func (q *queryImpl) Order(prop string) ds.Query {
col := ds.IndexColumn{}
return q.checkMutateClone(
func() error {
// check that first order == first inequality.
// if order is an equality already, ignore it
col.Property = strings.TrimSpace(prop)
if strings.HasPrefix(prop, "-") {
col.Direction = ds.DESCENDING
col.Property = strings.TrimSpace(prop[1:])
} else if strings.HasPrefix(prop, "+") {
return fmt.Errorf("datastore: invalid order: %q", prop)
}
if len(col.Property) == 0 {
return errors.New("datastore: empty order")
}
if len(q.order) == 0 && q.ineqFilter.prop != "" && q.ineqFilter.prop != col.Property {
return fmt.Errorf(
"first sort order must match inequality filter: %q v %q",
prop, q.ineqFilter.prop)
}
if q.kind == "" && (col.Property != "__key__" || col.Direction != ds.ASCENDING) {
return fmt.Errorf("invalid order for kindless query: %#v", col)
}
return nil
},
func(q *queryImpl) {
if _, ok := q.eqFilters[col.Property]; ok {
// skip it if it's an equality filter
// https://cloud.google.com/appengine/docs/go/datastore/queries#sort_orders_are_ignored_on_properties_with_equality_filters
return
}
for _, order := range q.order {
if order.Property == col.Property {
// can't sort by the same order twice
return
}
}
q.order = append(q.order, col)
})
}
func curs(pairs ...interface{}) queryCursor {
if len(pairs)%2 != 0 {
panic("curs() takes only even pairs")
}
pre := &bytes.Buffer{}
cmpbin.WriteUint(pre, uint64(len(pairs)/2))
post := serialize.Invertible(&bytes.Buffer{})
for i := 0; i < len(pairs); i += 2 {
k, v := pairs[i].(string), pairs[i+1]
col := dsS.IndexColumn{Property: k}
post.SetInvert(false)
if k[0] == '-' {
post.SetInvert(false)
col.Property = k[1:]
col.Direction = dsS.DESCENDING
}
serialize.WriteIndexColumn(pre, col)
serialize.WriteProperty(post, serialize.WithoutContext, prop(v))
}
return queryCursor(bjoin(pre.Bytes(), post.Bytes()))
}