pg-dao

Data Access Object for PostgreSQL for Distributed Lab projects.

Usage

package main

import (
	"errors"

	pg "github.com/olegfomenko/pg-dao"
	"gitlab.com/distributed_lab/kit/kv"
)

type Entry struct {
	Id   int64  `db:"id" structs:"-"`
	Name string `db:"name" structs:"name"`
}

func main() {
	// Loading config
	cfg := config.New(kv.MustFromEnv())

	// Creating DAO instance for table "entries"
	dao := pg.NewDAO(cfg.DB(), "entries")

	// Saving record
	// id - saved entry index
	id, err := dao.Create(Entry{
		Name: "First Entry",
	})

	// Cloning DAO for new session
	dao = dao.Clone()

	// Cleaning queries in DAO in current session
	dao = dao.New()

	// Updating entry
	err = dao.UpdateWhereID(id).UpdateColumn("name", "New First Entry").Update()

	// Getting entry by id
	var entry Entry
	// if ok is false - there is no entry with provided id
	ok, err := dao.New().FilterByID(id).Get(&entry)

	// Getting entry by field
	ok, err = dao.New().FilterByColumn("name", "New First Entry").Get(&entry)

	// Deleting entry
	err = dao.New().DeleteWhereID(id).Delete()

	// Creating transaction
	err = dao.Clone().TransactionSerializable(
		func(q pg.DAO) error {
			ok, err := q.FilterByID(id).Get(&entry)
			if err != nil {
				// rollback transaction
				return err
			}

			if !ok {
				// entry does not exist
				return errors.New("not found")
			}

			err = q.New().UpdateWhereID(id).UpdateColumn("name", "Updated First Entry").Update()
			if err != nil {
				// rollback transaction
				return err
			}

			// commit transaction
			return nil
		},
	)
}