Method helpProcessTask

worker/task.go:1073–1203

(ctx context.Context, q *pb.Query, gid uint32)

}

func (qs *queryState) helpProcessTask(ctx context.Context, q *pb.Query, gid uint32) (
	*pb.Result, error) {

	span := trace.SpanFromContext(ctx)
	out := new(pb.Result)
	attr := q.Attr

	srcFn, err := parseSrcFn(ctx, q)
	if err != nil {
		return nil, err
	}

	if q.Reverse && !schema.State().IsReversed(ctx, attr) {
		return nil, errors.Errorf("Predicate %s doesn't have reverse edge", x.ParseAttr(attr))
	}

	if needsIndex(srcFn.fnType, q.UidList) && !schema.State().IsIndexed(ctx, q.Attr) {
		return nil, errors.Errorf("Predicate %s is not indexed", x.ParseAttr(q.Attr))
	}

	if len(q.Langs) > 0 && !schema.State().HasLang(attr) {
		return nil, errors.Errorf("Language tags can only be used with predicates of string type"+
			" having @lang directive in schema. Got: [%v]", x.ParseAttr(attr))
	}
	if len(q.Langs) == 1 && q.Langs[0] == "*" {
		// Reset the Langs fields. The ExpandAll field is set to true already so there's no
		// more need to store the star value in this field.
		q.Langs = nil
	}

	typ, err := schema.State().TypeOf(attr)
	if err != nil {
		// All schema checks are done before this, this type is only used to
		// convert it to schema type before returning.
		// Schema type won't be present only if there is no data for that predicate
		// or if we load through bulk loader.
		typ = types.DefaultID
	}
	out.List = schema.State().IsList(attr)
	srcFn.atype = typ

	// Reverse attributes might have more than 1 results even if the original attribute
	// is not a list.
	if q.Reverse {
		out.List = true
	}

	opts := posting.ListOptions{
		ReadTs:   q.ReadTs,
		AfterUid: q.AfterUid,
		First:    int(q.First + q.Offset),
	}
	// If we have srcFunc and Uids, it means its a filter. So we intersect.
	if srcFn.fnType != notAFunction && q.UidList != nil && len(q.UidList.Uids) > 0 {
		opts.Intersect = q.UidList
	}

	args := funcArgs{q, gid, srcFn, out}