fix: improve zero checker for ptr values

internal/dbtest/db_test.go

@@ -223,6 +223,7 @@ func TestDB(t *testing.T) {
 		{testInterfaceAny},
 		{testInterfaceJSON},
 		{testScanBytes},
+		{testPointers},
 	}
 
 	testEachDB(t, func(t *testing.T, dbName string, db *bun.DB) {
@@ -847,3 +848,28 @@ func testScanBytes(t *testing.T, db *bun.DB) {
 
 	require.Equal(t, models, models1)
 }
+
+func testPointers(t *testing.T, db *bun.DB) {
+	type Model struct {
+		ID  *int64 `bun:",allowzero,default:0"`
+		Str *string
+	}
+
+	ctx := context.Background()
+
+	err := db.ResetModel(ctx, (*Model)(nil))
+	require.NoError(t, err)
+
+	id := int64(1)
+	str := "hello"
+	models := []Model{
+		{},
+		{ID: &id, Str: &str},
+	}
+	_, err = db.NewInsert().Model(&models).Exec(ctx)
+	require.NoError(t, err)
+
+	var models2 []Model
+	err = db.NewSelect().Model(&models2).Order("id ASC").Scan(ctx)
+	require.NoError(t, err)
+}

schema/table.go

@@ -193,10 +193,15 @@ func (t *Table) initFields() {
 		}
 	}
 	if len(t.PKs) == 1 {
-		switch t.PKs[0].IndirectType.Kind() {
+		pk := t.PKs[0]
+		if pk.SQLDefault != "" {
+			return
+		}
+
+		switch pk.IndirectType.Kind() {
 		case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64,
 			reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64:
-			t.PKs[0].AutoIncrement = true
+			pk.AutoIncrement = true
 		}
 	}
 }
@@ -359,7 +364,7 @@ func (t *Table) newField(f reflect.StructField, index []int) *Field {
 	field.DiscoveredSQLType = DiscoverSQLType(field.IndirectType)
 	field.Append = t.dialect.FieldAppender(field)
 	field.Scan = FieldScanner(t.dialect, field)
-	field.IsZero = FieldZeroChecker(field)
+	field.IsZero = zeroChecker(field.StructField.Type)
 
 	if v, ok := tag.Options["alt"]; ok {
 		t.FieldMap[v] = field

schema/zerochecker.go

@@ -13,10 +13,6 @@ type isZeroer interface {
 
 type IsZeroerFunc func(reflect.Value) bool
 
-func FieldZeroChecker(field *Field) IsZeroerFunc {
-	return zeroChecker(field.IndirectType)
-}
-
 func zeroChecker(typ reflect.Type) IsZeroerFunc {
 	if typ.Implements(isZeroerType) {
 		return isZeroInterface