OK

cmd/dbinit/main.go

@@ -0,0 +1,40 @@
+// Command dbinit creates the configured PostgreSQL database when it is absent.
+package main
+
+import (
+	"context"
+	"flag"
+	"fmt"
+	"log"
+	"net/url"
+
+	"github.com/jackc/pgx/v5"
+)
+
+func main() {
+	dsn := flag.String("dsn", "", "PostgreSQL DSN for the target database")
+	flag.Parse()
+	parsed, err := url.Parse(*dsn)
+	if err != nil || parsed.Path == "" {
+		log.Fatal("无效 DSN")
+	}
+	database := parsed.Path[1:]
+	parsed.Path = "/postgres"
+	conn, err := pgx.Connect(context.Background(), parsed.String())
+	if err != nil {
+		log.Fatal(err)
+	}
+	defer conn.Close(context.Background())
+	var exists bool
+	err = conn.QueryRow(context.Background(), "SELECT EXISTS(SELECT 1 FROM pg_database WHERE datname=$1)", database).Scan(&exists)
+	if err != nil {
+		log.Fatal(err)
+	}
+	if !exists {
+		_, err = conn.Exec(context.Background(), "CREATE DATABASE "+pgx.Identifier{database}.Sanitize())
+		if err != nil {
+			log.Fatal(err)
+		}
+	}
+	fmt.Printf("database %s ready\n", database)
+}