This tutorial shows you how build a simple CRUD Go application with CockroachDB and the Go pgx driver.
Step 1. Start CockroachDB
Create a free cluster
- If you haven't already, sign up for a CockroachDB Cloud account.
- Log in to your CockroachDB Cloud account.
- On the Clusters page, click Create Cluster.
- On the Create your cluster page, select Serverless.
Click Create cluster.
Your cluster will be created in a few seconds and the Create SQL user dialog will display.
Create a SQL user
The Create SQL user dialog allows you to create a new SQL user and password.
- Enter a username in the SQL user field or use the one provided by default.
- Click Generate & save password.
- Copy the generated password and save it in a secure location.
Click Next.
Currently, all new users are created with full privileges. For more information and to change the default settings, see [Manage SQL users on a cluster.
Get the connection string
The Connect to cluster dialog shows information about how to connect to your cluster.
- Select General connection string from the Select option dropdown.
Open the General connection string section, then copy the connection string provided and save it in a secure location.
The sample application used in this tutorial uses system CA certificates for server certificate verification, so you can skip the Download CA Cert instructions.
Note:The connection string is pre-populated with your username, password, cluster name, and other details. Your password, in particular, will be provided only once. Save it in a secure place (Cockroach Labs recommends a password manager) to connect to your cluster in the future. If you forget your password, you can reset it by going to the SQL Users page for the cluster, found at
https://cockroachlabs.cloud/cluster/<CLUSTER ID>/users
.
- If you haven't already, download the CockroachDB binary.
Run the
cockroach start-single-node
command:$ cockroach start-single-node --advertise-addr 'localhost' --insecure
This starts an insecure, single-node cluster.
Take note of the following connection information in the SQL shell welcome text:
CockroachDB node starting at 2021-08-30 17:25:30.06524 +0000 UTC (took 4.3s) build: CCL v21.1.6 @ 2021/07/20 15:33:43 (go1.15.11) webui: http://localhost:8080 sql: postgresql://root@localhost:26257?sslmode=disable
You'll use the
sql
connection string to connect to the cluster later in this tutorial.
The --insecure
flag used in this tutorial is intended for non-production testing only. To run CockroachDB in production, use a secure cluster instead.
Step 2. Get the code
Clone the code's GitHub repo:
$ git clone https://github.com/cockroachlabs/example-app-go-pgx/
The project has the following directory structure:
├── README.md
├── dbinit.sql
└── main.go
The dbinit.sql
file initializes the database schema that the application uses:
CREATE TABLE accounts (
id UUID PRIMARY KEY,
balance INT8
);
The main.go
file contains the code for INSERT
, SELECT
, UPDATE
, and DELETE
SQL operations. The file also executes the main
method of the program.
package main
import (
"context"
"log"
"os"
crdbpgx "github.com/cockroachdb/cockroach-go/v2/crdb/crdbpgxv5"
"github.com/google/uuid"
"github.com/jackc/pgx/v5"
)
func main() {
// Read in connection string
config, err := pgx.ParseConfig(os.Getenv("DATABASE_URL"))
if err != nil {
log.Fatalf("error parsing connection configuration: %v", err)
}
config.RuntimeParams["application_name"] = "$ docs_simplecrud_gopgx"
conn, err := pgx.ConnectConfig(context.Background(), config)
if err != nil {
log.Fatalf("error connecting to database: %v", err)
}
defer conn.Close(context.Background())
// Set up table
err = crdbpgx.ExecuteTx(context.Background(), conn, pgx.TxOptions{}, func(tx pgx.Tx) error {
return initTable(context.Background(), tx)
})
if err != nil {
log.Fatalf("error initializing table: %v", err)
}
// Insert initial rows
var accounts [4]uuid.UUID
for i := 0; i < len(accounts); i++ {
accounts[i] = uuid.New()
}
err = crdbpgx.ExecuteTx(context.Background(), conn, pgx.TxOptions{}, func(tx pgx.Tx) error {
return insertRows(context.Background(), tx, accounts)
})
if err != nil {
log.Fatalf("error insertin rows: %v", err)
}
log.Println("New rows created.")
// Print out the balances
log.Println("Initial balances:")
printBalances(conn)
// Run a transfer
err = crdbpgx.ExecuteTx(context.Background(), conn, pgx.TxOptions{}, func(tx pgx.Tx) error {
return transferFunds(context.Background(), tx, accounts[2], accounts[1], 100)
})
if err != nil {
log.Fatalf("error transferring funds: %v", err)
}
log.Println("Transfer successful.")
// Print out the balances
log.Println("Balances after transfer:")
printBalances(conn)
// Delete rows
err = crdbpgx.ExecuteTx(context.Background(), conn, pgx.TxOptions{}, func(tx pgx.Tx) error {
return deleteRows(context.Background(), tx, accounts[0], accounts[1])
})
if err != nil {
log.Fatalf("error deleting rows: %v", err)
}
log.Println("Rows deleted.")
// Print out the balances
log.Println("Balances after deletion:")
printBalances(conn)
}
func initTable(ctx context.Context, tx pgx.Tx) error {
// Dropping existing table if it exists
log.Println("Drop existing accounts table if necessary.")
if _, err := tx.Exec(ctx, "DROP TABLE IF EXISTS accounts"); err != nil {
return err
}
// Create the accounts table
log.Println("Creating accounts table.")
if _, err := tx.Exec(ctx,
"CREATE TABLE accounts (id UUID PRIMARY KEY DEFAULT gen_random_uuid(), balance INT8)"); err != nil {
return err
}
return nil
}
func insertRows(ctx context.Context, tx pgx.Tx, accts [4]uuid.UUID) error {
// Insert four rows into the "accounts" table.
log.Println("Creating new rows...")
if _, err := tx.Exec(ctx,
"INSERT INTO accounts (id, balance) VALUES ($1, $2), ($3, $4), ($5, $6), ($7, $8)", accts[0], 250, accts[1], 100, accts[2], 500, accts[3], 300); err != nil {
return err
}
return nil
}
func printBalances(conn *pgx.Conn) error {
rows, err := conn.Query(context.Background(), "SELECT id, balance FROM accounts")
if err != nil {
log.Fatal(err)
}
defer rows.Close()
for rows.Next() {
var id uuid.UUID
var balance int
if err := rows.Scan(&id, &balance); err != nil {
log.Fatal(err)
}
log.Printf("%s: %d\n", id, balance)
}
return nil
}
func transferFunds(ctx context.Context, tx pgx.Tx, from uuid.UUID, to uuid.UUID, amount int) error {
// Read the balance.
var fromBalance int
if err := tx.QueryRow(ctx,
"SELECT balance FROM accounts WHERE id = $1", from).Scan(&fromBalance); err != nil {
return err
}
if fromBalance < amount {
log.Println("insufficient funds")
}
// Perform the transfer.
log.Printf("Transferring funds from account with ID %s to account with ID %s...", from, to)
if _, err := tx.Exec(ctx,
"UPDATE accounts SET balance = balance - $1 WHERE id = $2", amount, from); err != nil {
return err
}
if _, err := tx.Exec(ctx,
"UPDATE accounts SET balance = balance + $1 WHERE id = $2", amount, to); err != nil {
return err
}
return nil
}
func deleteRows(ctx context.Context, tx pgx.Tx, one uuid.UUID, two uuid.UUID) error {
// Delete two rows into the "accounts" table.
log.Printf("Deleting rows with IDs %s and %s...", one, two)
if _, err := tx.Exec(ctx,
"DELETE FROM accounts WHERE id IN ($1, $2)", one, two); err != nil {
return err
}
return nil
}
CockroachDB may require the client to retry a transaction in the case of read/write contention. The CockroachDB Go client includes a generic retry function (ExecuteTx()
) that runs inside a transaction and retries it as needed. The code sample shows how you can use this function to wrap SQL statements.
Step 3. Initialize the database
Navigate to the
example-app-go-pgx
directory:$ cd example-app-go-pgx
Set the
DATABASE_URL
environment variable to the connection string for your cluster:export DATABASE_URL="postgresql://root@localhost:26257?sslmode=disable"
export DATABASE_URL="{connection-string}"
Where
{connection-string}
is the connection string you obtained from the CockroachDB Cloud Console.To initialize the example database, use the
cockroach sql
command to execute the SQL statements in thedbinit.sql
file:cat dbinit.sql | cockroach sql --url $DATABASE_URL
The SQL statement in the initialization file should execute:
CREATE TABLE Time: 102ms
Step 4. Run the code
Initialize the module:
$ go mod init basic-sample && go mod tidy
Run the code:
$ go run main.go
The output should look similar to the following:
2021/07/20 14:48:02 Creating new rows... 2021/07/20 14:48:02 New rows created. 2021/07/20 14:48:02 Initial balances: 2021/07/20 14:48:02 3a936990-a0c9-45bf-bc24-92e10d91dca9: 300 2021/07/20 14:48:02 8d1849dd-9222-4b12-a4ff-94e583b544a8: 250 2021/07/20 14:48:02 c6ae8917-d24e-4115-b719-f663dbfb9ffb: 500 2021/07/20 14:48:02 d0ce1f5c-e468-4899-8590-2bb6076247f2: 100 2021/07/20 14:48:02 Transferring funds from account with ID c6ae8917-d24e-4115-b719-f663dbfb9ffb to account with ID d0ce1f5c-e468-4899-8590-2bb6076247f2... 2021/07/20 14:48:02 Transfer successful. 2021/07/20 14:48:02 Balances after transfer: 2021/07/20 14:48:02 3a936990-a0c9-45bf-bc24-92e10d91dca9: 300 2021/07/20 14:48:02 8d1849dd-9222-4b12-a4ff-94e583b544a8: 250 2021/07/20 14:48:02 c6ae8917-d24e-4115-b719-f663dbfb9ffb: 400 2021/07/20 14:48:02 d0ce1f5c-e468-4899-8590-2bb6076247f2: 200 2021/07/20 14:48:02 Deleting rows with IDs 8d1849dd-9222-4b12-a4ff-94e583b544a8 and d0ce1f5c-e468-4899-8590-2bb6076247f2... 2021/07/20 14:48:02 Rows deleted. 2021/07/20 14:48:02 Balances after deletion: 2021/07/20 14:48:02 3a936990-a0c9-45bf-bc24-92e10d91dca9: 300 2021/07/20 14:48:02 c6ae8917-d24e-4115-b719-f663dbfb9ffb: 400
As shown in the output, the code does the following:
- Inserts some rows into the
accounts
table. - Reads values from the table.
- Updates values in the table.
- Deletes values from the table.
- Inserts some rows into the
What's next?
Read more about using the Go pgx driver.
You might also be interested in the following pages: