Add support for OF in row lock clauses

This adds support for statements such as `SELECT ... FOR UPDATE OF table NOWAIT` where `OF table`
could not be specified previously. Fixes #285.

internal/jet/select_lock.go

@@ -4,12 +4,14 @@ package jet
 type RowLock interface {
 	Serializer
 
+	OF(...Table) RowLock
 	NOWAIT() RowLock
 	SKIP_LOCKED() RowLock
 }
 
 type selectLockImpl struct {
 	lockStrength       string
+	of                 []Table
 	noWait, skipLocked bool
 }
 
@@ -20,10 +22,15 @@ func NewRowLock(name string) func() RowLock {
 	}
 }
 
-func newSelectLock(lockStrength string) RowLock {
+func newSelectLock(lockStrength string) *selectLockImpl {
 	return &selectLockImpl{lockStrength: lockStrength}
 }
 
+func (s *selectLockImpl) OF(tables ...Table) RowLock {
+	s.of = tables
+	return s
+}
+
 func (s *selectLockImpl) NOWAIT() RowLock {
 	s.noWait = true
 	return s
@@ -37,6 +44,23 @@ func (s *selectLockImpl) SKIP_LOCKED() RowLock {
 func (s *selectLockImpl) serialize(statement StatementType, out *SQLBuilder, options ...SerializeOption) {
 	out.WriteString(s.lockStrength)
 
+	if len(s.of) > 0 {
+		out.WriteString("OF")
+
+		for i, of := range s.of {
+			if i > 0 {
+				out.WriteString(", ")
+			}
+
+			table := of.Alias()
+			if table == "" {
+				table = of.TableName()
+			}
+
+			out.WriteIdentifier(table)
+		}
+	}
+
 	if s.noWait {
 		out.WriteString("NOWAIT")
 	}