func (p *UnionPlan) fetchSrc(ctx context.Context, i int, t memkv.Temp) error {
src := p.Srcs[i+1]
distinct := p.Distincts[i]
// Use the ResultFields of the first select statement as the final ResultFields
rfs := p.Srcs[0].GetFields()
if len(src.GetFields()) != len(rfs) {
return errors.New("The used SELECT statements have a different number of columns")
}
for {
row, err := src.Next(ctx)
if row == nil || err != nil {
return errors.Trace(err)
}
srcRfs := src.GetFields()
for i := range row.Data {
// The column value should be casted as the same type of the first select statement in corresponding position
srcRf := srcRfs[i]
rf := rfs[i]
/*
* The lengths of the columns in the UNION result take into account the values retrieved by all of the SELECT statements
* SELECT REPEAT('a',1) UNION SELECT REPEAT('b',10);
* +---------------+
* | REPEAT('a',1) |
* +---------------+
* | a |
* | bbbbbbbbbb |
* +---------------+
*/
if srcRf.Flen > rf.Col.Flen {
rf.Col.Flen = srcRf.Col.Flen
}
row.Data[i], err = types.Convert(row.Data[i], &rf.Col.FieldType)
if err != nil {
return errors.Trace(err)
}
}
if distinct {
// distinct union, check duplicate
v, getErr := t.Get(row.Data)
if getErr != nil {
return errors.Trace(getErr)
}
if len(v) > 0 {
// Find duplicate, ignore it
continue
}
}
p.rows = append(p.rows, row)
if err := t.Set(row.Data, []interface{}{true}); err != nil {
return errors.Trace(err)
}
}
}
func (p *UnionPlan) fetchSrc(ctx context.Context, i int, t memkv.Temp) error {
src := p.Srcs[i+1]
distinct := p.Distincts[i]
rfs := p.GetFields()
if len(src.GetFields()) != len(rfs) {
return errors.New("The used SELECT statements have a different number of columns")
}
for {
row, err := src.Next(ctx)
if row == nil || err != nil {
return errors.Trace(err)
}
srcRfs := src.GetFields()
for i := range row.Data {
// The column value should be casted as the same type of the first select statement in corresponding position
srcRf := srcRfs[i]
rf := rfs[i]
/*
* The lengths of the columns in the UNION result take into account the values retrieved by all of the SELECT statements
* SELECT REPEAT('a',1) UNION SELECT REPEAT('b',10);
* +---------------+
* | REPEAT('a',1) |
* +---------------+
* | a |
* | bbbbbbbbbb |
* +---------------+
*/
if srcRf.Flen > rf.Col.Flen {
rf.Col.Flen = srcRf.Col.Flen
}
if rf.Col.FieldType.Tp > 0 {
row.Data[i], err = types.Convert(row.Data[i], &rf.Col.FieldType)
} else {
// First select result doesn't contain enough type information, e,g, select null union select 1.
// We cannot get the proper data type for select null.
// Now we just use the first correct return data types with following select.
// TODO: Try to merge all data types for all select like select null union select 1 union select "abc"
if tp := srcRf.Col.FieldType.Tp; tp > 0 {
rf.Col.FieldType.Tp = tp
}
}
if err != nil {
return errors.Trace(err)
}
}
if distinct {
// distinct union, check duplicate
v, getErr := t.Get(row.Data)
if getErr != nil {
return errors.Trace(getErr)
}
if len(v) > 0 {
// Find duplicate, ignore it
continue
}
}
p.rows = append(p.rows, row)
if err := t.Set(row.Data, []interface{}{true}); err != nil {
return errors.Trace(err)
}
}
}