Connect an application

The PQ driver is a popular driver for PostgreSQL. Use the driver to connect to YugabyteDB to execute DMLs and DDLs using the standard database/sql package.

CRUD operations

For Go Applications, most drivers provide database connectivity through the standard database/sql API. The following sections break down the example to demonstrate how to perform common tasks required for Go application development using the PQ driver.

To start building your application, make sure you have met the prerequisites.

Step 1: Import the driver package

Import the PQ driver package by adding the following import statement in your Go code.

import (
  _ "github.com/lib/pq"
)

To install the package locally, run the following commands:

Note

Set the environment variable GO111MODULE before installing the lib/pq package if your Go version is 1.11 or higher. 
export GO111MODULE=auto
go get github.com/lib/pq

Step 2: Set up the database connection

Go applications can connect to YugabyteDB using the sql.Open() function. The sql package includes all the functions or structs required for working with YugabyteDB.

Use the sql.Open() function to create a connection object for the YugabyteDB database. This can be used for performing DDLs and DMLs against the database.

The connection details can be specified either as string parameters or via a URL in the following format:

postgresql://username:password@hostname:port/database

Code snippet for connecting to YugabyteDB:

psqlInfo := fmt.Sprintf("host=%s port=%d user=%s password=%s dbname=%s",
                        host, port, user, password, dbname)
// Other connection configs are read from the standard environment variables:
// PGSSLMODE, PGSSLROOTCERT, and so on.
db, err := sql.Open("postgres", psqlInfo)
defer db.Close()
if err != nil {
    log.Fatal(err)
}
Parameter Description Default
user User connecting to the database yugabyte
password User password yugabyte
host Hostname of the YugabyteDB instance localhost
port Listen port for YSQL 5433
dbname Database name yugabyte

Use SSL

For a YugabyteDB Managed cluster, or a YugabyteDB cluster with SSL/TLS enabled, set the SSL-related environment variables as below at the client side. SSL/TLS is enabled by default for client-side authentication. Refer to Configure SSL/TLS for the default and supported modes.

$ export PGSSLMODE=verify-ca
$ export PGSSLROOTCERT=~/root.crt  # Here, the CA certificate file is downloaded as `root.crt` under home directory. Modify your path accordingly.
Environment Variable Description
PGSSLMODE SSL mode used for the connection
PGSSLROOTCERT Path to the root certificate on your computer

Step 3: Write your application

Create a file called QuickStart.go and add the following contents into it:

package main

import (
  "database/sql"
  "fmt"
  "log"

  _ "github.com/lib/pq"
)

const (
  host     = "127.0.0.1"
  port     = 5433
  user     = "yugabyte"
  password = "yugabyte"
  dbname   = "yugabyte"
)

func main() {
    psqlInfo := fmt.Sprintf("host=%s port=%d user=%s password=%s dbname=%s",
                            host, port, user, password, dbname)
    // Other connection configs are read from the standard environment variables:
    // PGSSLMODE, PGSSLROOTCERT, and so on.
    db, err := sql.Open("postgres", psqlInfo)
    if err != nil {
        log.Fatal(err)
    }

    var dropStmt = `DROP TABLE IF EXISTS employee`;
    if _, err := db.Exec(dropStmt); err != nil {
        log.Fatal(err)
    }
    // The `conn.Exec()` function also returns an `error` object which,
    // if not `nil`, needs to be handled in your code.
    var createStmt = `CREATE TABLE employee (id int PRIMARY KEY,
                                             name varchar,
                                             age int,
                                             language varchar)`;
    if _, err := db.Exec(createStmt); err != nil {
        log.Fatal(err)
    }
    fmt.Println("Created table employee")

    // Insert data using the conn.Exec() function.
    var insertStmt string = "INSERT INTO employee(id, name, age, language)" +
        " VALUES (1, 'John', 35, 'Go')";
    if _, err := db.Exec(insertStmt); err != nil {
        log.Fatal(err)
    }
    fmt.Printf("Inserted data: %s\n", insertStmt)

    // Execute the `SELECT` statement using the function `Query()` on `db` instance.
    var name string
    var age int
    var language string
    rows, err := db.Query(`SELECT name, age, language FROM employee WHERE id = 1`)
    if err != nil {
        log.Fatal(err)
    }
    defer rows.Close()
    fmt.Printf("Query for id=1 returned: ");
    // Results are returned as `rows` which can be iterated using `rows.next()` method.
    for rows.Next() {
        // Use `rows.Scan()` for reading the data.
        err := rows.Scan(&name, &age, &language)
        if err != nil {
           log.Fatal(err)
        }
        fmt.Printf("Row[%s, %d, %s]\n", name, age, language)
    }
    err = rows.Err()
    if err != nil {
        log.Fatal(err)
    }

    defer db.Close()
}

The const values are set to the defaults for a local installation of YugabyteDB. If you're using YugabyteDB Managed, replace the values as follows:

  • host - The host address of your cluster. The host address is displayed on the cluster Settings tab.
  • user - Your YugabyteDB database username. In YugabyteDB Managed, the default user is admin.
  • password - Your YugabyteDB database password.
  • dbname - The name of the YugabyteDB database. The default name is yugabyte.
  • port is set to 5433, which is the default port for the YSQL API.

Run the project QuickStartApp.go using the following command:

go run QuickStartApp.go

You should see output similar to the following:

Created table employee
Inserted data: INSERT INTO employee(id, name, age, language) VALUES (1, 'John', 35, 'Go')
Query for id=1 returned: Row[John, 35, Go]

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