// Benchmarking Append() with transactions.
func BenchmarkAppendTxUpper(b *testing.B) {
	var sess db.Database
	var err error

	if sess, err = db.Open(Adapter, settings); err != nil {
		b.Fatal(err)
	}

	defer sess.Close()

	var tx db.Tx
	if tx, err = sess.Transaction(); err != nil {
		b.Fatal(err)
	}

	var artist db.Collection
	if artist, err = tx.Collection("artist"); err != nil {
		b.Fatal(err)
	}

	if err = artist.Truncate(); err != nil {
		b.Fatal(err)
	}

	item := struct {
		Name string `db:"name"`
	}{"Hayao Miyazaki"}

	b.ResetTimer()
	for i := 0; i < b.N; i++ {
		if _, err = artist.Append(item); err != nil {
			b.Fatal(err)
		}
	}

	if err = tx.Commit(); err != nil {
		b.Fatal(err)
	}
}
// Attempts to test database transactions.
func TestTransactionsAndRollback(t *testing.T) {
	var sess db.Database
	var err error

	type artistType struct {
		ID   int64  `db:"id,omitempty"`
		Name string `db:"name"`
	}

	if sess, err = db.Open(Adapter, settings); err != nil {
		t.Fatal(err)
	}

	defer sess.Close()

	// Simple transaction that should not fail.
	var tx db.Tx
	if tx, err = sess.Transaction(); err != nil {
		t.Fatal(err)
	}

	var artist db.Collection
	if artist, err = tx.Collection("artist"); err != nil {
		t.Fatal(err)
	}

	if err = artist.Truncate(); err != nil {
		t.Fatal(err)
	}

	// Simple transaction
	if _, err = artist.Append(artistType{1, "First"}); err != nil {
		t.Fatal(err)
	}

	if err = tx.Commit(); err != nil {
		t.Fatal(err)
	}

	// Attempt to use the same transaction should fail.
	if _, err = tx.Collection("artist"); err == nil {
		t.Fatalf("Illegal, transaction has already been commited.")
	}

	// Use another transaction.
	if tx, err = sess.Transaction(); err != nil {
		t.Fatal(err)
	}

	if artist, err = tx.Collection("artist"); err != nil {
		t.Fatal(err)
	}

	// Won't fail.
	if _, err = artist.Append(artistType{2, "Second"}); err != nil {
		t.Fatal(err)
	}

	// Won't fail.
	if _, err = artist.Append(artistType{3, "Third"}); err != nil {
		t.Fatal(err)
	}

	// Will fail.
	if _, err = artist.Append(artistType{1, "Duplicated"}); err == nil {
		t.Fatal("Should have failed, as we have already inserted ID 1.")
	}

	if err = tx.Rollback(); err != nil {
		t.Fatal(err)
	}

	if err = tx.Commit(); err == nil {
		t.Fatalf("Should have failed, as we've already rolled back.")
	}

	// Let's verify we still have one element.
	if artist, err = sess.Collection("artist"); err != nil {
		t.Fatal(err)
	}

	var count uint64
	if count, err = artist.Find().Count(); err != nil {
		t.Fatal(err)
	}

	if count != 1 {
		t.Fatalf("Expecting only one element.")
	}

	// Attempt to add some rows.
	if tx, err = sess.Transaction(); err != nil {
		t.Fatal(err)
	}

	if artist, err = tx.Collection("artist"); err != nil {
		t.Fatal(err)
	}

	// Won't fail.
	if _, err = artist.Append(artistType{2, "Second"}); err != nil {
		t.Fatal(err)
	}

	// Won't fail.
	if _, err = artist.Append(artistType{3, "Third"}); err != nil {
		t.Fatal(err)
	}

	// Then rollback for no reason.
	if err = tx.Rollback(); err != nil {
		t.Fatal(err)
	}

	if err = tx.Commit(); err == nil {
		t.Fatalf("Should have failed, as we've already rolled back.")
	}

	// Let's verify we still have one element.
	if artist, err = sess.Collection("artist"); err != nil {
		t.Fatal(err)
	}

	if count, err = artist.Find().Count(); err != nil {
		t.Fatal(err)
	}

	if count != 1 {
		t.Fatalf("Expecting only one element.")
	}

	// Attempt to add some rows.
	if tx, err = sess.Transaction(); err != nil {
		t.Fatal(err)
	}

	if artist, err = tx.Collection("artist"); err != nil {
		t.Fatal(err)
	}

	// Won't fail.
	if _, err = artist.Append(artistType{2, "Second"}); err != nil {
		t.Fatal(err)
	}

	// Won't fail.
	if _, err = artist.Append(artistType{3, "Third"}); err != nil {
		t.Fatal(err)
	}

	if err = tx.Commit(); err != nil {
		t.Fatal(err)
	}

	if err = tx.Rollback(); err == nil {
		t.Fatalf("Should have failed, as we've already commited.")
	}

	// Let's verify we have 3 rows.
	if artist, err = sess.Collection("artist"); err != nil {
		t.Fatal(err)
	}

	if count, err = artist.Find().Count(); err != nil {
		t.Fatal(err)
	}

	if count != 3 {
		t.Fatalf("Expecting 3 elements.")
	}

}