We will discuss most popular ORM libraries and will perform a brief comparison of them. Also we will see some GORM-specific implementation of query result caching.

1. ORM in Go
Internals, tips & tricks
Dmytro Istratkin
Senior Software Engineer
SoftServe

2. Object-Relational Mapping frameworks history

3. ORM approaches
• Object to schema (code first)
• Schema to object (database first)
• Meet in the middle

4. ORM in Go
Name Stars ⭐️ DBMS support Approach Notes
gorm 15153
MySQL, PostgreSQL, Sqlite3,
MS SQL Server
Code first
xorm 5356
MySQL, PostgreSQL, Sqlite3,
MS SQL Server, Oracle, …
Code first, DB first Codegen, sync
go-pg 3106 PostgreSQL only Code first, DB first
gorp 3099
MySQL, PostgreSQL, Sqlite3,
MS SQL Server, Oracle
Code first
SQLBoiler 2336
MySQL, PostgreSQL, Sqlite3,
MS SQL Server, CockroachDB
DB first Full codegen
reform 815
MySQL, PostgreSQL, Sqlite3,
MS SQL Server
Code first Codegen
go-queryset 457
MySQL, PostgreSQL, Sqlite3,
MS SQL Server
Code first Codegen, on top of GORM

5. GORM
• Transactions
• Hooks
• Associations
• Logger
• Actively developed

6. GORP
• Transactions
• Hooks
• ORM-ish
• Logger
• Discontinued

7. Tips & tricks

8. Query result caching
• About GCache: LRU, LFU, ARC support
• Why GCache is used in current project

9. Caching in GORM: after query
db.Callback().Query().After("gorm:query").Register(”mykey:after_query", func(scope *gorm.Scope) {
key := fmt.Sprintf(“%s”, scope.DB().QueryExpr())
if gch.Has(key) {…}
if value, ok = scope.Get(“cachemarker”); !ok {
value = scope.Value
}
if value == nil {
scope.Log("nothing to cache")
}
if err := gch.SetWithExpire(key, value, 30 * time.Minute); err != nil {…}
})

10. Caching in GORM: before query
db.Callback().Query().Before("gorm:query").Register("my:before_query", func(scope *gorm.Scope) {
key := fmt.Sprintf(“%s”, scope.DB().QueryExpr())
value, err := gch.GetIFPresent(key)
if err == gcache.KeyNotFoundError {…}
dst, ok := scope.Get(“cachemarker”)
if !ok {…}
srcValue, dstValue := indirect(reflect.ValueOf(value)), indirect(reflect.ValueOf(dst))
if !dstValue.CanSet() {…}
dstValue.Set(srcValue)
scope.InstanceSet("gorm:skip_query_callback", nil)
})

11. Caching in GORM: caching marker
var target []struct {
FileName string `gorm:"column:file_name"`
}
db := c.DB().Table("files").
Where("file_id = ?", fileID).
Select("file_name").
Set(“cachemarker”, &target).
Scan(&target)

12. GORM: Explain query
func explainAnalyzeCallback(scope *gorm.Scope) {
vars := strings.TrimPrefix(fmt.Sprintf("%#v", scope.SQLVars), "[]interface {}")
result := []string{fmt.Sprintf("nn%s %sn", scope.SQL, vars)}
query := fmt.Sprintf("EXPLAIN (ANALYZE, COSTS, VERBOSE, BUFFERS) %s", scope.SQL)
rows, err := scope.SQLDB().Query(query, scope.SQLVars...)
if err != nil {…}
defer func() { _ = rows.Close() }()
… // concatenate result
scope.Log(strings.Join(result, "n"))
}

13. GORP: Explain query
func (m GorpExplainLogger) Printf(format string, v ...interface{}) {
query := strings.TrimLeftFunc(v[1].(string), unicode.IsSpace)
ok, values := parseArgs(v[2].(string))
if !ok {...}
var result []string
if _, err := m.executor.Select(&result, "EXPLAIN (ANALYZE, COSTS, VERBOSE, BUFFERS) ”
+ query, values...); err != nil {…}
for _, s := range result {
m.logger.Printf("%s", s)
}
}

14. ORM: Pros
• Only one place for model
• Use your favorite programming language
• SQL is hidden
• DB abstraction

15. ORM: Cons
• ORM has it’s own language
• Configuration
• Poor optimization capabilities
• DB abstraction

16. Links
Repositories:
• GORM: https://github.com/jinzhu/gorm
• XORM: https://github.com/go-xorm/xorm
• GCache: https://github.com/bluele/gcache
Media:
• https://github.com/MariaLetta/free-gophers-pack
• https://ih1.redbubble.net/image.581976886.8080/poster,840x830,f8
f8f8-pad,750x1000,f8f8f8.u2.jpg

17. Questions?