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path: root/src/database/sql/example_test.go
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Diffstat (limited to 'src/database/sql/example_test.go')
-rw-r--r--src/database/sql/example_test.go77
1 files changed, 54 insertions, 23 deletions
diff --git a/src/database/sql/example_test.go b/src/database/sql/example_test.go
index da938b071a..6f9bd91276 100644
--- a/src/database/sql/example_test.go
+++ b/src/database/sql/example_test.go
@@ -13,8 +13,10 @@ import (
"time"
)
-var ctx = context.Background()
-var db *sql.DB
+var (
+ ctx context.Context
+ db *sql.DB
+)
func ExampleDB_QueryContext() {
age := 27
@@ -24,13 +26,25 @@ func ExampleDB_QueryContext() {
}
defer rows.Close()
names := make([]string, 0)
+
for rows.Next() {
var name string
if err := rows.Scan(&name); err != nil {
+ // Check for a scan error.
+ // Query rows will be closed with defer.
log.Fatal(err)
}
names = append(names, name)
}
+ // If the database is being written to ensure to check for Close
+ // errors that may be returned from the driver. The query may
+ // encounter an auto-commit error and be forced to rollback changes.
+ rerr := rows.Close()
+ if rerr != nil {
+ log.Fatal(err)
+ }
+
+ // Rows.Err will report the last error encountered by Rows.Scan.
if err := rows.Err(); err != nil {
log.Fatal(err)
}
@@ -44,11 +58,11 @@ func ExampleDB_QueryRowContext() {
err := db.QueryRowContext(ctx, "SELECT username, created_at FROM users WHERE id=?", id).Scan(&username, &created)
switch {
case err == sql.ErrNoRows:
- log.Printf("No user with id %d", id)
+ log.Printf("no user with id %d\n", id)
case err != nil:
- log.Fatal(err)
+ log.Fatalf("query error: %v\n", err)
default:
- fmt.Printf("Username is %s, account created on %s\n", username, created)
+ log.Printf("username is %q, account created on %s\n", username, created)
}
}
@@ -63,7 +77,7 @@ func ExampleDB_ExecContext() {
log.Fatal(err)
}
if rows != 1 {
- panic(err)
+ log.Fatalf("expected to affect 1 row, affected %d", rows)
}
}
@@ -104,10 +118,10 @@ from
if err := rows.Scan(&id, &name); err != nil {
log.Fatal(err)
}
- fmt.Printf("id %d name is %s\n", id, name)
+ log.Printf("id %d name is %s\n", id, name)
}
if !rows.NextResultSet() {
- log.Fatal("expected more result sets", rows.Err())
+ log.Fatalf("expected more result sets: %v", rows.Err())
}
var roleMap = map[int64]string{
1: "user",
@@ -122,7 +136,7 @@ from
if err := rows.Scan(&id, &role); err != nil {
log.Fatal(err)
}
- fmt.Printf("id %d has role %s\n", id, roleMap[role])
+ log.Printf("id %d has role %s\n", id, roleMap[role])
}
if err := rows.Err(); err != nil {
log.Fatal(err)
@@ -130,11 +144,23 @@ from
}
func ExampleDB_PingContext() {
+ // Ping and PingContext may be used to determine if communication with
+ // the database server is still possible.
+ //
+ // When used in a command line application Ping may be used to establish
+ // that further queries are possible; that the provided DSN is valid.
+ //
+ // When used in long running service Ping may be part of the health
+ // checking system.
+
ctx, cancel := context.WithTimeout(ctx, 1*time.Second)
defer cancel()
+
+ status := "up"
if err := db.PingContext(ctx); err != nil {
- log.Fatal(err)
+ status = "down"
}
+ log.Println(status)
}
func ExampleConn_BeginTx() {
@@ -162,7 +188,7 @@ func ExampleConn_ExecContext() {
}
defer conn.Close() // Return the connection to the pool.
id := 41
- result, err := conn.ExecContext(ctx, `UPDATE balances SET balance = balance + 10 WHERE user_id = ?`, id)
+ result, err := conn.ExecContext(ctx, `UPDATE balances SET balance = balance + 10 WHERE user_id = ?;`, id)
if err != nil {
log.Fatal(err)
}
@@ -171,7 +197,7 @@ func ExampleConn_ExecContext() {
log.Fatal(err)
}
if rows != 1 {
- panic(err)
+ log.Fatalf("expected single row affected, got %d rows affected", rows)
}
}
@@ -184,9 +210,9 @@ func ExampleTx_ExecContext() {
_, execErr := tx.ExecContext(ctx, "UPDATE users SET status = ? WHERE id = ?", "paid", id)
if execErr != nil {
if rollbackErr := tx.Rollback(); rollbackErr != nil {
- log.Printf("Could not roll back: %v\n", rollbackErr)
+ log.Fatalf("update failed: %v, unable to rollback: %v\n", execErr, rollbackErr)
}
- log.Fatal(execErr)
+ log.Fatalf("update failed: %v", execErr)
}
if err := tx.Commit(); err != nil {
log.Fatal(err)
@@ -199,17 +225,17 @@ func ExampleTx_Rollback() {
log.Fatal(err)
}
id := 53
- _, err = tx.ExecContext(ctx, "UPDATE drivers SET status = ? WHERE id = ?", "assigned", id)
+ _, err = tx.ExecContext(ctx, "UPDATE drivers SET status = ? WHERE id = ?;", "assigned", id)
if err != nil {
if rollbackErr := tx.Rollback(); rollbackErr != nil {
- log.Printf("Could not roll back: %v\n", rollbackErr)
+ log.Fatalf("update drivers: unable to rollback: %v", rollbackErr)
}
log.Fatal(err)
}
- _, err = tx.ExecContext(ctx, "UPDATE pickups SET driver_id = $1", id)
+ _, err = tx.ExecContext(ctx, "UPDATE pickups SET driver_id = $1;", id)
if err != nil {
if rollbackErr := tx.Rollback(); rollbackErr != nil {
- log.Printf("Could not roll back: %v\n", rollbackErr)
+ log.Fatalf("update failed: %v, unable to back: %v", err, rollbackErr)
}
log.Fatal(err)
}
@@ -225,17 +251,18 @@ func ExampleStmt() {
log.Fatal(err)
}
defer stmt.Close()
+
// Then reuse it each time you need to issue the query.
id := 43
var username string
err = stmt.QueryRowContext(ctx, id).Scan(&username)
switch {
case err == sql.ErrNoRows:
- log.Printf("No user with that ID.")
+ log.Fatalf("no user with id %d", id)
case err != nil:
log.Fatal(err)
default:
- fmt.Printf("Username is %s\n", username)
+ log.Printf("username is %s\n", username)
}
}
@@ -245,17 +272,19 @@ func ExampleStmt_QueryRowContext() {
if err != nil {
log.Fatal(err)
}
+ defer stmt.Close()
+
// Then reuse it each time you need to issue the query.
id := 43
var username string
err = stmt.QueryRowContext(ctx, id).Scan(&username)
switch {
case err == sql.ErrNoRows:
- log.Printf("No user with that ID.")
+ log.Fatalf("no user with id %d", id)
case err != nil:
log.Fatal(err)
default:
- fmt.Printf("Username is %s\n", username)
+ log.Printf("username is %s\n", username)
}
}
@@ -266,6 +295,7 @@ func ExampleRows() {
log.Fatal(err)
}
defer rows.Close()
+
names := make([]string, 0)
for rows.Next() {
var name string
@@ -274,8 +304,9 @@ func ExampleRows() {
}
names = append(names, name)
}
+ // Check for errors from iterating over rows.
if err := rows.Err(); err != nil {
log.Fatal(err)
}
- fmt.Printf("%s are %d years old", strings.Join(names, ", "), age)
+ log.Printf("%s are %d years old", strings.Join(names, ", "), age)
}
generated by cgit v1.3 (git 2.53.0) at 2026-04-15 20:13:24 +0000