Avoid sorting fields for each written object.

internal/collection/collection.go

@@ -2,6 +2,7 @@ package collection
 
 import (
 	"runtime"
+	"sort"
 
 	"github.com/tidwall/btree"
 	"github.com/tidwall/geoindex"
@@ -319,6 +320,7 @@ func (c *Collection) FieldArr() []string {
 	for field, i := range c.fieldMap {
 		arr[i] = field
 	}
+	sort.Strings(arr)
 	return arr
 }
 

internal/server/crud.go

@@ -2,7 +2,6 @@ package server
 
 import (
 	"bytes"
-	"sort"
 	"strconv"
 	"strings"
 	"time"
@@ -23,22 +22,12 @@ type fvt struct {
 	value float64
 }
 
-type byField []fvt
+func orderFields(fmap map[string]int, farr []string, fields []float64) []fvt {
-
-func (a byField) Len() int {
-	return len(a)
-}
-func (a byField) Less(i, j int) bool {
-	return a[i].field < a[j].field
-}
-func (a byField) Swap(i, j int) {
-	a[i], a[j] = a[j], a[i]
-}
-
-func orderFields(fmap map[string]int, fields []float64) []fvt {
 	var fv fvt
+	var idx int
 	fvs := make([]fvt, 0, len(fmap))
-	for field, idx := range fmap {
+	for _, field := range farr {
+		idx = fmap[field]
 		if idx < len(fields) {
 			fv.field = field
 			fv.value = fields[idx]
@@ -47,7 +36,6 @@ func orderFields(fmap map[string]int, fields []float64) []fvt {
 			}
 		}
 	}
-	sort.Sort(byField(fvs))
 	return fvs
 }
 func (server *Server) cmdBounds(msg *Message) (resp.Value, error) {
@@ -255,7 +243,7 @@ func (server *Server) cmdGet(msg *Message) (resp.Value, error) {
 		return NOMessage, errInvalidNumberOfArguments
 	}
 	if withfields {
-		fvs := orderFields(col.FieldMap(), fields)
+		fvs := orderFields(col.FieldMap(), col.FieldArr(), fields)
 		if len(fvs) > 0 {
 			fvals := make([]resp.Value, 0, len(fvs)*2)
 			if msg.OutputType == JSON {

internal/server/scanner.go

@@ -485,7 +485,7 @@ func (sw *scanWriter) writeObject(opts ScanWriterParams) bool {
 			}
 
 			if sw.hasFieldsOutput() {
-				fvs := orderFields(sw.fmap, opts.fields)
+				fvs := orderFields(sw.fmap, sw.farr, opts.fields)
 				if len(fvs) > 0 {
 					fvals := make([]resp.Value, 0, len(fvs)*2)
 					for i, fv := range fvs {