added noupdate field tag to exclude column from updates

Author: rck109d

db.go

@@ -245,7 +245,7 @@ func makeUpdatePlan(m *Model) updatePlan {
 
 	var setColumns []string
 	for _, col := range m.mappedColumns {
-		if col.AutoIncr || primaryKey[col.Name] {
+		if col.AutoIncr || primaryKey[col.Name] || m.fields[col.Name].noupdate {
 			continue
 		}
 		setColumns = append(setColumns, col.Name)

db_test.go

@@ -1827,13 +1827,15 @@ const versionedUsersDDL = `
 CREATE TABLE users (
   id   BIGINT UNSIGNED NOT NULL AUTO_INCREMENT PRIMARY KEY,
   name VARCHAR(255) NOT NULL,
-  ver  INT NOT NULL
+  ver  INT NOT NULL,
+  created_at BIGINT NOT NULL
 )`
 
 type VersionedUser struct {
-	ID      uint64 `db:"id"`
-	Name    string `db:"name"`
-	Version int    `db:"ver,optlock"`
+	ID        uint64 `db:"id"`
+	Name      string `db:"name"`
+	Version   int    `db:"ver,optlock"`
+	CreatedAt int64  `db:"created_at,noupdate"`
 }
 
 func TestVersionedUser_base(t *testing.T) {
@@ -1844,16 +1846,19 @@ func TestVersionedUser_base(t *testing.T) {
 	}
 
 	// Insert
+	createdAt := time.Date(2022, time.January, 1, 0, 0, 0, 0, time.UTC)
 	u := &VersionedUser{
-		Name:    "foo",
-		Version: 1,
+		Name:      "foo",
+		Version:   1,
+		CreatedAt: createdAt.UnixMilli(),
 	}
 	if err := db.Insert(u); err != nil {
 		t.Fatal(err)
 	}
 
 	// Update
 	u.Name = "bar"
+	u.CreatedAt = createdAt.Add(time.Hour).UnixMilli()
 	if count, err := db.Update(u); err != nil {
 		t.Fatal(err)
 	} else if count != 1 {
@@ -1874,6 +1879,9 @@ func TestVersionedUser_base(t *testing.T) {
 	if stored.Version != 2 {
 		t.Fatalf("expected stored version %d, was at version %d", 2, stored.Version)
 	}
+	if stored.CreatedAt != createdAt.UnixMilli() {
+		t.Fatalf("expected stored created_at %d, was at created_at %d", createdAt.UnixMilli(), stored.CreatedAt)
+	}
 }
 
 func TestVersionedUser_concurrentModification(t *testing.T) {

reflect.go

@@ -22,14 +22,16 @@ import (
 
 type fieldDesc struct {
 	reflect.StructField
-	optlock bool
+	optlock  bool
+	noupdate bool
 }
 
 type fieldMap map[string]fieldDesc
 
 const (
-	tagName    = "db"
-	tagOptlock = "optlock"
+	tagName        = "db"
+	tagSubOptlock  = "optlock"
+	tagSubNoUpdate = "noupdate"
 )
 
 // getMapping returns a mapping for the type t, using the tagName and
@@ -52,7 +54,7 @@ func getMapping(t reflect.Type, mapFunc func(string) string) fieldMap {
 		for fieldPos := 0; fieldPos < tq.t.NumField(); fieldPos++ {
 			f := tq.t.Field(fieldPos)
 
-			name, optlock := readTag(f.Tag.Get(tagName))
+			name, optlock, noupdate := readTag(f.Tag.Get(tagName))
 
 			// Breadth first search of untagged anonymous embedded structs.
 			if f.Anonymous && f.Type.Kind() == reflect.Struct && name == "" {
@@ -86,18 +88,26 @@ func getMapping(t reflect.Type, mapFunc func(string) string) fieldMap {
 			// Add it to the map at the current position.
 			sf := f
 			sf.Index = appendIndex(tq.p, fieldPos)
-			m[name] = fieldDesc{sf, optlock}
+			m[name] = fieldDesc{sf, optlock, noupdate}
 		}
 	}
 	return m
 }
 
-func readTag(tag string) (string, bool) {
-	if comma := strings.Index(tag, ","); comma != -1 {
-		return tag[0:comma], tag[comma+1:len(tag)] == tagOptlock
-	} else {
-		return tag, false
+func readTag(tag string) (name string, optLock bool, noUpdate bool) {
+	values := strings.Split(tag, ",")
+	name = values[0]
+	if len(values) > 1 {
+		for _, s := range values[1:] {
+			switch s {
+			case tagSubOptlock:
+				optLock = true
+			case tagSubNoUpdate:
+				noUpdate = true
+			}
+		}
 	}
+	return name, optLock, noUpdate
 }
 
 func getDBFields(t reflect.Type) fieldMap {

reflect_test.go

@@ -158,26 +158,32 @@ func TestMapping(t *testing.T) {
 
 func TestReadTag(t *testing.T) {
 	testCases := []struct {
-		tag     string
-		name    string
-		optlock bool
+		tag      string
+		name     string
+		optlock  bool
+		noupdate bool
 	}{
-		{"-", "-", false},
-		{"foo", "foo", false},
-		{"foo,", "foo", false},
-		{"foo,optlock", "foo", true},
-		{",optlock", "", true},
-		{",wrong", "", false},
-		{",", "", false},
+		{"-", "-", false, false},
+		{"foo", "foo", false, false},
+		{"foo,", "foo", false, false},
+		{"foo,optlock", "foo", true, false},
+		{",optlock", "", true, false},
+		{",wrong", "", false, false},
+		{",noupdate", "", false, true},
+		{",optlock,noupdate", "", true, true},
+		{",", "", false, false},
 	}
 	for _, c := range testCases {
-		name, optlock := readTag(c.tag)
+		name, optlock, noupdate := readTag(c.tag)
 		if name != c.name {
 			t.Errorf("%s: expected name '%s', actual '%s'", c.tag, c.name, name)
 		}
 		if optlock != c.optlock {
 			t.Errorf("%s: expected optlock '%t', actual '%t'", c.tag, c.optlock, optlock)
 		}
+		if noupdate != c.noupdate {
+			t.Errorf("%s: expected optlock '%t', actual '%t'", c.tag, c.noupdate, noupdate)
+		}
 	}
 }