Add support for sql.TxOptions

Author: thatguystone

conn.go

@@ -506,13 +506,17 @@ func (cn *conn) checkIsInTransaction(intxn bool) {
 }
 
 func (cn *conn) Begin() (_ driver.Tx, err error) {
+	return cn.begin("")
+}
+
+func (cn *conn) begin(mode string) (_ driver.Tx, err error) {
 	if cn.bad {
 		return nil, driver.ErrBadConn
 	}
 	defer cn.errRecover(&err)
 
 	cn.checkIsInTransaction(false)
-	_, commandTag, err := cn.simpleExec("BEGIN")
+	_, commandTag, err := cn.simpleExec("BEGIN" + mode)
 	if err != nil {
 		return nil, err
 	}

conn_go18.go

@@ -4,8 +4,9 @@ package pq
 
 import (
 	"context"
+	"database/sql"
 	"database/sql/driver"
-	"errors"
+	"fmt"
 	"io"
 	"io/ioutil"
 )
@@ -44,13 +45,30 @@ func (cn *conn) ExecContext(ctx context.Context, query string, args []driver.Nam
 
 // Implement the "ConnBeginTx" interface
 func (cn *conn) BeginTx(ctx context.Context, opts driver.TxOptions) (driver.Tx, error) {
-	if opts.Isolation != 0 {
-		return nil, errors.New("isolation levels not supported")
+	var mode string
+
+	switch sql.IsolationLevel(opts.Isolation) {
+	case sql.LevelDefault:
+		// Don't touch mode: use the server's default
+	case sql.LevelReadUncommitted:
+		mode = " ISOLATION LEVEL READ UNCOMMITTED"
+	case sql.LevelReadCommitted:
+		mode = " ISOLATION LEVEL READ COMMITTED"
+	case sql.LevelRepeatableRead:
+		mode = " ISOLATION LEVEL REPEATABLE READ"
+	case sql.LevelSerializable:
+		mode = " ISOLATION LEVEL SERIALIZABLE"
+	default:
+		return nil, fmt.Errorf("pq: isolation level not supported: %d", opts.Isolation)
 	}
+
 	if opts.ReadOnly {
-		return nil, errors.New("read-only transactions not supported")
+		mode += " READ ONLY"
+	} else {
+		mode += " READ WRITE"
 	}
-	tx, err := cn.Begin()
+
+	tx, err := cn.begin(mode)
 	if err != nil {
 		return nil, err
 	}

go18_test.go

@@ -6,6 +6,7 @@ import (
 	"context"
 	"database/sql"
 	"runtime"
+	"strings"
 	"testing"
 	"time"
 )
@@ -239,3 +240,80 @@ func TestContextCancelBegin(t *testing.T) {
 		}
 	}
 }
+
+func TestTxOptions(t *testing.T) {
+	db := openTestConn(t)
+	defer db.Close()
+	ctx := context.Background()
+
+	tests := []struct {
+		level     sql.IsolationLevel
+		isolation string
+	}{
+		{
+			level:     sql.LevelDefault,
+			isolation: "",
+		},
+		{
+			level:     sql.LevelReadUncommitted,
+			isolation: "read uncommitted",
+		},
+		{
+			level:     sql.LevelReadCommitted,
+			isolation: "read committed",
+		},
+		{
+			level:     sql.LevelRepeatableRead,
+			isolation: "repeatable read",
+		},
+		{
+			level:     sql.LevelSerializable,
+			isolation: "serializable",
+		},
+	}
+
+	for _, test := range tests {
+		for _, ro := range []bool{true, false} {
+			tx, err := db.BeginTx(ctx, &sql.TxOptions{
+				Isolation: test.level,
+				ReadOnly:  ro,
+			})
+			if err != nil {
+				t.Fatal(err)
+			}
+
+			var isolation string
+			err = tx.QueryRow("select current_setting('transaction_isolation')").Scan(&isolation)
+			if err != nil {
+				t.Fatal(err)
+			}
+
+			if test.isolation != "" && isolation != test.isolation {
+				t.Errorf("wrong isolation level: %s != %s", isolation, test.isolation)
+			}
+
+			var isRO string
+			err = tx.QueryRow("select current_setting('transaction_read_only')").Scan(&isRO)
+			if err != nil {
+				t.Fatal(err)
+			}
+
+			if ro != (isRO == "on") {
+				t.Errorf("read/[write,only] not set: %t != %s for level %s",
+					ro, isRO, test.isolation)
+			}
+
+			tx.Rollback()
+		}
+	}
+
+	_, err := db.BeginTx(ctx, &sql.TxOptions{
+		Isolation: sql.LevelLinearizable,
+	})
+	if err == nil {
+		t.Fatal("expected LevelLinearizable to fail")
+	}
+	if !strings.Contains(err.Error(), "isolation level not supported") {
+		t.Errorf("Expected error to mention isolation level, got %q", err)
+	}
+}