func curs(pairs ...interface{}) queryCursor {
if len(pairs)%2 != 0 {
panic("curs() takes only even pairs")
}
pre := &bytes.Buffer{}
if _, err := cmpbin.WriteUint(pre, uint64(len(pairs)/2)); err != nil {
panic(err)
}
post := serialize.Invertible(&bytes.Buffer{})
for i := 0; i < len(pairs); i += 2 {
k, v := pairs[i].(string), pairs[i+1]
col, err := dstore.ParseIndexColumn(k)
if err != nil {
panic(err)
}
post.SetInvert(col.Descending)
if err := serialize.WriteIndexColumn(pre, col); err != nil {
panic(err)
}
if err := serialize.WriteProperty(post, serialize.WithoutContext, prop(v)); err != nil {
panic(err)
}
}
return queryCursor(serialize.Join(pre.Bytes(), post.Bytes()))
}
func executeQuery(fq *ds.FinalizedQuery, aid, ns string, isTxn bool, idx, head *memStore, cb ds.RawRunCB) error {
rq, err := reduce(fq, aid, ns, isTxn)
if err == ds.ErrNullQuery {
return nil
}
if err != nil {
return err
}
idxs, err := getIndexes(rq, idx)
if err == ds.ErrNullQuery {
return nil
}
if err != nil {
return err
}
strategy := pickQueryStrategy(fq, rq, cb, head)
if strategy == nil {
// e.g. the normalStrategy found that there were NO entities in the current
// namespace.
return nil
}
offset, _ := fq.Offset()
limit, hasLimit := fq.Limit()
cursorPrefix := []byte(nil)
getCursorFn := func(suffix []byte) func() (ds.Cursor, error) {
return func() (ds.Cursor, error) {
if cursorPrefix == nil {
buf := &bytes.Buffer{}
_, err := cmpbin.WriteUint(buf, uint64(len(rq.suffixFormat)))
memoryCorruption(err)
for _, col := range rq.suffixFormat {
err := serialize.WriteIndexColumn(buf, col)
memoryCorruption(err)
}
cursorPrefix = buf.Bytes()
}
// TODO(riannucci): Do we need to decrement suffix instead of increment
// if we're sorting by __key__ DESCENDING?
return queryCursor(serialize.Join(cursorPrefix, increment(suffix))), nil
}
}
return multiIterate(idxs, func(suffix []byte) error {
if offset > 0 {
offset--
return nil
}
if hasLimit {
if limit <= 0 {
return ds.Stop
}
limit--
}
rawData, decodedProps := parseSuffix(aid, ns, rq.suffixFormat, suffix, -1)
keyProp := decodedProps[len(decodedProps)-1]
if keyProp.Type() != ds.PTKey {
impossible(fmt.Errorf("decoded index row doesn't end with a Key: %#v", keyProp))
}
return strategy.handle(
rawData, decodedProps, keyProp.Value().(*ds.Key),
getCursorFn(suffix))
})
}