fix(postgres): duplicate snapshot name

Fix postgres snapshot name reuse by removing its template flag before
trying to delete it.

Fixes #2822

modules/postgres/postgres.go

@@ -217,6 +217,7 @@ func (c *PostgresContainer) Snapshot(ctx context.Context, opts ...SnapshotOption
 	// execute the commands to create the snapshot, in order
 	if err := c.execCommandsSQL(ctx,
 		// Drop the snapshot database if it already exists
+		fmt.Sprintf(`UPDATE pg_database SET datistemplate = FALSE WHERE datname = '%s'`, snapshotName),
 		fmt.Sprintf(`DROP DATABASE IF EXISTS "%s"`, snapshotName),
 		// Create a copy of the database to another database to use as a template now that it was fully migrated
 		fmt.Sprintf(`CREATE DATABASE "%s" WITH TEMPLATE "%s" OWNER "%s"`, snapshotName, c.dbName, c.user),

modules/postgres/postgres_test.go

@@ -340,6 +340,34 @@ func TestSnapshotWithOverrides(t *testing.T) {
 	})
 }
 
+func TestSnapshotDuplicate(t *testing.T) {
+	ctx := context.Background()
+
+	dbname := "other-db"
+	user := "other-user"
+	password := "other-password"
+
+	ctr, err := postgres.Run(
+		ctx,
+		"docker.io/postgres:16-alpine",
+		postgres.WithDatabase(dbname),
+		postgres.WithUsername(user),
+		postgres.WithPassword(password),
+		postgres.BasicWaitStrategies(),
+	)
+	testcontainers.CleanupContainer(t, ctr)
+	require.NoError(t, err)
+
+	_, _, err = ctr.Exec(ctx, []string{"psql", "-U", user, "-d", dbname, "-c", "CREATE TABLE users (id SERIAL, name TEXT NOT NULL, age INT NOT NULL)"})
+	require.NoError(t, err)
+
+	err = ctr.Snapshot(ctx, postgres.WithSnapshotName("other-snapshot"))
+	require.NoError(t, err)
+
+	err = ctr.Snapshot(ctx, postgres.WithSnapshotName("other-snapshot"))
+	require.NoError(t, err)
+}
+
 func TestSnapshotWithDockerExecFallback(t *testing.T) {
 	ctx := context.Background()