sort: Allow ordering on a per key basis

Change the sort operator so that different ordering can be applied to
each key in the sort.

Closes #4945

api/api.go

@@ -36,10 +36,10 @@ type VersionResponse struct {
 }
 
 type PoolPostRequest struct {
-	Name       string        `json:"name"`
-	SortKey    order.SortKey `json:"layout"`
-	SeekStride int           `json:"seek_stride"`
-	Thresh     int64         `json:"thresh"`
+	Name       string         `json:"name"`
+	SortKeys   order.SortKeys `json:"layout"`
+	SeekStride int            `json:"seek_stride"`
+	Thresh     int64          `json:"thresh"`
 }
 
 type PoolPutRequest struct {

cmd/zed/create/command.go

@@ -70,7 +70,7 @@ func (c *Command) Run(args []string) error {
 	if err != nil {
 		return err
 	}
-	sortKey, err := order.ParseSortKey(c.sortKey)
+	sortKey, err := order.ParseSortKeys(c.sortKey)
 	if err != nil {
 		return err
 	}

compiler/ast/ast.go

@@ -4,7 +4,6 @@ package ast
 
 import (
 	astzed "github.com/brimdata/zed/compiler/ast/zed"
-	"github.com/brimdata/zed/order"
 	"github.com/brimdata/zed/pkg/field"
 )
 
@@ -466,11 +465,11 @@ type (
 		Rparen     int    `json:"rparen"`
 	}
 	Sort struct {
-		Kind       string      `json:"kind" unpack:""`
-		KeywordPos int         `json:"keyword_pos"`
-		Args       []Expr      `json:"args"`
-		Order      order.Which `json:"order"`
-		NullsFirst bool        `json:"nullsfirst"`
+		Kind       string     `json:"kind" unpack:""`
+		KeywordPos int        `json:"keyword_pos"`
+		Reverse    bool       `json:"reverse"`
+		NullsFirst bool       `json:"nullsfirst"`
+		Args       []SortExpr `json:"args"`
 	}
 	Cut struct {
 		Kind       string      `json:"kind" unpack:""`
@@ -638,19 +637,19 @@ type (
 
 type (
 	File struct {
-		Kind       string   `json:"kind" unpack:""`
-		KeywordPos int      `json:"keyword_pos"`
-		Path       Pattern  `json:"path"`
-		Format     string   `json:"format"`
-		SortKey    *SortKey `json:"sort_key"`
-		EndPos     int      `json:"end_pos"`
+		Kind       string     `json:"kind" unpack:""`
+		KeywordPos int        `json:"keyword_pos"`
+		Path       Pattern    `json:"path"`
+		Format     string     `json:"format"`
+		SortKeys   []SortExpr `json:"sort_keys"`
+		EndPos     int        `json:"end_pos"`
 	}
 	HTTP struct {
 		Kind       string      `json:"kind" unpack:""`
 		KeywordPos int         `json:"keyword_pos"`
 		URL        Pattern     `json:"url"`
 		Format     string      `json:"format"`
-		SortKey    *SortKey    `json:"sort_key"`
+		SortKeys   []SortExpr  `json:"sort_keys"`
 		Method     string      `json:"method"`
 		Headers    *RecordExpr `json:"headers"`
 		Body       string      `json:"body"`
@@ -690,10 +689,18 @@ func (x *Pool) End() int { return x.EndPos }
 func (x *File) End() int { return x.EndPos }
 func (x *HTTP) End() int { return x.EndPos }
 
-type SortKey struct {
+type SortExpr struct {
 	Kind  string `json:"kind" unpack:""`
-	Keys  []Expr `json:"keys"`
-	Order string `json:"order"`
+	Expr  Expr   `json:"expr"`
+	Order *ID    `json:"order"`
+}
+
+func (s SortExpr) Pos() int { return s.Expr.Pos() }
+func (s SortExpr) End() int {
+	if s.Order != nil {
+		s.Order.End()
+	}
+	return s.Expr.End()
 }
 
 type Trunk struct {

compiler/ast/dag/expr.go

@@ -1,5 +1,7 @@
 package dag
 
+import "github.com/brimdata/zed/order"
+
 type (
 	Expr interface {
 		ExprDAG()
@@ -117,6 +119,10 @@ type (
 		From Expr   `json:"from"`
 		To   Expr   `json:"to"`
 	}
+	SortExpr struct {
+		Key   Expr        `json:"key"`
+		Order order.Which `json:"order"`
+	}
 	This struct {
 		Kind string   `json:"kind" unpack:""`
 		Path []string `json:"path"`

compiler/ast/dag/op.go

@@ -127,10 +127,10 @@ type (
 		Kind string `json:"kind" unpack:""`
 	}
 	Sort struct {
-		Kind       string      `json:"kind" unpack:""`
-		Args       []Expr      `json:"args"`
-		Order      order.Which `json:"order"`
-		NullsFirst bool        `json:"nullsfirst"`
+		Kind       string     `json:"kind" unpack:""`
+		Args       []SortExpr `json:"args"`
+		NullsFirst bool       `json:"nullsfirst"`
+		Reverse    bool       `json:"reverse"`
 	}
 	Summarize struct {
 		Kind         string       `json:"kind" unpack:""`
@@ -202,25 +202,25 @@ type (
 
 	// DefaultScan scans an input stream provided by the runtime.
 	DefaultScan struct {
-		Kind    string        `json:"kind" unpack:""`
-		Filter  Expr          `json:"filter"`
-		SortKey order.SortKey `json:"sort_key"`
+		Kind     string         `json:"kind" unpack:""`
+		Filter   Expr           `json:"filter"`
+		SortKeys order.SortKeys `json:"sort_keys"`
 	}
 	FileScan struct {
-		Kind    string        `json:"kind" unpack:""`
-		Path    string        `json:"path"`
-		Format  string        `json:"format"`
-		SortKey order.SortKey `json:"sort_key"`
-		Filter  Expr          `json:"filter"`
+		Kind     string         `json:"kind" unpack:""`
+		Path     string         `json:"path"`
+		Format   string         `json:"format"`
+		SortKeys order.SortKeys `json:"sort_keys"`
+		Filter   Expr           `json:"filter"`
 	}
 	HTTPScan struct {
-		Kind    string              `json:"kind" unpack:""`
-		URL     string              `json:"url"`
-		Format  string              `json:"format"`
-		SortKey order.SortKey       `json:"sort_key"`
-		Method  string              `json:"method"`
-		Headers map[string][]string `json:"headers"`
-		Body    string              `json:"body"`
+		Kind     string              `json:"kind" unpack:""`
+		URL      string              `json:"url"`
+		Format   string              `json:"format"`
+		SortKeys order.SortKeys      `json:"sort_keys"`
+		Method   string              `json:"method"`
+		Headers  map[string][]string `json:"headers"`
+		Body     string              `json:"body"`
 	}
 	PoolScan struct {
 		Kind   string      `json:"kind" unpack:""`

compiler/data/source.go

@@ -54,11 +54,11 @@ func (s *Source) CommitObject(ctx context.Context, id ksuid.KSUID, name string)
 	return ksuid.Nil, nil
 }
 
-func (s *Source) SortKey(ctx context.Context, src dag.Op) order.SortKey {
+func (s *Source) SortKeys(ctx context.Context, src dag.Op) order.SortKeys {
 	if s.lake != nil {
-		return s.lake.SortKey(ctx, src)
+		return s.lake.SortKeys(ctx, src)
 	}
-	return order.Nil
+	return nil
 }
 
 func (s *Source) Open(ctx context.Context, zctx *zed.Context, path, format string, pushdown zbuf.Filter, demandOut demand.Demand) (zbuf.Puller, error) {

compiler/describe/analyze.go

@@ -50,7 +50,7 @@ func (*Path) Source()     {}
 type Channel struct {
 	Name            string         `json:"name"`
 	AggregationKeys field.List     `json:"aggregation_keys"`
-	Sort            *order.SortKey `json:"sort"`
+	Sort            order.SortKeys `json:"sort"`
 }
 
 func Analyze(ctx context.Context, query string, src *data.Source, head *lakeparse.Commitish) (*Info, error) {
@@ -85,13 +85,7 @@ func AnalyzeDAG(ctx context.Context, entry dag.Seq, src *data.Source, head *lake
 	aggKeys := describeAggs(entry, []field.List{nil})
 	outputs := collectOutputs(entry)
 	m := make(map[string]int)
-	for i := range sortKeys {
-		// Convert SortKey to a pointer so a nil sort is encoded as null for
-		// JSON/ZSON.
-		var s *order.SortKey
-		if !sortKeys[i].IsNil() {
-			s = &sortKeys[i]
-		}
+	for i, s := range sortKeys {
 		name := outputs[i].Name
 		if k, ok := m[name]; ok {
 			// If output already exists, this means the outputs will be

compiler/kernel/op.go

@@ -15,7 +15,6 @@ import (
 	"github.com/brimdata/zed/compiler/optimizer"
 	"github.com/brimdata/zed/compiler/optimizer/demand"
 	"github.com/brimdata/zed/lake"
-	"github.com/brimdata/zed/order"
 	"github.com/brimdata/zed/pkg/field"
 	"github.com/brimdata/zed/runtime"
 	"github.com/brimdata/zed/runtime/sam/expr"
@@ -187,11 +186,15 @@ func (b *Builder) compileLeaf(o dag.Op, parent zbuf.Puller) (zbuf.Puller, error)
 		return op.NewApplier(b.rctx, parent, dropper, expr.Resetters{}), nil
 	case *dag.Sort:
 		b.resetResetters()
-		fields, err := b.compileExprs(v.Args)
-		if err != nil {
-			return nil, err
+		var sortExprs []expr.SortEvaluator
+		for _, s := range v.Args {
+			k, err := b.compileExpr(s.Key)
+			if err != nil {
+				return nil, err
+			}
+			sortExprs = append(sortExprs, expr.NewSortEvaluator(k, s.Order))
 		}
-		sort, err := sort.New(b.rctx, parent, fields, v.Order, v.NullsFirst, b.resetters)
+		sort, err := sort.New(b.rctx, parent, sortExprs, v.NullsFirst, v.Reverse, b.resetters)
 		if err != nil {
 			return nil, fmt.Errorf("compiling sort: %w", err)
 		}
@@ -672,7 +675,7 @@ func (b *Builder) compile(o dag.Op, parents []zbuf.Puller) ([]zbuf.Puller, error
 		if err != nil {
 			return nil, err
 		}
-		cmp := expr.NewComparator(true, o.Order == order.Desc, e).WithMissingAsNull()
+		cmp := expr.NewComparator(true, expr.NewSortEvaluator(e, o.Order)).WithMissingAsNull()
 		return []zbuf.Puller{merge.New(b.rctx, parents, cmp.Compare, b.resetters)}, nil
 	case *dag.Combine:
 		return []zbuf.Puller{combine.New(b.rctx, parents)}, nil