Go Relational Persistence

Update 2016-11-13: Future versions

As many of the maintainers have become busy with other projects, progress toward the ever-elusive v2 has slowed to the point that we're only occasionally making progress outside of merging pull requests. In the interest of continuing to release, I'd like to lean toward a more maintainable path forward.

For the moment, I am releasing a v2 tag with the current feature set from master, as some of those features have been actively used and relied on by more than one project. Our next goal is to continue cleaning up the code base with non-breaking changes as much as possible, but if/when a breaking change is needed, we'll just release new versions. This allows us to continue development at whatever pace we're capable of, without delaying the release of features or refusing PRs.

Introduction

I hesitate to call gorp an ORM. Go doesn't really have objects, at least not in the classic Smalltalk/Java sense. There goes the "O". gorp doesn't know anything about the relationships between your structs (at least not yet). So the "R" is questionable too (but I use it in the name because, well, it seemed more clever).

The "M" is alive and well. Given some Go structs and a database, gorp should remove a fair amount of boilerplate busy-work from your code.

I hope that gorp saves you time, minimizes the drudgery of getting data in and out of your database, and helps your code focus on algorithms, not infrastructure.

• Bind struct fields to table columns via API or tag
• Support for embedded structs
• Support for transactions
• Forward engineer db schema from structs (great for unit tests)
• Pre/post insert/update/delete hooks
• Automatically generate insert/update/delete statements for a struct
• Automatic binding of auto increment PKs back to struct after insert
• Delete by primary key(s)
• Select by primary key(s)
• Optional trace sql logging
• Bind arbitrary SQL queries to a struct
• Bind slice to SELECT query results without type assertions
• Use positional or named bind parameters in custom SELECT queries
• Optional optimistic locking using a version column (for update/deletes)

Installation

Use go get or your favorite vendoring tool, using whichever import path you'd like.

Versioning

We use semantic version tags. Feel free to import through gopkg.in (e.g. gopkg.in/gorp.v2) to get the latest tag for a major version, or check out the tag using your favorite vendoring tool.

Development is not very active right now, but we have plans to restructure gorp as we continue to move toward a more extensible system. Whenever a breaking change is needed, the major version will be bumped.

The master branch is where all development is done, and breaking changes may happen from time to time. That said, if you want to live on the bleeding edge and are comfortable updating your code when we make a breaking change, you may use github.com/go-gorp/gorp as your import path.

Check the version tags to see what's available. We'll make a good faith effort to add badges for new versions, but we make no guarantees.

Supported Go versions

This package is guaranteed to be compatible with the latest 2 major versions of Go.

Any earlier versions are only supported on a best effort basis and can be dropped any time. Go has a great compatibility promise. Upgrading your program to a newer version of Go should never really be a problem.

Migration guide

Pre-v2 to v2

Automatic mapping of the version column used in optimistic locking has been removed as it could cause problems if the type was not int. The version column must now explicitly be set with tablemap.SetVersionCol().

Help/Support

Use our gitter channel. We used to use IRC, but with most of us being pulled in many directions, we often need the email notifications from gitter to yell at us to sign in.

Quickstart

package main

import (
    "database/sql"
    "gopkg.in/gorp.v1"
    _ "github.com/mattn/go-sqlite3"
    "log"
    "time"
)

func main() {
    // initialize the DbMap
    dbmap := initDb()
    defer dbmap.Db.Close()

    // delete any existing rows
    err := dbmap.TruncateTables()
    checkErr(err, "TruncateTables failed")

    // create two posts
    p1 := newPost("Go 1.1 released!", "Lorem ipsum lorem ipsum")
    p2 := newPost("Go 1.2 released!", "Lorem ipsum lorem ipsum")

    // insert rows - auto increment PKs will be set properly after the insert
    err = dbmap.Insert(&p1, &p2)
    checkErr(err, "Insert failed")

    // use convenience SelectInt
    count, err := dbmap.SelectInt("select count(*) from posts")
    checkErr(err, "select count(*) failed")
    log.Println("Rows after inserting:", count)

    // update a row
    p2.Title = "Go 1.2 is better than ever"
    count, err = dbmap.Update(&p2)
    checkErr(err, "Update failed")
    log.Println("Rows updated:", count)

    // fetch one row - note use of "post_id" instead of "Id" since column is aliased
    //
    // Postgres users should use $1 instead of ? placeholders
    // See 'Known Issues' below
    //
    err = dbmap.SelectOne(&p2, "select * from posts where post_id=?", p2.Id)
    checkErr(err, "SelectOne failed")
    log.Println("p2 row:", p2)

    // fetch all rows
    var posts []Post
    _, err = dbmap.Select(&posts, "select * from posts order by post_id")
    checkErr(err, "Select failed")
    log.Println("All rows:")
    for x, p := range posts {
        log.Printf("    %d: %v\n", x, p)
    }

    // delete row by PK
    count, err = dbmap.Delete(&p1)
    checkErr(err, "Delete failed")
    log.Println("Rows deleted:", count)

    // delete row manually via Exec
    _, err = dbmap.Exec("delete from posts where post_id=?", p2.Id)
    checkErr(err, "Exec failed")

    // confirm count is zero
    count, err = dbmap.SelectInt("select count(*) from posts")
    checkErr(err, "select count(*) failed")
    log.Println("Row count - should be zero:", count)

    log.Println("Done!")
}

type Post struct {
    // db tag lets you specify the column name if it differs from the struct field
    Id      int64  `db:"post_id"`
    Created int64
    Title   string `db:",size:50"`               // Column size set to 50
    Body    string `db:"article_body,size:1024"` // Set both column name and size
}

func newPost(title, body string) Post {
    return Post{
        Created: time.Now().UnixNano(),
        Title:   title,
        Body:    body,
    }
}

func initDb() *gorp.DbMap {
    // connect to db using standard Go database/sql API
    // use whatever database/sql driver you wish
    db, err := sql.Open("sqlite3", "/tmp/post_db.bin")
    checkErr(err, "sql.Open failed")

    // construct a gorp DbMap
    dbmap := &gorp.DbMap{Db: db, Dialect: gorp.SqliteDialect{}}

    // add a table, setting the table name to 'posts' and
    // specifying that the Id property is an auto incrementing PK
    dbmap.AddTableWithName(Post{}, "posts").SetKeys(true, "Id")

    // create the table. in a production system you'd generally
    // use a migration tool, or create the tables via scripts
    err = dbmap.CreateTablesIfNotExists()
    checkErr(err, "Create tables failed")

    return dbmap
}

func checkErr(err error, msg string) {
    if err != nil {
        log.Fatalln(msg, err)
    }
}

Examples

Mapping structs to tables

First define some types:

type Invoice struct {
    Id       int64
    Created  int64
    Updated  int64
    Memo     string
    PersonId int64
}

type Person struct {
    Id      int64
    Created int64
    Updated int64
    FName   string
    LName   string
}

// Example of using tags to alias fields to column names
// The 'db' value is the column name
//
// A hyphen will cause gorp to skip this field, similar to the
// Go json package.
//
// This is equivalent to using the ColMap methods:
//
//   table := dbmap.AddTableWithName(Product{}, "product")
//   table.ColMap("Id").Rename("product_id")
//   table.ColMap("Price").Rename("unit_price")
//   table.ColMap("IgnoreMe").SetTransient(true)
//
// You can optionally declare the field to be a primary key and/or autoincrement
//
type Product struct {
    Id         int64     `db:"product_id, primarykey, autoincrement"`
    Price      int64     `db:"unit_price"`
    IgnoreMe   string    `db:"-"`
}

Then create a mapper, typically you'd do this one time at app startup:

// connect to db using standard Go database/sql API
// use whatever database/sql driver you wish
db, err := sql.Open("mymysql", "tcp:localhost:3306*mydb/myuser/mypassword")

// construct a gorp DbMap
dbmap := &gorp.DbMap{Db: db, Dialect: gorp.MySQLDialect{"InnoDB", "UTF8"}}

// register the structs you wish to use with gorp
// you can also use the shorter dbmap.AddTable() if you
// don't want to override the table name
//
// SetKeys(true) means we have a auto increment primary key, which
// will get automatically bound to your struct post-insert
//
t1 := dbmap.AddTableWithName(Invoice{}, "invoice_test").SetKeys(true, "Id")
t2 := dbmap.AddTableWithName(Person{}, "person_test").SetKeys(true, "Id")
t3 := dbmap.AddTableWithName(Product{}, "product_test").SetKeys(true, "Id")

Struct Embedding

gorp supports embedding structs. For example:

type Names struct {
    FirstName string
    LastName  string
}

type WithEmbeddedStruct struct {
    Id int64
    Names
}

es := &WithEmbeddedStruct{-1, Names{FirstName: "Alice", LastName: "Smith"}}
err := dbmap.Insert(es)

See the TestWithEmbeddedStruct function in gorp_test.go for a full example.

Create/Drop Tables

Automatically create / drop registered tables. This is useful for unit tests but is entirely optional. You can of course use gorp with tables created manually, or with a separate migration tool (like sql-migrate, goose or migrate).

// create all registered tables
dbmap.CreateTables()

// same as above, but uses "if not exists" clause to skip tables that are
// already defined
dbmap.CreateTablesIfNotExists()

// drop
dbmap.DropTables()

SQL Logging

Optionally you can pass in a logger to trace all SQL statements. I recommend enabling this initially while you're getting the feel for what gorp is doing on your behalf.

Gorp defines a GorpLogger interface that Go's built in log.Logger satisfies. However, you can write your own GorpLogger implementation, or use a package such as glog if you want more control over how statements are logged.

// Will log all SQL statements + args as they are run
// The first arg is a string prefix to prepend to all log messages
dbmap.TraceOn("[gorp]", log.New(os.Stdout, "myapp:", log.Lmicroseconds))

// Turn off tracing
dbmap.TraceOff()

Insert

// Must declare as pointers so optional callback hooks
// can operate on your data, not copies
inv1 := &Invoice{0, 100, 200, "first order", 0}
inv2 := &Invoice{0, 100, 200, "second order", 0}

// Insert your rows
err := dbmap.Insert(inv1, inv2)

// Because we called SetKeys(true) on Invoice, the Id field
// will be populated after the Insert() automatically
fmt.Printf("inv1.Id=%d  inv2.Id=%d\n", inv1.Id, inv2.Id)

Update

Continuing the above example, use the Update method to modify an Invoice:

// count is the # of rows updated, which should be 1 in this example
count, err := dbmap.Update(inv1)

Delete

If you have primary key(s) defined for a struct, you can use the Delete method to remove rows:

count, err := dbmap.Delete(inv1)

Select by Key

Use the Get method to fetch a single row by primary key. It returns nil if no row is found.

// fetch Invoice with Id=99
obj, err := dbmap.Get(Invoice{}, 99)
inv := obj.(*Invoice)

Ad Hoc SQL

SELECT

Select() and SelectOne() provide a simple way to bind arbitrary queries to a slice or a single struct.

// Select a slice - first return value is not needed when a slice pointer is passed to Select()
var posts []Post
_, err := dbmap.Select(&posts, "select * from post order by id")

// You can also use primitive types
var ids []string
_, err := dbmap.Select(&ids, "select id from post")

// Select a single row.
// Returns an error if no row found, or if more than one row is found
var post Post
err := dbmap.SelectOne(&post, "select * from post where id=?", id)

Want to do joins? Just write the SQL and the struct. gorp will bind them:

```go // Define a type for your join // It must contain all the columns in your SELECT statement // // The names here should match the aliased column names you specify // in your SQL - no additional binding work required. simple. // type InvoicePersonView struct { InvoiceId int64 PersonId int64 Memo string FName string }

// Create some rows p1 := &Person{0, 0, 0, "bob", "smith"} err = dbmap.Insert(p1) checkErr(err, "Insert failed")

// notice how we can wire up p1.Id to the invoice easily inv1 := &Invoice{0, 0, 0, "xmas order", p1.Id} err = dbmap.Insert(inv1) checkErr(err, "Insert failed")

// Run your query query := "select i.Id InvoiceId, p.Id PersonId, i.Memo, p.FName " + "from invoice_test i, person_test p " + "where i.PersonId = p.Id"

// pass a slice to Select() var list []InvoicePersonView _, err := dbmap.Select(&list, query)

// this should test true expected := InvoicePersonView{inv1.Id, p1.Id, inv1.Memo, p1.FName} if reflect.DeepEqual(list[0], expected) { fmt.Println("Woot! My join work