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
Organizations without billing information on file can only create one CockroachDB Serverless 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 Select a plan page, select Serverless.
- On the Cloud & Regions page, select a cloud provider (GCP or AWS) in the Cloud provider section.
- In the Regions section, select a region for the cluster. Refer to CockroachDB Cloud Regions for the regions where CockroachDB Serverless clusters can be deployed. To create a multi-region cluster, click Add region and select additional regions. A cluster can have at most six regions.
- Click Next: Capacity.
- On the Capacity page, select Start for free. Click Next: Finalize.
On the Finalize page, click Create cluster.
Your cluster will be created in a few seconds and the Create SQL user dialog will display.
Set up your cluster connection
Navigate to the cluster's Overview page, and select Connect.
Under the Connection String tab, download the cluster certificate.
Take note of the connection string provided. You'll use it to connect to the database later in this tutorial.
- 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
To initialize the example database, use the cockroach sql
command to execute the SQL statements in the dbinit.sql
file:
cat dbinit.sql | cockroach sql --url "<connection-string>"
Where <connection-string>
is the connection string you obtained earlier from the CockroachDB Cloud Console.
cat dbinit.sql | cockroach sql --url "postgresql://root@localhost:26257?sslmode=disable"
postgresql://root@localhost:26257?sslmode=disable
is the sql
connection string you obtained earlier from the cockroach
welcome text.
The SQL statements in the initialization file should execute:
SET
Time: 1ms
SET
Time: 2ms
DROP DATABASE
Time: 1ms
CREATE DATABASE
Time: 2ms
SET
Time: 10ms
CREATE TABLE
Time: 4ms
Step 4. Run the code
Initialize the module:
$ go mod init basic-sample && go mod tidy
Run the code:
$ go run main.go
The program will prompt you for a connection string to the database:
Enter a connection string:
Enter the connection string to your running cluster.
Tip:postgresql://root@localhost:26257?sslmode=disable
should be thesql
connection URL provided in thecockroach
welcome text.Tip:Use the connection string provided in the Connection info window of the CockroachDB Cloud Console.
Note:You need to provide a SQL user password in order to securely connect to a CockroachDB Cloud cluster. The connection string should have a placeholder for the password (
<ENTER-PASSWORD>
).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
To verify that the SQL statements were executed, run the following query from inside the SQL shell:
> USE bank;
> SELECT id, balance FROM accounts;
The output should look similar to the following:
id | balance ---------------------------------------+---------- 3a936990-a0c9-45bf-bc24-92e10d91dca9 | 300 c6ae8917-d24e-4115-b719-f663dbfb9ffb | 400 (2 rows)
What's next?
Read more about using the Go pgx driver.
You might also be interested in the following pages: