Support count with cols (#1595)

Support count with cols

Reviewed-on: https://gitea.com/xorm/xorm/pulls/1595

interface.go

@@ -59,6 +59,7 @@ type Interface interface {
 	QueryString(sqlOrArgs ...interface{}) ([]map[string]string, error)
 	Rows(bean interface{}) (*Rows, error)
 	SetExpr(string, interface{}) *Session
+	Select(string) *Session
 	SQL(interface{}, ...interface{}) *Session
 	Sum(bean interface{}, colName string) (float64, error)
 	SumInt(bean interface{}, colName string) (int64, error)

internal/statements/query.go

@@ -153,6 +153,7 @@ func (statement *Statement) GenGetSQL(bean interface{}) (string, []interface{},
 	return sqlStr, append(statement.joinArgs, condArgs...), nil
 }
 
+// GenCountSQL generates the SQL for counting
 func (statement *Statement) GenCountSQL(beans ...interface{}) (string, []interface{}, error) {
 	if statement.RawSQL != "" {
 		return statement.GenRawSQL(), statement.RawParams, nil
@@ -171,6 +172,8 @@ func (statement *Statement) GenCountSQL(beans ...interface{}) (string, []interfa
 	if len(selectSQL) <= 0 {
 		if statement.IsDistinct {
 			selectSQL = fmt.Sprintf("count(DISTINCT %s)", statement.ColumnStr())
+		} else if statement.ColumnStr() != "" {
+			selectSQL = fmt.Sprintf("count(%s)", statement.ColumnStr())
 		} else {
 			selectSQL = "count(*)"
 		}

session_stats_test.go

@@ -274,3 +274,27 @@ func TestWithTableName(t *testing.T) {
 	assert.NoError(t, err)
 	assert.EqualValues(t, 2, total)
 }
+
+func TestCountWithSelectCols(t *testing.T) {
+	assert.NoError(t, prepareEngine())
+
+	assertSync(t, new(CountWithTableName))
+
+	_, err := testEngine.Insert(&CountWithTableName{
+		Name: "orderby",
+	})
+	assert.NoError(t, err)
+
+	_, err = testEngine.Insert(CountWithTableName{
+		Name: "limit",
+	})
+	assert.NoError(t, err)
+
+	total, err := testEngine.Cols("id").Count(new(CountWithTableName))
+	assert.NoError(t, err)
+	assert.EqualValues(t, 2, total)
+
+	total, err = testEngine.Select("count(id)").Count(CountWithTableName{})
+	assert.NoError(t, err)
+	assert.EqualValues(t, 2, total)
+}