// UpdateAggFields adds aggregate function resultfield to select result field list.
func (s *SelectList) UpdateAggFields(expr expression.Expression, tableFields []*field.ResultField) (expression.Expression, error) {
// For aggregate function, the name can be in table or select list.
names := expressions.MentionedColumns(expr)
for _, name := range names {
if field.ContainFieldName(name, tableFields, field.DefaultFieldFlag) {
continue
}
if field.ContainFieldName(name, s.ResultFields, field.DefaultFieldFlag) {
continue
}
return nil, errors.Errorf("Unknown column '%s'", name)
}
// We must add aggregate function to hidden select list
// and use a position expression to fetch its value later.
exprName := expr.String()
if !field.ContainFieldName(exprName, s.ResultFields, field.CheckFieldFlag) {
f := &field.Field{Expr: expr, Name: exprName}
resultField := &field.ResultField{Name: exprName}
s.AddField(f, resultField)
return &expressions.Position{N: len(s.Fields), Name: exprName}, nil
}
return nil, nil
}
// CheckAndUpdateSelectList checks having fields validity and set hidden fields to selectList.
func (r *HavingRset) CheckAndUpdateSelectList(selectList *plans.SelectList, groupBy []expression.Expression, tableFields []*field.ResultField) error {
if err := expressions.CheckOneColumn(r.Expr); err != nil {
return errors.Trace(err)
}
if expressions.ContainAggregateFunc(r.Expr) {
expr, err := selectList.UpdateAggFields(r.Expr, tableFields)
if err != nil {
return errors.Errorf("%s in 'having clause'", err.Error())
}
r.Expr = expr
} else {
// having can only contain group by column and select list, e.g,
// `select c1 from t group by c2 having c3 > 0` is invalid,
// because c3 is not in group by and select list.
names := expressions.MentionedColumns(r.Expr)
for _, name := range names {
found := false
// check name whether in select list.
// notice that `select c1 as c2 from t group by c1, c2, c3 having c2 > c3`,
// will use t.c2 not t.c1 here.
if field.ContainFieldName(name, selectList.ResultFields, field.OrgFieldNameFlag) {
continue
}
if field.ContainFieldName(name, selectList.ResultFields, field.FieldNameFlag) {
if field.ContainFieldName(name, tableFields, field.OrgFieldNameFlag) {
selectList.CloneHiddenField(name, tableFields)
}
continue
}
// check name whether in group by.
// group by must only have column name, e.g,
// `select c1 from t group by c2 having c2 > 0` is valid,
// but `select c1 from t group by c2 + 1 having c2 > 0` is invalid.
for _, by := range groupBy {
if !field.CheckFieldsEqual(name, by.String()) {
continue
}
// if name is not in table fields, it will get an unknown field error in GroupByRset,
// so no need to check return value.
selectList.CloneHiddenField(name, tableFields)
found = true
break
}
if !found {
return errors.Errorf("Unknown column '%s' in 'having clause'", name)
}
}
}
return nil
}
// CheckAndUpdateSelectList checks order by fields validity and set hidden fields to selectList.
func (r *OrderByRset) CheckAndUpdateSelectList(selectList *plans.SelectList, tableFields []*field.ResultField) error {
for i, v := range r.By {
if expressions.ContainAggregateFunc(v.Expr) {
expr, err := selectList.UpdateAggFields(v.Expr, tableFields)
if err != nil {
return errors.Errorf("%s in 'order clause'", err.Error())
}
r.By[i].Expr = expr
} else {
names := expressions.MentionedColumns(v.Expr)
for _, name := range names {
// try to find in select list
// TODO: mysql has confused result for this, see #555.
// now we use select list then order by, later we should make it easier.
if field.ContainFieldName(name, selectList.ResultFields, field.CheckFieldFlag) {
// check ambiguous fields, like `select c1 as c2, c2 from t order by c2`.
if err := field.CheckAmbiguousField(name, selectList.ResultFields, field.DefaultFieldFlag); err != nil {
return errors.Errorf("Column '%s' in order statement is ambiguous", name)
}
continue
}
if !selectList.CloneHiddenField(name, tableFields) {
return errors.Errorf("Unknown column '%s' in 'order clause'", name)
}
}
}
}
return nil
}
// CloneHiddenField checks and clones field and result field from table fields,
// and adds them to hidden field of select list.
func (s *SelectList) CloneHiddenField(name string, tableFields []*field.ResultField) bool {
// Check and add hidden field.
if field.ContainFieldName(name, tableFields, field.CheckFieldFlag) {
resultField, _ := field.CloneFieldByName(name, tableFields, field.CheckFieldFlag)
f := &field.Field{
Expr: &expression.Ident{
CIStr: resultField.ColumnInfo.Name,
},
}
s.AddField(f, resultField)
return true
}
return false
}
// CheckAndUpdateSelectList checks order by fields validity and set hidden fields to selectList.
func (r *OrderByRset) CheckAndUpdateSelectList(selectList *plans.SelectList, tableFields []*field.ResultField) error {
for i, v := range r.By {
if expression.ContainAggregateFunc(v.Expr) {
expr, err := selectList.UpdateAggFields(v.Expr, tableFields)
if err != nil {
return errors.Errorf("%s in 'order clause'", err.Error())
}
r.By[i].Expr = expr
} else {
if _, err := selectList.CheckReferAmbiguous(v.Expr); err != nil {
return errors.Errorf("Column '%s' in order statement is ambiguous", v.Expr)
}
// TODO: check more ambiguous case
// Order by ambiguous rule:
// select c1 as a, c2 as a from t order by a is ambiguous
// select c1 as a, c2 as a from t order by a + 1 is ambiguous
// select c1 as c2, c2 from t order by c2 is ambiguous
// select c1 as c2, c2 from t order by c2 + 1 is ambiguous
// TODO: use vistor to refactor all and combine following plan check.
names := expression.MentionedColumns(v.Expr)
for _, name := range names {
// try to find in select list
// TODO: mysql has confused result for this, see #555.
// now we use select list then order by, later we should make it easier.
if field.ContainFieldName(name, selectList.ResultFields, field.CheckFieldFlag) {
continue
}
if !selectList.CloneHiddenField(name, tableFields) {
return errors.Errorf("Unknown column '%s' in 'order clause'", name)
}
}
}
}
return nil
}
// Plan gets GroupByDefaultPlan.
func (r *GroupByRset) Plan(ctx context.Context) (plan.Plan, error) {
fields := r.SelectList.Fields
resultfields := r.SelectList.ResultFields
srcFields := r.Src.GetFields()
r.SelectList.AggFields = GetAggFields(fields)
aggFields := r.SelectList.AggFields
for i, e := range r.By {
if v, ok := e.(expressions.Value); ok {
var position int
switch u := v.Val.(type) {
case int64:
position = int(u)
case uint64:
position = int(u)
default:
continue
}
if position < 1 || position > len(fields) {
return nil, errors.Errorf("Unknown column '%d' in 'group statement'", position)
}
index := position - 1
if _, ok := aggFields[index]; ok {
return nil, errors.Errorf("Can't group on '%s'", fields[index].Name)
}
// use Position expression for the associated field.
r.By[i] = &expressions.Position{N: position}
} else {
names := expressions.MentionedColumns(e)
for _, name := range names {
if field.ContainFieldName(name, srcFields, field.DefaultFieldFlag) {
// check whether column is qualified, like `select t.c1 c1, t.c2 from t group by t.c1, t.c2`
// no need to check ambiguous field.
if expressions.IsQualified(name) {
continue
}
// check ambiguous fields, like `select c1 as c2, c2 from t group by c2`.
if err := field.CheckAmbiguousField(name, resultfields, field.DefaultFieldFlag); err == nil {
continue
}
}
// check reference to group function name
indices := field.GetFieldIndex(name, fields[0:r.SelectList.HiddenFieldOffset], field.CheckFieldFlag)
if len(indices) > 1 {
// check ambiguous fields, like `select c1 as a, c2 as a from t group by a`,
// notice that `select c2 as c2, c2 as c2 from t group by c2;` is valid.
if r.HasAmbiguousField(indices, fields[0:r.SelectList.HiddenFieldOffset]) {
return nil, errors.Errorf("Column '%s' in group statement is ambiguous", name)
}
} else if len(indices) == 1 {
// check reference to aggregate function, like `select c1, count(c1) as b from t group by b + 1`.
index := indices[0]
if _, ok := aggFields[index]; ok {
return nil, errors.Errorf("Reference '%s' not supported (reference to group function)", name)
}
}
}
// group by should be an expression, a qualified field name or a select field position,
// but can not contain any aggregate function.
if e := r.By[i]; expressions.ContainAggregateFunc(e) {
return nil, errors.Errorf("group by cannot contain aggregate function %s", e.String())
}
}
}
return &plans.GroupByDefaultPlan{By: r.By, Src: r.Src, SelectList: r.SelectList}, nil
}