code: func (d SelectAllBtnDef) getQuery() *search.SearchQuery {
  	predicate := d.Props().callbacks.GetQuery()
  	if !strings.HasPrefix(predicate, "ref:") {
  		return &search.SearchQuery{
  			Limit:      -1,
  			Expression: predicate,
  		}
  	}
  
  	// If we've got a ref: predicate, assume the given blobRef is a container, and
  	// find its children.
  	blobRef := strings.TrimPrefix(predicate, "ref:")
  	br, ok := blob.Parse(blobRef)
  	if !ok {
  		println(`Invalid blobRef in "ref:" predicate: ` + blobRef)
  		return nil
  	}
  	return &search.SearchQuery{
  		Limit: -1,
  		Constraint: &search.Constraint{Permanode: &search.PermanodeConstraint{
  			Relation: &search.RelationConstraint{
  				Relation: "parent",
  				Any: &search.Constraint{
  					BlobRefPrefix: br.String(),
  				},
  			},
  		}},
  	}
  }
docs: // getQuery returns the query corresponding to the current search in the web UI.