// processSort does either a coarse or a fine sort.
func processSort(ts *task.Sort) (*task.SortResult, error) {
attr := ts.Attr
x.AssertTruef(ts.Count > 0,
("We do not yet support negative or infinite count with sorting: %s %d. " +
"Try flipping order and return first few elements instead."),
attr, ts.Count)
n := len(ts.UidMatrix)
out := make([]intersectedList, n)
for i := 0; i < n; i++ {
// offsets[i] is the offset for i-th posting list. It gets decremented as we
// iterate over buckets.
out[i].offset = int(ts.Offset)
out[i].ulist = &task.List{Uids: []uint64{}}
}
// Iterate over every bucket in TokensTable.
t := posting.GetTokensTable(attr)
var token string
if ts.Desc {
token = t.GetLast()
} else {
token = t.GetFirst()
}
BUCKETS:
for len(token) > 0 {
err := intersectBucket(ts, attr, token, out)
switch err {
case errDone:
break BUCKETS
case errContinue:
// Continue iterating over tokens.
default:
return &emptySortResult, err
}
if ts.Desc {
token = t.GetPrev(token)
} else {
token = t.GetNext(token)
}
}
r := new(task.SortResult)
for _, il := range out {
r.UidMatrix = append(r.UidMatrix, il.ulist)
}
return r, nil
}
// getInequalityTokens gets tokens geq / leq compared to given token.
func getInequalityTokens(attr, ineqValueToken string, geq bool) ([]string, error) {
tt := posting.GetTokensTable(attr)
if tt == nil {
return nil, x.Errorf("Attribute %s is not indexed", attr)
}
var s string
if geq {
s = tt.GetNextOrEqual(ineqValueToken)
} else {
s = tt.GetPrevOrEqual(ineqValueToken)
}
out := make([]string, 0, 10)
for s != "" {
out = append(out, s)
if geq {
s = tt.GetNext(s)
} else {
s = tt.GetPrev(s)
}
}
return out, nil
}