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.

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())