simplify order.Which so type is always seralized as string

compiler/optimizer/optimizer.go

@@ -816,7 +816,7 @@ func replaceSortAndHeadOrTailWithTop(seq dag.Seq) dag.Seq {
 			case *dag.TailOp:
 				limit = op.Count
 				for i, e := range exprs {
-					exprs[i].Order = !e.Order
+					exprs[i].Order = e.Order.Reverse()
 				}
 				reverse = !reverse
 			default:

compiler/semantic/op.go

@@ -436,7 +436,7 @@ func (t *translator) sortExpr(sch relScope, s ast.SortExpr, reverse bool, inType
 		}
 	}
 	if reverse {
-		o = !o
+		o = o.Reverse()
 	}
 	n := order.NullsLast
 	if s.Nulls != nil {

order/direction.go

@@ -30,6 +30,13 @@ func ParseDirection(s string) (Direction, error) {
 	}
 }
 
+func (d Direction) Which() Which {
+	if d == Down {
+		return Desc
+	}
+	return Asc
+}
+
 func (d Direction) HasOrder(which Which) bool {
 	switch d {
 	case Up:

order/which.go

@@ -1,37 +1,19 @@
 package order
 
 import (
-	"encoding/json"
 	"fmt"
 	"strings"
-
-	"github.com/brimdata/super"
-	"github.com/brimdata/super/sup"
 )
 
-type Which bool
+type Which string
 
 const (
-	Asc  Which = false
-	Desc Which = true
+	Asc  Which = "asc"
+	Desc Which = "desc"
 )
 
-func Parse(s string) (Which, error) {
-	switch strings.ToLower(s) {
-	case "asc":
-		return Asc, nil
-	case "desc":
-		return Desc, nil
-	default:
-		return false, fmt.Errorf("unknown order: %s", s)
-	}
-}
-
 func (w Which) String() string {
-	if w == Desc {
-		return "desc"
-	}
-	return "asc"
+	return string(w)
 }
 
 func (w Which) Direction() Direction {
@@ -41,43 +23,28 @@ func (w Which) Direction() Direction {
 	return Up
 }
 
-// NullsMax returns the Nulls value corresponding to w and nullsMax.
-func (w Which) NullsMax(nullsMax bool) Nulls {
-	if w == Asc && nullsMax || w == Desc && !nullsMax {
-		return NullsLast
-	}
-	return NullsFirst
-}
-
-func (w Which) MarshalJSON() ([]byte, error) {
-	return json.Marshal(w.String())
-}
-
-func (w *Which) UnmarshalJSON(b []byte) error {
-	var s string
-	if err := json.Unmarshal(b, &s); err != nil {
-		return err
-	}
-	switch s {
+func Parse(s string) (Which, error) {
+	switch strings.ToLower(s) {
 	case "asc":
-		*w = Asc
+		return Asc, nil
 	case "desc":
-		*w = Desc
+		return Desc, nil
 	default:
-		return fmt.Errorf("unknown order: %s", s)
+		return "", fmt.Errorf("unknown order: %s", s)
 	}
-	return nil
 }
 
-func (w Which) MarshalBSUP(m *sup.MarshalBSUPContext) (super.Type, error) {
-	return m.MarshalValue(w.String())
+func (w Which) Reverse() Which {
+	if w == Asc {
+		return Desc
+	}
+	return Asc
 }
 
-func (w *Which) UnmarshalBSUP(u *sup.UnmarshalBSUPContext, val super.Value) error {
-	which, err := Parse(string(val.Bytes()))
-	if err != nil {
-		return err
+// NullsMax returns the Nulls value corresponding to w and nullsMax.
+func (w Which) NullsMax(nullsMax bool) Nulls {
+	if w == Asc && nullsMax || w == Desc && !nullsMax {
+		return NullsLast
 	}
-	*w = which
-	return nil
+	return NullsFirst
 }

runtime/sam/op/aggregate/aggregate.go

@@ -77,7 +77,7 @@ func NewAggregator(ctx context.Context, sctx *super.Context, keyRefs, keyExprs,
 	}
 	var keyCompare, valueCompare expr.CompareFn
 	nkeys := len(keyExprs)
-	o := order.Which(inputDir < 0)
+	o := inputDir.Which()
 	if nkeys > 0 && inputDir != 0 {
 		keySortExpr := expr.NewSortExpr(keyRefs[0], o, o.NullsMax(true))
 		keyCompare = expr.NewComparator(keySortExpr).WithMissingAsNull().Compare