Resplit Begin and BeginEx

This is in preparation for a Begin / Tx interface that will similate
nested transactions with savepoints.

In addition, this passes the TxOptions struct by value and thereby
removes an allocation.

batch_test.go

@@ -463,7 +463,7 @@ func TestTxSendBatch(t *testing.T) {
 	);`
 	mustExec(t, conn, sql)
 
-	tx, _ := conn.Begin(context.Background(), nil)
+	tx, _ := conn.Begin(context.Background())
 	batch := &pgx.Batch{}
 	batch.Queue("insert into ledger1(description) values($1) returning id",
 		[]interface{}{"q1"},
@@ -538,7 +538,7 @@ func TestTxSendBatchRollback(t *testing.T) {
 	);`
 	mustExec(t, conn, sql)
 
-	tx, _ := conn.Begin(context.Background(), nil)
+	tx, _ := conn.Begin(context.Background())
 	batch := &pgx.Batch{}
 	batch.Queue("insert into ledger1(description) values($1) returning id",
 		[]interface{}{"q1"},

bench_test.go

@@ -413,7 +413,7 @@ func benchmarkWriteNRowsViaInsert(b *testing.B, n int) {
 	for i := 0; i < b.N; i++ {
 		src := newBenchmarkWriteTableCopyFromSrc(n)
 
-		tx, err := conn.Begin(context.Background(), nil)
+		tx, err := conn.Begin(context.Background())
 		if err != nil {
 			b.Fatal(err)
 		}
@@ -452,7 +452,7 @@ func multiInsert(conn *pgx.Conn, tableName string, columnNames []string, rowSrc
 	}
 	resetQuery()
 
-	tx, err := conn.Begin(context.Background(), nil)
+	tx, err := conn.Begin(context.Background())
 	if err != nil {
 		return 0, err
 	}

large_objects_test.go

@@ -22,7 +22,7 @@ func TestLargeObjects(t *testing.T) {
 		t.Fatal(err)
 	}
 
-	tx, err := conn.Begin(ctx, nil)
+	tx, err := conn.Begin(ctx)
 	if err != nil {
 		t.Fatal(err)
 	}
@@ -135,7 +135,7 @@ func TestLargeObjectsMultipleTransactions(t *testing.T) {
 		t.Fatal(err)
 	}
 
-	tx, err := conn.Begin(ctx, nil)
+	tx, err := conn.Begin(ctx)
 	if err != nil {
 		t.Fatal(err)
 	}
@@ -175,7 +175,7 @@ func TestLargeObjectsMultipleTransactions(t *testing.T) {
 	rows.Close()
 
 	// Start a new transaction
-	tx2, err := conn.Begin(ctx, nil)
+	tx2, err := conn.Begin(ctx)
 	if err != nil {
 		t.Fatal(err)
 	}

pgxpool/conn.go

@@ -66,8 +66,12 @@ func (c *Conn) CopyFrom(ctx context.Context, tableName pgx.Identifier, columnNam
 	return c.Conn().CopyFrom(ctx, tableName, columnNames, rowSrc)
 }
 
-func (c *Conn) Begin(ctx context.Context, txOptions *pgx.TxOptions) (*pgx.Tx, error) {
-	return c.Conn().Begin(ctx, txOptions)
+func (c *Conn) Begin(ctx context.Context) (*pgx.Tx, error) {
+	return c.Conn().Begin(ctx)
+}
+
+func (c *Conn) BeginEx(ctx context.Context, txOptions pgx.TxOptions) (*pgx.Tx, error) {
+	return c.Conn().BeginEx(ctx, txOptions)
 }
 
 func (c *Conn) Conn() *pgx.Conn {

pgxpool/pool.go

@@ -352,13 +352,16 @@ func (p *Pool) SendBatch(ctx context.Context, b *pgx.Batch) pgx.BatchResults {
 	return &poolBatchResults{br: br, c: c}
 }
 
-func (p *Pool) Begin(ctx context.Context, txOptions *pgx.TxOptions) (*Tx, error) {
+func (p *Pool) Begin(ctx context.Context) (*Tx, error) {
+	return p.BeginEx(ctx, pgx.TxOptions{})
+}
+func (p *Pool) BeginEx(ctx context.Context, txOptions pgx.TxOptions) (*Tx, error) {
 	c, err := p.Acquire(ctx)
 	if err != nil {
 		return nil, err
 	}
 
-	t, err := c.Begin(ctx, txOptions)
+	t, err := c.BeginEx(ctx, txOptions)
 	if err != nil {
 		return nil, err
 	}

pgxpool/tx_test.go

@@ -16,7 +16,7 @@ func TestTxExec(t *testing.T) {
 	require.NoError(t, err)
 	defer pool.Close()
 
-	tx, err := pool.Begin(context.Background(), nil)
+	tx, err := pool.Begin(context.Background())
 	require.NoError(t, err)
 	defer tx.Rollback(context.Background())
 
@@ -30,7 +30,7 @@ func TestTxQuery(t *testing.T) {
 	require.NoError(t, err)
 	defer pool.Close()
 
-	tx, err := pool.Begin(context.Background(), nil)
+	tx, err := pool.Begin(context.Background())
 	require.NoError(t, err)
 	defer tx.Rollback(context.Background())
 
@@ -44,7 +44,7 @@ func TestTxQueryRow(t *testing.T) {
 	require.NoError(t, err)
 	defer pool.Close()
 
-	tx, err := pool.Begin(context.Background(), nil)
+	tx, err := pool.Begin(context.Background())
 	require.NoError(t, err)
 	defer tx.Rollback(context.Background())
 
@@ -58,7 +58,7 @@ func TestTxSendBatch(t *testing.T) {
 	require.NoError(t, err)
 	defer pool.Close()
 
-	tx, err := pool.Begin(context.Background(), nil)
+	tx, err := pool.Begin(context.Background())
 	require.NoError(t, err)
 	defer tx.Rollback(context.Background())
 
@@ -72,7 +72,7 @@ func TestTxCopyFrom(t *testing.T) {
 	require.NoError(t, err)
 	defer pool.Close()
 
-	tx, err := pool.Begin(context.Background(), nil)
+	tx, err := pool.Begin(context.Background())
 	require.NoError(t, err)
 	defer tx.Rollback(context.Background())
 

stdlib/sql.go

@@ -209,7 +209,7 @@ func (c *Conn) BeginTx(ctx context.Context, opts driver.TxOptions) (driver.Tx, e
 		pgxOpts.AccessMode = pgx.ReadOnly
 	}
 
-	tx, err := c.conn.Begin(ctx, &pgxOpts)
+	tx, err := c.conn.BeginEx(ctx, pgxOpts)
 	if err != nil {
 		return nil, err
 	}

tx.go

@@ -50,11 +50,7 @@ type TxOptions struct {
 	DeferrableMode TxDeferrableMode
 }
 
-func (txOptions *TxOptions) beginSQL() string {
-	if txOptions == nil {
-		return "begin"
-	}
-
+func (txOptions TxOptions) beginSQL() string {
 	buf := &bytes.Buffer{}
 	buf.WriteString("begin")
 	if txOptions.IsoLevel != "" {
@@ -78,9 +74,15 @@ var ErrTxInFailure = errors.New("tx failed")
 // it is treated as ROLLBACK.
 var ErrTxCommitRollback = errors.New("commit unexpectedly resulted in rollback")
 
-// BeginEx starts a transaction with txOptions determining the transaction mode. txOptions can be nil. Unlike
-// database/sql, the context only affects the begin command. i.e. there is no auto-rollback on context cancelation.
-func (c *Conn) Begin(ctx context.Context, txOptions *TxOptions) (*Tx, error) {
+// Begin starts a transaction. Unlike database/sql, the context only affects the begin command. i.e. there is no
+// auto-rollback on context cancelation.
+func (c *Conn) Begin(ctx context.Context) (*Tx, error) {
+	return c.BeginEx(ctx, TxOptions{})
+}
+
+// BeginEx starts a transaction with txOptions determining the transaction mode. Unlike database/sql, the context only
+// affects the begin command. i.e. there is no auto-rollback on context cancelation.
+func (c *Conn) BeginEx(ctx context.Context, txOptions TxOptions) (*Tx, error) {
 	_, err := c.Exec(ctx, txOptions.beginSQL())
 	if err != nil {
 		// begin should never fail unless there is an underlying connection issue or

tx_test.go

@@ -26,7 +26,7 @@ func TestTransactionSuccessfulCommit(t *testing.T) {
 		t.Fatalf("Failed to create table: %v", err)
 	}
 
-	tx, err := conn.Begin(context.Background(), nil)
+	tx, err := conn.Begin(context.Background())
 	if err != nil {
 		t.Fatalf("conn.Begin failed: %v", err)
 	}
@@ -68,7 +68,7 @@ func TestTxCommitWhenTxBroken(t *testing.T) {
 		t.Fatalf("Failed to create table: %v", err)
 	}
 
-	tx, err := conn.Begin(context.Background(), nil)
+	tx, err := conn.Begin(context.Background())
 	if err != nil {
 		t.Fatalf("conn.Begin failed: %v", err)
 	}
@@ -113,13 +113,13 @@ func TestTxCommitSerializationFailure(t *testing.T) {
 	}
 	defer c1.Exec(context.Background(), `drop table tx_serializable_sums`)
 
-	tx1, err := c1.Begin(context.Background(), &pgx.TxOptions{IsoLevel: pgx.Serializable})
+	tx1, err := c1.BeginEx(context.Background(), pgx.TxOptions{IsoLevel: pgx.Serializable})
 	if err != nil {
 		t.Fatalf("Begin failed: %v", err)
 	}
 	defer tx1.Rollback(context.Background())
 
-	tx2, err := c2.Begin(context.Background(), &pgx.TxOptions{IsoLevel: pgx.Serializable})
+	tx2, err := c2.BeginEx(context.Background(), pgx.TxOptions{IsoLevel: pgx.Serializable})
 	if err != nil {
 		t.Fatalf("Begin failed: %v", err)
 	}
@@ -163,7 +163,7 @@ func TestTransactionSuccessfulRollback(t *testing.T) {
 		t.Fatalf("Failed to create table: %v", err)
 	}
 
-	tx, err := conn.Begin(context.Background(), nil)
+	tx, err := conn.Begin(context.Background())
 	if err != nil {
 		t.Fatalf("conn.Begin failed: %v", err)
 	}
@@ -196,7 +196,7 @@ func TestBeginIsoLevels(t *testing.T) {
 
 	isoLevels := []pgx.TxIsoLevel{pgx.Serializable, pgx.RepeatableRead, pgx.ReadCommitted, pgx.ReadUncommitted}
 	for _, iso := range isoLevels {
-		tx, err := conn.Begin(context.Background(), &pgx.TxOptions{IsoLevel: iso})
+		tx, err := conn.BeginEx(context.Background(), pgx.TxOptions{IsoLevel: iso})
 		if err != nil {
 			t.Fatalf("conn.Begin failed: %v", err)
 		}
@@ -220,7 +220,7 @@ func TestBeginReadOnly(t *testing.T) {
 	conn := mustConnectString(t, os.Getenv("PGX_TEST_DATABASE"))
 	defer closeConn(t, conn)
 
-	tx, err := conn.Begin(context.Background(), &pgx.TxOptions{AccessMode: pgx.ReadOnly})
+	tx, err := conn.BeginEx(context.Background(), pgx.TxOptions{AccessMode: pgx.ReadOnly})
 	if err != nil {
 		t.Fatalf("conn.Begin failed: %v", err)
 	}
@@ -238,7 +238,7 @@ func TestTxStatus(t *testing.T) {
 	conn := mustConnectString(t, os.Getenv("PGX_TEST_DATABASE"))
 	defer closeConn(t, conn)
 
-	tx, err := conn.Begin(context.Background(), nil)
+	tx, err := conn.Begin(context.Background())
 	if err != nil {
 		t.Fatal(err)
 	}
@@ -262,7 +262,7 @@ func TestTxStatusErrorInTransactions(t *testing.T) {
 	conn := mustConnectString(t, os.Getenv("PGX_TEST_DATABASE"))
 	defer closeConn(t, conn)
 
-	tx, err := conn.Begin(context.Background(), nil)
+	tx, err := conn.Begin(context.Background())
 	if err != nil {
 		t.Fatal(err)
 	}
@@ -309,7 +309,7 @@ func TestTxErr(t *testing.T) {
 	conn := mustConnectString(t, os.Getenv("PGX_TEST_DATABASE"))
 	defer closeConn(t, conn)
 
-	tx, err := conn.Begin(context.Background(), nil)
+	tx, err := conn.Begin(context.Background())
 	if err != nil {
 		t.Fatal(err)
 	}