provide common method QueryOne for single row queries

storage/tracking/tracking.go

@@ -99,7 +99,9 @@ func (cont *Container) setupQuerySpec(spec *querySpec) *querySpec {
 	} else {
 		spec.Table = fmt.Sprintf("%s.%s", cont.Storage.Schema, cont.TableName)
 	}
+	if spec.Scols == nil {
 		spec.Scols = append(cont.HeadFields, "timestamp", "data", "trackid")
+	}
 	for i, v := range spec.Headvals {
 		if v != "" {
 			spec.Qucols = append(spec.Qucols, cont.HeadFields[i])
@@ -124,36 +126,31 @@ type querySpec struct {
 }
 
 func (cont *Container) Get(id lib.Ident) *Track {
-	db := cont.Storage
-	var tr *Track
-	proc := func(r *sql.Rows) error {
-		tr = cont.ItemFactory(cont)
-		return tr.ScanP(r)
-	}
 	quSpec := &querySpec{
 		Qucols: lib.StrSlice{"trackid"},
 		Quvals: []any{id},
 	}
-	cont.setupQuerySpec(quSpec)
+	return cont.QueryOne(quSpec)
-	sql := storage.BuildSql(SqlSelect, quSpec)
-	db.Query(proc, sql, id)
-	return tr
 }
 
 func (cont *Container) QueryLast(hv ...string) *Track {
+	quSpec := &querySpec{
+		Headvals: hv,
+		Ordcols:  lib.StrSlice{"timestamp"},
+		Limit:    1,
+	}
+	return cont.QueryOne(quSpec)
+}
+
+func (cont *Container) QueryOne(quSpec *querySpec) *Track {
 	db := cont.Storage
 	var tr *Track
 	proc := func(r *sql.Rows) error {
 		tr = cont.ItemFactory(cont)
 		return tr.ScanP(r)
 	}
-	quSpec := &querySpec{
-		Headvals: hv,
-		Ordcols:  lib.StrSlice{"timestamp"},
-	}
 	cont.setupQuerySpec(quSpec)
 	sql := storage.BuildSql(SqlSelect, quSpec)
-	println(sql)
 	db.Query(proc, sql, quSpec.Quvals...)
 	return tr
 }