error) {
	var users []User
	_, err := db.Query(&users, `SELECT * FROM users`)
	return users, err
}

func GetUsersByIds(db *pg.DB, ids []int64) ([]User, error) {
	var users []User
	_, err := db.Query(&users, `SELECT * FROM users WHERE id IN (?)`, pg.In(ids))
	return users, err
}

func CreateStory(db *pg.DB, story *Story) error {
	_, err := db.QueryOne(story, `
		INSERT INTO stories (title, author_id) VALUES (?title, ?author_id)
		RETURNING id
	`, story)
	return err
}

// GetStory returns story with associated author.
func GetStory(db *pg.DB, id int64) (*Story, error) {
	var story Story
	_, err := db.QueryOne(&story, `
		SELECT s.*,
			u.id AS author__id, u.name AS author__name, u.emails AS author__emails
		FROM stories AS s, users AS u
		WHERE s.id = ? AND u.id = s.author_id
	`, id)
	return &story, err
}

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

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

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

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

	story1 := &Story{
		Title:    "Cool story",
		AuthorId: user1.Id,
	}
	err = CreateStory(db, story1)

	user, err := GetUser(db, user1.Id)
	if err != nil {
		panic(err)
	}

	users, err := GetUsers(db)
	if err != nil {
		panic(err)
	}

	story, err := GetStory(db, story1.Id)
	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 (*DB) QueryOne 

func (db *DB) QueryOne(model, query interface{}, params ...interface{}) (*types.Result, error)

QueryOne acts like Query, but query must return only one row. It returns ErrNoRows error when query returns zero rows or ErrMultiRows when query returns multiple rows.

Example 
var user struct {
	Name string
}

res, err := db.QueryOne(&user, `
        WITH users (name) AS (VALUES (?))
        SELECT * FROM users
    `, "admin")
if err != nil {
	panic(err)
}
fmt.Println(res.RowsAffected())
fmt.Println(user)

Output:

1
{admin}
Example (Returning_id) 
_, err := db.Exec(`CREATE TEMP TABLE users(id serial, name varchar(500))`)
if err != nil {
	panic(err)
}

var user struct {
	Id   int32
	Name string
}
user.Name = "admin"

_, err = db.QueryOne(&user, `
        INSERT INTO users (name) VALUES (?name) RETURNING id
    `, &user)
if err != nil {
	panic(err)
}
fmt.Println(user)

Output:

{1 admin}

func (*DB) RunInTransaction 

func (db *DB) RunInTransaction(fn func(*Tx) error) error

RunInTransaction runs a function in a transaction. If function returns an error transaction is rollbacked, otherwise transaction is committed.

Example 
db := txExample()

var counter int
// Transaction is automatically rollbacked on error.
err := db.RunInTransaction(func(tx *pg.Tx) error {
	_, err := tx.QueryOne(pg.Scan(&counter), `SELECT counter FROM tx_test`)
	if err != nil {
		return err
	}

	counter++

	_, err = tx.Exec(`UPDATE tx_test SET counter = ?`, counter)
	return err
})
if err != nil {
	panic(err)
}

fmt.Println(counter)

Output:

1

func (*DB) Select 

func (db *DB) Select(model interface{}) error

Select selects the model by primary key.

Example 
db := modelDB()

book := Book{
	Id: 1,
}
err := db.Select(&book)
if err != nil {
	panic(err)
}
fmt.Println(book)

Output:

Book<Id=1 Title="book 1">
Example (AllColumns) 
db := modelDB()

var book Book
err := db.Model(&book).Column("book.*").First()
if err != nil {
	panic(err)
}
fmt.Println(book, book.AuthorID)

Output:

Book<Id=1 Title="book 1"> 1
Example (FirstRow) 
db := modelDB()

var firstBook Book
err := db.Model(&firstBook).First()
if err != nil {
	panic(err)
}
fmt.Println(firstBook)

Output:

Book<Id=1 Title="book 1">
Example (GroupBy) 
db := modelDB()

var res []struct {
	AuthorId  int
	BookCount int
}

err := db.Model(&Book{}).
	Column("author_id").
	ColumnExpr("count(*) AS book_count").
	Group("author_id").
	OrderExpr("book_count DESC").
	Select(&res)
if err != nil {
	panic(err)
}
fmt.Println("len", len(res))
fmt.Printf("author %d has %d books\n", res[0].AuthorId, res[0].BookCount)
fmt.Printf("author %d has %d books\n", res[1].AuthorId, res[1].BookCount)

Output:

len 2
author 1 has 2 books
author 11 has 1 books
Example (LastRow) 
db := modelDB()

var lastBook Book
err := db.Model(&lastBook).Last()
if err != nil {
	panic(err)
}
fmt.Println(lastBook)

Output:

Book<Id=3 Title="book 3">
Example (SomeColumns) 
db := modelDB()

var book Book
err := db.Model(&book).
	Column("book.id", "book.title").
	OrderExpr("book.id ASC").
	Limit(1).
	Select()
if err != nil {
	panic(err)
}

fmt.Println(book)

Output:

Book<Id=1 Title="book 1">
Example (SomeColumnsIntoVars) 
db := modelDB()

var id int
var title string
err := db.Model(&Book{}).
	Column("book.id", "book.title").
	OrderExpr("book.id ASC").
	Limit(1).
	Select(&id, &title)
if err != nil {
	panic(err)
}

fmt.Println(id, title)

Output:

1 book 1
Example (SqlExpression) 
db := modelDB()

var ids []int
err := db.Model(&Book{}).
	ColumnExpr("array_agg(book.id)").
	Select(pg.Array(&ids))
if err != nil {
	panic(err)
}
fmt.Println(ids)

Output:

[1 2 3]
Example (With) 
authorBooks := db.Model(&Book{}).Where("author_id = ?", 1)

var books []Book
err := db.Model().
	With("author_books", authorBooks).
	Table("author_books").
	Select(&books)
if err != nil {
	panic(err)
}
fmt.Println(books)

Output:

[Book<Id=1 Title="book 1"> Book<Id=2 Title="book 2">]
Example (WrapWith) 
var books []Book
err := db.Model(&books).
	Where("author_id = ?", 1).
	WrapWith("author_books").
	Table("author_books").
	Select(&books)
if err != nil {
	panic(err)
}
fmt.Println(books)

Output:

[Book<Id=1 Title="book 1"> Book<Id=2 Title="book 2">]

func (*DB) String 

func (db *DB) String() string

func (*DB) Update 

func (db *DB) Update(model interface{}) error

Update updates the model by primary key.

Example 
db := modelDB()

err := db.Update(&Book{
	Id:    1,
	Title: "updated book 1",
})
if err != nil {
	panic(err)
}

var book Book
err = db.Model(&book).Where("id = ?", 1).Select()
if err != nil {
	panic(err)
}

fmt.Println(book)

Output:

Book<Id=1 Title="updated book 1">
Example (SetValues) 
db := modelDB()

var book Book
_, err := db.Model(&book).
	Set("title = concat(?, title, ?)", "prefix ", " suffix").
	Where("id = ?", 1).
	Returning("*").
	Update()
if err != nil {
	panic(err)
}

fmt.Println(book)

Output:

Book<Id=1 Title="prefix book 1 suffix">
Example (SomeColumns) 
db := modelDB()

book := Book{
	Id:       1,
	Title:    "updated book 1",
	AuthorID: 2, // this column will not be updated
}
_, err := db.Model(&book).Column("title").Returning("*").Update()
if err != nil {
	panic(err)
}

fmt.Println(book, book.AuthorID)

Output:

Book<Id=1 Title="updated book 1"> 1
Example (SomeColumns2) 
db := modelDB()

book := Book{
	Id:       1,
	Title:    "updated book 1",
	AuthorID: 2, // this column will not be updated
}
_, err := db.Model(&book).Set("title = ?title").Returning("*").Update()
if err != nil {
	panic(err)
}

fmt.Println(book, book.AuthorID)

Output:

Book<Id=1 Title="updated book 1"> 1

func (*DB) WithParam 

func (db *DB) WithParam(param string, value interface{}) *DB

WithParam returns a DB that replaces the param with the value in queries.

func (*DB) WithTimeout 

func (db *DB) WithTimeout(d time.Duration) *DB

WithTimeout returns a DB that uses d as the read/write timeout.

Example 
var count int
// Use bigger timeout since this query is known to be slow.
_, err := db.WithTimeout(time.Minute).QueryOne(pg.Scan(&count), `
		SELECT count(*) FROM big_table
	`)
if err != nil {
	panic(err)
}

Output:

type Error 

type Error interface {
	Field(byte) string
	IntegrityViolation() bool
}

type IntSet 

type IntSet map[int64]struct{}

func (IntSet) AddModel 

func (IntSet) AddModel(_ orm.ColumnScanner) error

func (IntSet) AfterDelete 

func (IntSet) AfterDelete(_ orm.DB) error

func (IntSet) AfterInsert 

func (IntSet) AfterInsert(_ orm.DB) error

func (IntSet) AfterQuery 

func (IntSet) AfterQuery(_ orm.DB) error

func (IntSet) AfterSelect 

func (IntSet) AfterSelect(_ orm.DB) error

func (IntSet) AfterUpdate 

func (IntSet) AfterUpdate(_ orm.DB) error

func (IntSet) BeforeDelete 

func (IntSet) BeforeDelete(_ orm.DB) error

func (IntSet) BeforeInsert 

func (IntSet) BeforeInsert(_ orm.DB) error

func (IntSet) BeforeUpdate 

func (IntSet) BeforeUpdate(_ orm.DB) error

func (*IntSet) NewModel 

func (set *IntSet) NewModel() orm.ColumnScanner

func (*IntSet) Reset 

func (set *IntSet) Reset() error

func (*IntSet) ScanColumn 

func (setptr *IntSet) ScanColumn(colIdx int, colName string, b []byte) error

type Ints 

type Ints []int64
Example 
var nums pg.Ints
_, err := db.Query(&nums, `SELECT generate_series(0, 10)`)
fmt.Println(nums, err)

Output:

[0 1 2 3 4 5 6 7 8 9 10] <nil>

func (Ints) AddModel 

func (Ints) AddModel(_ orm.ColumnScanner) error

func (Ints) AfterDelete 

func (Ints) AfterDelete(_ orm.DB) error

func (Ints) AfterInsert 

func (Ints) AfterInsert(_ orm.DB) error

func (Ints) AfterQuery 

func (Ints) AfterQuery(_ orm.DB) error

func (Ints) AfterSelect 

func (Ints) AfterSelect(_ orm.DB) error

func (Ints) AfterUpdate 

func (Ints) AfterUpdate(_ orm.DB) error

func (Ints) AppendValue 

func (ints Ints) AppendValue(dst []byte, quote int) ([]byte, error)

func (Ints) BeforeDelete 

func (Ints) BeforeDelete(_ orm.DB) error

func (Ints) BeforeInsert 

func (Ints) BeforeInsert(_ orm.DB) error

func (Ints) BeforeUpdate 

func (Ints) BeforeUpdate(_ orm.DB) error

func (*Ints) NewModel 

func (ints *Ints) NewModel() orm.ColumnScanner

func (*Ints) Reset 

func (ints *Ints) Reset() error

func (*Ints) ScanColumn 

func (ints *Ints) ScanColumn(colIdx int, colName string, b []byte) error

type Listener 

type Listener struct {
	// contains filtered or unexported fields
}

Listener listens for notifications sent with NOTIFY command. It's NOT safe for concurrent use by multiple goroutines except the Channel API.

Example 
ln := db.Listen("mychan")
defer ln.Close()

ch := ln.Channel()

go func() {
	_, err := db.Exec("NOTIFY mychan, ?", "hello world")
	if err != nil {
		panic(err)
	}
}()

notif := <-ch
fmt.Println(notif)

Output:

&{mychan hello world}

func (*Listener) Channel 

func (ln *Listener) Channel() <-chan *Notification

Channel returns a channel for concurrently receiving notifications. The channel is closed with Listener.

func (*Listener) Close 

func (ln *Listener) Close() error

Close closes the listener, releasing any open resources.

func (*Listener) Listen 

func (ln *Listener) Listen(channels ...string) error

Listen starts listening for notifications on channels.

func (*Listener) Receive 

func (ln *Listener) Receive() (channel string, payload string, err error)

Receive indefinitely waits for a notification.

func (*Listener) ReceiveTimeout 

func (ln *Listener) ReceiveTimeout(timeout time.Duration) (channel, payload string, err error)

ReceiveTimeout waits for a notification until timeout is reached.

type Notification 

type Notification struct {
	Channel string
	Payload string
}

A notification received with LISTEN command.

type NullTime 

type NullTime struct {
	time.Time
}

NullTime is a time.Time wrapper that marshals zero time as JSON null and PostgreSQL NULL.

func (NullTime) AppendValue 

func (tm NullTime) AppendValue(b []byte, quote int) ([]byte, error)

func (NullTime) MarshalJSON 

func (tm NullTime) MarshalJSON() ([]byte, error)

func (*NullTime) Scan 

func (tm *NullTime) Scan(b interface{}) error

func (*NullTime) UnmarshalJSON 

func (tm *NullTime) UnmarshalJSON(b []byte) error

type Options 

type Options struct {
	// Network type, either tcp or unix.
	// Default is tcp.
	Network string
	// TCP host:port or Unix socket depending on Network.
	Addr string

	// Dialer creates new network connection and has priority over
	// Network and Addr options.
	Dialer func(network, addr string) (net.Conn, error)

	User     string
	Password string
	Database string

	// TLS config for secure connections.
	TLSConfig *tls.Config

	// Maximum number of retries before giving up.
	// Default is to not retry failed queries.
	MaxRetries int
	// Whether to retry queries cancelled because of statement_timeout.
	RetryStatementTimeout bool

	// Dial timeout for establishing new connections.
	// Default is 5 seconds.
	DialTimeout time.Duration
	// Timeout for socket reads. If reached, commands will fail
	// with a timeout instead of blocking.
	ReadTimeout time.Duration
	// Timeout for socket writes. If reached, commands will fail
	// with a timeout instead of blocking.
	WriteTimeout time.Duration

	// Maximum number of socket connections.
	// Default is 20 connections.
	PoolSize int
	// Amount of time client waits for free connection if all
	// connections are busy before returning an error.
	// Default is 5 seconds.
	PoolTimeout time.Duration
	// Amount of time after which client closes idle connections.
	// Default is to not close idle connections.
	IdleTimeout time.Duration
	// Frequency of idle checks.
	// Default is 1 minute.
	IdleCheckFrequency time.Duration

	// When true Tx does not issue BEGIN, COMMIT, or ROLLBACK.
	// Also underlying database connection is immediately returned to the pool.
	// This is primarily useful for running your database tests in one big
	// transaction, because PostgreSQL does not support nested transactions.
	DisableTransaction bool
}

Database connection options.

type Stmt 

type Stmt struct {
	// contains filtered or unexported fields
}

Stmt is a prepared statement. Stmt is safe for concurrent use by multiple goroutines.

func (*Stmt) Close 

func (stmt *Stmt) Close() error

Close closes the statement.

func (*Stmt) Exec 

func (stmt *Stmt) Exec(params ...interface{}) (res *types.Result, err error)

Exec executes a prepared statement with the given parameters.

func (*Stmt) ExecOne 

func (stmt *Stmt) ExecOne(params ...interface{}) (*types.Result, error)

ExecOne acts like Exec, but query must affect only one row. It returns ErrNoRows error when query returns zero rows or ErrMultiRows when query returns multiple rows.

func (*Stmt) Query 

func (stmt *Stmt) Query(model interface{}, params ...interface{}) (res *types.Result, err error)

Query executes a prepared query statement with the given parameters.

func (*Stmt) QueryOne 

func (stmt *Stmt) QueryOne(model interface{}, params ...interface{}) (*types.Result, error)

QueryOne acts like Query, but query must return only one row. It returns ErrNoRows error when query returns zero rows or ErrMultiRows when query returns multiple rows.

type Strings 

type Strings []string
Example 
var strs pg.Strings
_, err := db.Query(&strs, `
		WITH users AS (VALUES ('foo'), ('bar')) SELECT * FROM users
	`)
fmt.Println(strs, err)

Output:

[foo bar] <nil>

func (Strings) AddModel 

func (Strings) AddModel(_ orm.ColumnScanner) error

func (Strings) AfterDelete 

func (Strings) AfterDelete(_ orm.DB) error

func (Strings) AfterInsert 

func (Strings) AfterInsert(_ orm.DB) error

func (Strings) AfterQuery 

func (Strings) AfterQuery(_ orm.DB) error

func (Strings) AfterSelect 

func (Strings) AfterSelect(_ orm.DB) error

func (Strings) AfterUpdate 

func (Strings) AfterUpdate(_ orm.DB) error

func (Strings) AppendValue 

func (strings Strings) AppendValue(dst []byte, quote int) ([]byte, error)

func (Strings) BeforeDelete 

func (Strings) BeforeDelete(_ orm.DB) error

func (Strings) BeforeInsert 

func (Strings) BeforeInsert(_ orm.DB) error

func (Strings) BeforeUpdate 

func (Strings) BeforeUpdate(_ orm.DB) error

func (*Strings) NewModel 

func (strings *Strings) NewModel() orm.ColumnScanner

func (*Strings) Reset 

func (strings *Strings) Reset() error

func (*Strings) ScanColumn 

func (strings *Strings) ScanColumn(colIdx int, _ string, b []byte) error

type Tx 

type Tx struct {
	// contains filtered or unexported fields
}

Tx is an in-progress database transaction.

A transaction must end with a call to Commit or Rollback.

After a call to Commit or Rollback, all operations on the transaction fail with ErrTxDone.

The statements prepared for a transaction by calling the transaction's Prepare or Stmt methods are closed by the call to Commit or Rollback.

func (*Tx) Begin 

func (tx *Tx) Begin() (*Tx, error)

Begin returns the transaction.

func (*Tx) Commit 

func (tx *Tx) Commit() error

Commit commits the transaction.

func (*Tx) CopyFrom 

func (tx *Tx) CopyFrom(r io.Reader, query string, params ...interface{}) (*types.Result, error)

CopyFrom copies data from reader to a table.

func (*Tx) CreateTable 

func (tx *Tx) CreateTable(model interface{}, opt *orm.CreateTableOptions) error

CreateTable creates table for the model. It recognizes following field tags:

  • notnull - sets NOT NULL constraint.
  • unique - sets UNIQUE constraint.

func (*Tx) Delete 

func (tx *Tx) Delete(model interface{}) error

Delete deletes the model by primary key.

func (*Tx) Exec 

func (tx *Tx) Exec(query interface{}, params ...interface{}) (*types.Result, error)

Exec executes a query with the given parameters in a transaction.

func (*Tx) ExecOne 

func (tx *Tx) ExecOne(query interface{}, params ...interface{}) (*types.Result, error)

ExecOne acts like Exec, but query must affect only one row. It returns ErrNoRows error when query returns zero rows or ErrMultiRows when query returns multiple rows.

func (*Tx) FormatQuery 

func (tx *Tx) FormatQuery(dst []byte, query string, params ...interface{}) []byte

func (*Tx) Insert 

func (tx *Tx) Insert(model ...interface{}) error

Insert inserts the model updating primary keys if they are empty.

func (*Tx) Model 

func (tx *Tx) Model(model ...interface{}) *orm.Query

Model returns new query for the model.

func (*Tx) Prepare 

func (tx *Tx) Prepare(q string) (*Stmt, error)

Prepare creates a prepared statement for use within a transaction.

The returned statement operates within the transaction and can no longer be used once the transaction has been committed or rolled back.

To use an existing prepared statement on this transaction, see Tx.Stmt.

func (*Tx) Query 

func (tx *Tx) Query(model interface{}, query interface{}, params ...interface{}) (*types.Result, error)

Query executes a query with the given parameters in a transaction.

func (*Tx) QueryOne 

func (tx *Tx) QueryOne(model interface{}, query interface{}, params ...interface{}) (*types.Result, error)

QueryOne acts like Query, but query must return only one row. It returns ErrNoRows error when query returns zero rows or ErrMultiRows when query returns multiple rows.

func (*Tx) Rollback 

func (tx *Tx) Rollback() error

Rollback aborts the transaction.

func (*Tx) RunInTransaction 

func (tx *Tx) RunInTransaction(fn func(*Tx) error) error

RunInTransaction runs a function in the transaction. If function returns an error transaction is rollbacked, otherwise transaction is committed.

func (*Tx) Select 

func (tx *Tx) Select(model interface{}) error

Select selects the model by primary key.

func (*Tx) Stmt 

func (tx *Tx) Stmt(stmt *Stmt) *Stmt

Stmt returns a transaction-specific prepared statement from an existing statement.

func (*Tx) Update 

func (tx *Tx) Update(model interface{}) error

Update updates the model by primary key.

Source Files

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Path Synopsis
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