Add GroupBy to QuerySeter

Adds support for GroupBy to QuerySeter SELECT operations.

@@ -800,6 +800,7 @@ func (d *dbBase) ReadBatch(q dbQuerier, qs *querySet, mi *modelInfo, cond *Condi
 	tables.parseRelated(qs.related, qs.relDepth)
 
 	where, args := tables.getCondSql(cond, false, tz)
+	groupBy := tables.getGroupSql(qs.groups)
 	orderBy := tables.getOrderSql(qs.orders)
 	limit := tables.getLimitSql(mi, offset, rlimit)
 	join := tables.getJoinSql()
@@ -812,7 +813,7 @@ func (d *dbBase) ReadBatch(q dbQuerier, qs *querySet, mi *modelInfo, cond *Condi
 		}
 	}
 
-	query := fmt.Sprintf("SELECT %s FROM %s%s%s T0 %s%s%s%s", sels, Q, mi.table, Q, join, where, orderBy, limit)
+	query := fmt.Sprintf("SELECT %s FROM %s%s%s T0 %s%s%s%s%s", sels, Q, mi.table, Q, join, where, groupBy, orderBy, limit)
 
 	d.ins.ReplaceMarks(&query)
 
@@ -936,12 +937,13 @@ func (d *dbBase) Count(q dbQuerier, qs *querySet, mi *modelInfo, cond *Condition
 	tables.parseRelated(qs.related, qs.relDepth)
 
 	where, args := tables.getCondSql(cond, false, tz)
+	groupBy := tables.getGroupSql(qs.groups)
 	tables.getOrderSql(qs.orders)
 	join := tables.getJoinSql()
 
 	Q := d.ins.TableQuote()
 
-	query := fmt.Sprintf("SELECT COUNT(*) FROM %s%s%s T0 %s%s", Q, mi.table, Q, join, where)
+	query := fmt.Sprintf("SELECT COUNT(*) FROM %s%s%s T0 %s%s%s", Q, mi.table, Q, join, where, groupBy)
 
 	d.ins.ReplaceMarks(&query)
 
@@ -1442,13 +1444,14 @@ func (d *dbBase) ReadValues(q dbQuerier, qs *querySet, mi *modelInfo, cond *Cond
 	}
 
 	where, args := tables.getCondSql(cond, false, tz)
+	groupBy := tables.getGroupSql(qs.groups)
 	orderBy := tables.getOrderSql(qs.orders)
 	limit := tables.getLimitSql(mi, qs.offset, qs.limit)
 	join := tables.getJoinSql()
 
 	sels := strings.Join(cols, ", ")
 
-	query := fmt.Sprintf("SELECT %s FROM %s%s%s T0 %s%s%s%s", sels, Q, mi.table, Q, join, where, orderBy, limit)
+	query := fmt.Sprintf("SELECT %s FROM %s%s%s T0 %s%s%s%s%s", sels, Q, mi.table, Q, join, where, groupBy, orderBy, limit)
 
 	d.ins.ReplaceMarks(&query)
 

@@ -390,6 +390,30 @@ func (t *dbTables) getCondSql(cond *Condition, sub bool, tz *time.Location) (whe
 	return
 }
 
+// generate group sql.
+func (t *dbTables) getGroupSql(groups []string) (groupSql string) {
+	if len(groups) == 0 {
+		return
+	}
+
+	Q := t.base.TableQuote()
+
+	groupSqls := make([]string, 0, len(groups))
+	for _, group := range groups {
+		exprs := strings.Split(group, ExprSep)
+
+		index, _, fi, suc := t.parseExprs(t.mi, exprs)
+		if suc == false {
+			panic(fmt.Errorf("unknown field/column name `%s`", strings.Join(exprs, ExprSep)))
+		}
+
+		groupSqls = append(groupSqls, fmt.Sprintf("%s.%s%s%s", index, Q, fi.column, Q))
+	}
+
+	groupSql = fmt.Sprintf("GROUP BY %s ", strings.Join(groupSqls, ", "))
+	return
+}
+
 // generate order sql.
 func (t *dbTables) getOrderSql(orders []string) (orderSql string) {
 	if len(orders) == 0 {

@@ -60,6 +60,7 @@ type querySet struct {
 	relDepth int
 	limit    int64
 	offset   int64
+	groups   []string
 	orders   []string
 	orm      *orm
 }
@@ -105,6 +106,12 @@ func (o querySet) Offset(offset interface{}) QuerySeter {
 	return &o
 }
 
+// add GROUP expression.
+func (o querySet) GroupBy(exprs ...string) QuerySeter {
+	o.groups = exprs
+	return &o
+}
+
 // add ORDER expression.
 // "column" means ASC, "-column" means DESC.
 func (o querySet) OrderBy(exprs ...string) QuerySeter {

@@ -845,6 +845,27 @@ func TestOffset(t *testing.T) {
 	throwFail(t, AssertIs(num, 2))
 }
 
+func TestGroupBy(t *testing.T) {
+	var users []*User
+	var maps []Params
+	qs := dORM.QueryTable("user")
+	num, err := qs.GroupBy("is_staff").Filter("user_name", "nobody").Count()
+	throwFail(t, err)
+	throwFail(t, AssertIs(num, 1))
+
+	num, err = qs.GroupBy("is_staff").Count()
+	throwFail(t, err)
+	throwFail(t, AssertIs(num, 2))
+
+	num, err = qs.GroupBy("is_staff").Values(&maps)
+	throwFail(t, err)
+	throwFail(t, AssertIs(num, 2))
+
+	num, err = qs.GroupBy("profile__age").Filter("user_name", "astaxie").All(&users)
+	throwFail(t, err)
+	throwFail(t, AssertIs(num, 1))
+}
+
 func TestOrderBy(t *testing.T) {
 	qs := dORM.QueryTable("user")
 	num, err := qs.OrderBy("-status").Filter("user_name", "nobody").Count()

@@ -67,6 +67,7 @@ type QuerySeter interface {
 	SetCond(*Condition) QuerySeter
 	Limit(interface{}, ...interface{}) QuerySeter
 	Offset(interface{}) QuerySeter
+	GroupBy(...string) QuerySeter
 	OrderBy(...string) QuerySeter
 	RelatedSel(...interface{}) QuerySeter
 	Count() (int64, error)