memory/provider.go doesn't use a pointer receiver causing the struct to be copied

[tw1nk]

go-mysql-server/memory/provider.go

Line 33 in 057afd4

func (d memoryDBProvider) Database(name string) (sql.Database, error) {

go-mysql-server/memory/provider.go

Line 52 in 057afd4

func (d memoryDBProvider) HasDatabase(name string) bool {

go-mysql-server/memory/provider.go

Line 61 in 057afd4

func (d memoryDBProvider) AllDatabases() []sql.Database {

go-mysql-server/memory/provider.go

Line 78 in 057afd4

func (d memoryDBProvider) CreateDatabase(ctx *sql.Context, name string) (err error) {

go-mysql-server/memory/provider.go

Line 88 in 057afd4

func (d memoryDBProvider) DropDatabase(ctx *sql.Context, name string) (err error) {

[tw1nk]

func TestProviderHasPointerReceiver(t *testing.T) {
	provider := &memoryDBProvider{}
	ref := reflect.ValueOf(provider).Elem().Type()

	for i := 0; i < ref.NumMethod(); i++ {
		method := ref.Method(i)
		if method.IsExported() {
			function := method.Func
			if function.Type().NumIn() > 0 {
				firstArg := function.Type().In(0)
				if firstArg.Kind() != reflect.Ptr {
					t.Errorf("method: memoryDBProvider.%s doesn't have a pointer receiver", method.Name)
				}
			}
		}
	}
}

[zachmu]

This is intentional. The fields in memoryDbProvider are all pointer or map types themselves, so copying the struct is safe.

From a performance perspective, it's not straightforward when a pointer type outperforms a struct as a receiver. You have to benchmark the specific use case to be sure. But you're trading the higher cost of copying a struct v. a pointer with creating memory pressure via pointers. It probably doesn't matter much one way or the other here.