Introduce ScanColumn and NamedScanColumn as the less ugly way (i can see) to known if

a column is null.

sqlite.go

@@ -469,12 +469,12 @@ func (s *Stmt) NamedScan(args ...interface{}) os.Error {
 		if !ok {
 			return os.NewError("non-string field name field")
 		}
-		index, err := s.fieldIndex(name) // How to look up only once for one statement ?
+		index, err := s.ColumnIndex(name) // How to look up only once for one statement ?
 		if err != nil {
 			return err
 		}
 		ptr := args[i+1]
-		_, err = s.scanField(index, ptr, false)
+		_, err = s.ScanColumn(index, ptr, false)
 		if err != nil {
 			return err
 		}
@@ -493,7 +493,7 @@ func (s *Stmt) Scan(args ...interface{}) os.Error {
 	}
 
 	for i, v := range args {
-		_, err := s.scanField(i, v, false)
+		_, err := s.ScanColumn(i, v, false)
 		if err != nil {
 			return err
 		}
@@ -506,7 +506,10 @@ func (s *Stmt) SQL() string {
 	return C.GoString(C.sqlite3_sql(s.stmt))
 }
 
-func (s *Stmt) fieldIndex(name string) (int, os.Error) {
+// Must scan all columns (but result is cached).
+// Calls sqlite3_column_count, sqlite3_column_name
+// http://sqlite.org/c3ref/column_name.html
+func (s *Stmt) ColumnIndex(name string) (int, os.Error) {
 	if s.cols == nil {
 		count := s.ColumnCount()
 		s.cols = make(map[string]int, count)
@@ -523,7 +526,23 @@ func (s *Stmt) fieldIndex(name string) (int, os.Error) {
 
 // Set nullable to false to skip NULL type test.
 // Returns true when nullable is true and field is null.
-func (s *Stmt) scanField(index int, value interface{}, nullable bool) (bool, os.Error) {
+// Calls sqlite3_column_count, sqlite3_column_name and sqlite3_column_(blob|double|int|int64|text) depending on args type.
+// http://sqlite.org/c3ref/column_blob.html
+func (s *Stmt) NamedScanColumn(name string, value interface{}, nullable bool) (bool, os.Error) {
+	index, err := s.ColumnIndex(name)
+	if err != nil {
+		return false, err
+	}
+	return s.ScanColumn(index, value, true)
+}
+
+// The leftmost column is number 0.
+// Index starts at 0.
+// Set nullable to false to skip NULL type test.
+// Returns true when nullable is true and field is null.
+// Calls sqlite3_column_(blob|double|int|int64|text) depending on args type.
+// http://sqlite.org/c3ref/column_blob.html
+func (s *Stmt) ScanColumn(index int, value interface{}, nullable bool) (bool, os.Error) {
 	var isNull bool
 	switch value := value.(type) {
 	case *string:

sqlite_test.go

@@ -216,10 +216,10 @@ func TestInsertWithStatement(t *testing.T) {
 		t.Errorf("column name error: %s <> 'int_num'", secondColumnName)
 	}
 
-	var fnum float64
-	var inum int64
-	var sstr string
 	if ok, _ := rs.Next(); ok {
+		var fnum float64
+		var inum int64
+		var sstr string
 		rs.Scan(&fnum, &inum, &sstr)
 		if fnum != 0 {
 			t.Errorf("Expected 0 <> %f\n", fnum)
@@ -376,6 +376,90 @@ func TestBlob(t *testing.T) {
 	br.Close()
 }
 
+func testScanColumn(t *testing.T) {
+	db := open(t)
+	defer db.Close()
+
+	s, err := db.Prepare("select 1, null, 0")
+	if err != nil {
+		t.Fatalf("prepare error: %s", err)
+	}
+	defer s.Finalize()
+	if ok, err := s.Next(); !ok {
+		if err != nil {
+			t.Fatalf("error preparing count: %s", err)
+		}
+		t.Fatal("no result for count")
+	}
+	var i1, i2, i3 int
+	null, err := s.ScanColumn(0, &i1, true)
+	if err != nil {
+		t.Errorf("scan error: %s\n", err)
+	} else if null {
+		t.Errorf("Expected not null value")
+	} else if i1 != 1 {
+		t.Errorf("Expected 1 <> %d\n", i1)
+	}
+	null, err = s.ScanColumn(1, &i2, true)
+	if err != nil {
+		t.Errorf("scan error: %s\n", err)
+	} else if !null {
+		t.Errorf("Expected null value")
+	} else if i2 != 0 {
+		t.Errorf("Expected 0 <> %d\n", i2)
+	}
+	null, err = s.ScanColumn(2, &i3, true)
+	if err != nil {
+		t.Errorf("scan error: %s\n", err)
+	} else if null {
+		t.Errorf("Expected not null value")
+	} else if i3 != 0 {
+		t.Errorf("Expected 0 <> %d\n", i3)
+	}
+}
+
+func testNamedScanColumn(t *testing.T) {
+	db := open(t)
+	defer db.Close()
+
+	s, err := db.Prepare("select 1 as i1, null as i2, 0 as i3")
+	if err != nil {
+		t.Fatalf("prepare error: %s", err)
+	}
+	defer s.Finalize()
+	if ok, err := s.Next(); !ok {
+		if err != nil {
+			t.Fatalf("error preparing count: %s", err)
+		}
+		t.Fatal("no result for count")
+	}
+	var i1, i2, i3 int
+	null, err := s.NamedScanColumn("i1", &i1, true)
+	if err != nil {
+		t.Errorf("scan error: %s\n", err)
+	} else if null {
+		t.Errorf("Expected not null value")
+	} else if i1 != 1 {
+		t.Errorf("Expected 1 <> %d\n", i1)
+	}
+	null, err = s.NamedScanColumn("i2", &i2, true)
+	if err != nil {
+		t.Errorf("scan error: %s\n", err)
+	} else if !null {
+		t.Errorf("Expected null value")
+	} else if i2 != 0 {
+		t.Errorf("Expected 0 <> %d\n", i2)
+	}
+	null, err = s.NamedScanColumn("i3", &i3, true)
+	if err != nil {
+		t.Errorf("scan error: %s\n", err)
+	} else if null {
+		t.Errorf("Expected not null value")
+	} else if i3 != 0 {
+		t.Errorf("Expected 0 <> %d\n", i3)
+	}
+}
+
 func BenchmarkScan(b *testing.B) {
 	b.StopTimer()
 	db, _ := Open("")

trace.go

@@ -223,9 +223,9 @@ func (c *Conn) ProgressHandler(f ProgressHandler, freq int, arg interface{}) {
 type StmtStatus int
 
 const (
-	STMTSTATUS_FULLSCAN_STEP  StmtStatus = C.SQLITE_STMTSTATUS_FULLSCAN_STEP
-	STMTSTATUS_SORT StmtStatus = C.SQLITE_STMTSTATUS_SORT
-	STMTSTATUS_AUTOINDEX StmtStatus = C.SQLITE_STMTSTATUS_AUTOINDEX
+	STMTSTATUS_FULLSCAN_STEP StmtStatus = C.SQLITE_STMTSTATUS_FULLSCAN_STEP
+	STMTSTATUS_SORT          StmtStatus = C.SQLITE_STMTSTATUS_SORT
+	STMTSTATUS_AUTOINDEX     StmtStatus = C.SQLITE_STMTSTATUS_AUTOINDEX
 )
 
 // Calls http://sqlite.org/c3ref/stmt_status.html