Connecting from Go
Connecting from Go

Connecting from Go

Connecting from Go

Pre-requisites

Before we proceed:

  1. Install the go-tarantool library.

  2. Start Tarantool (locally or in Docker) and make sure that you have created and populated a database as we suggested earlier:

    box.cfg{listen = 3301}
    s = box.schema.space.create('tester')
    s:format({
             {name = 'id', type = 'unsigned'},
             {name = 'band_name', type = 'string'},
             {name = 'year', type = 'unsigned'}
             })
    s:create_index('primary', {
             type = 'hash',
             parts = {'id'}
             })
    s:create_index('secondary', {
             type = 'hash',
             parts = {'band_name'}
             })
    s:insert{1, 'Roxette', 1986}
    s:insert{2, 'Scorpions', 2015}
    s:insert{3, 'Ace of Base', 1993}
    

    Important

    Please do not close the terminal window where Tarantool is running – you’ll need it soon.

  3. In order to connect to Tarantool as an administrator, reset the password for the admin user:

    box.schema.user.passwd('pass')
    

Connecting to Tarantool

To get connected to the Tarantool server, write a simple Go program:

package main

import (
    "fmt"

    "github.com/tarantool/go-tarantool"
)

func main() {
    conn, err := tarantool.Connect("127.0.0.1:3301", tarantool.Opts{})

    if err != nil {
            fmt.Println("Connection refused")
    }

    defer conn.Close()

    // Your logic for interacting with the database
}

You can also specify the user name and password, if needed:

opts := tarantool.Opts{User: "username", Pass: "password"}
conn, err := tarantool.Connect("127.0.0.1:3301", opts)
...

The default user is guest.

Manipulating the data

Inserting data

To insert a tuple into a space, use Insert:

resp, err = conn.Insert("tester", []interface{}{4, "ABBA", 1972})

This inserts the tuple (4, "ABBA", 1972) into a space named tester.

The response code and data are available in the tarantool.Response structure:

code := resp.Code
data := resp.Data

Querying data

To select a tuple from a space, use Select:

resp, err = conn.Select("tester", "primary", 0, 1, tarantool.IterEq, []interface{}{4})

This selects a tuple by the primary key with offset = 0 and limit = 1 from a space named tester (in our example, this is the index named primary, based on the id field of each tuple).

Next, select tuples by a secondary key.

resp, err = conn.Select("tester", "secondary", 0, 1, tarantool.IterEq, []interface{}{"ABBA"})

Finally, select all the tuples in a space:

resp, err = conn.Select("tester", "primary", 0, tarantool.KeyLimit, tarantool.IterAll, []interface{}{})

For more examples, see https://github.com/tarantool/go-tarantool#usage

Updating data

Update a field value using Update:

resp, err = conn.Update("tester", "primary", []interface{}{4}, []interface{}{[]interface{}{"+", 2, 3}})

This increases by 3 the value of field 2 in the tuple with id = 4. If a tuple with this id doesn’t exist, Tarantool will return an error.

Now use Replace to totally replace the tuple that matches the primary key. If a tuple with this primary key doesn’t exist, Tarantool will do nothing.

resp, err = conn.Replace("tester", []interface{}{4, "New band", 2011})

You can also update the data using Upsert that works similarly to Update, but creates a new tuple if the old one was not found.

resp, err = conn.Upsert("tester", []interface{}{4, "Another band", 2000}, []interface{}{[]interface{}{"+", 2, 5}})

This increases by 5 the value of the third field in the tuple with id = 4, – or inserts the tuple (4, "Another band", 2000) if a tuple with this id doesn’t exist.

Deleting data

To delete a tuple, use сonnection.Delete:

resp, err = conn.Delete("tester", "primary", []interface{}{4})

To delete all tuples in a space (or to delete an entire space), use Call. We’ll focus on this function in more detail in the next section.

To delete all tuples in a space, call space:truncate:

resp, err = conn.Call("box.space.tester:truncate", []interface{}{})

To delete an entire space, call space:drop. This requires connecting to Tarantool as the admin user:

resp, err = conn.Call("box.space.tester:drop", []interface{}{})

Executing stored procedures

Switch to the terminal window where Tarantool is running.

Note

If you don’t have a terminal window with remote connection to Tarantool, check out these guides:

Define a simple Lua function:

function sum(a, b)
    return a + b
end

Now we have a Lua function defined in Tarantool. To invoke this function from go, use Call:

resp, err = conn.Call("sum", []interface{}{2, 3})

To send bare Lua code for execution, use Eval:

resp, err = connection.Eval("return 4 + 5", []interface{}{})