增加了连接缓存，参考beego orm

pool.go

@@ -0,0 +1,286 @@
+package gorm
+
+import (
+"fmt"
+"time"
+"sync"
+
+)
+
+
+// database driver constant int.
+type DriverType int
+
+const (
+_           DriverType = iota // int enum type
+DR_MySQL                      // mysql
+DR_Sqlite                     // sqlite
+DR_Oracle                     // oracle
+DR_Postgres                   // pgsql
+)
+
+// database driver string.
+type driverDB string
+
+// get type constant int of current driver..
+func (d driverDB) Type() DriverType {
+a, _ := dataBaseCache.get(string(d))
+return a.Driver
+}
+
+// get name of current driver
+func (d driverDB) Name() string {
+return string(d)
+}
+
+
+
+var (
+dataBaseCache = &_dbCache{cache: make(map[string]*alias)}
+drivers = map[string]DriverType{
+"mysql":    DR_MySQL,
+"postgres": DR_Postgres,
+"sqlite3":  DR_Sqlite,
+}
+
+)
+
+// database alias cacher.
+type _dbCache struct {
+mux   sync.RWMutex
+cache map[string]*alias
+}
+
+// add database alias with original name.
+func (ac *_dbCache) add(name string, al *alias) (added bool) {
+ac.mux.Lock()
+defer ac.mux.Unlock()
+if _, ok := ac.cache[name]; ok == false {
+ac.cache[name] = al
+added = true
+}
+return
+}
+
+// get database alias if cached.
+func (ac *_dbCache) get(name string) (al *alias, ok bool) {
+ac.mux.RLock()
+defer ac.mux.RUnlock()
+al, ok = ac.cache[name]
+return
+}
+
+// get default alias.
+func (ac *_dbCache) getDefault() (al *alias) {
+al, _ = ac.get("default")
+return
+}
+
+type alias struct {
+Name         string
+Driver       DriverType
+DriverName   string
+DataSource   string
+MaxIdleConns int
+MaxOpenConns int
+DB           *DB
+TZ           *time.Location
+Engine       string
+}
+
+
+func addAliasWthDB(aliasName, driverName string, db *DB) (*alias, error) {
+al := new(alias)
+al.Name = aliasName
+al.DriverName = driverName
+al.DB = db
+
+if dr, ok := drivers[driverName]; ok {
+al.Driver = dr
+} else {
+return nil, fmt.Errorf("driver name `%s` have not registered", driverName)
+}
+
+
+if dataBaseCache.add(aliasName, al) == false {
+return nil, fmt.Errorf("DataBase alias name `%s` already registered, cannot reuse", aliasName)
+}
+
+return al, nil
+}
+
+func AddAliasWthDB(aliasName, driverName string, db *DB) error {
+_, err := addAliasWthDB(aliasName, driverName, db)
+return err
+}
+
+// Setting the database connect params. Use the database driver self dataSource args.
+func RegisterDataBase(aliasName, driverName, dataSource string, params ...int) error {
+var (
+db *DB
+al  *alias
+)
+
+//	db, err = sql.Open(driverName, dataSource)
+_db, err := Open(driverName, dataSource)
+db=&_db
+
+
+if err != nil {
+err = fmt.Errorf("register db `%s`, %s", aliasName, err.Error())
+goto end
+}
+
+al, err = addAliasWthDB(aliasName, driverName, db)
+if err != nil {
+goto end
+}
+
+al.DataSource = dataSource
+
+
+for i, v := range params {
+switch i {
+case 0:
+SetMaxIdleConns(al.Name, v)
+case 1:
+SetMaxOpenConns(al.Name, v)
+}
+}
+
+end:
+if err != nil {
+if db != nil {
+db.Close()
+}
+}
+
+return err
+}
+
+
+
+// Register a database driver use specify driver name, this can be definition the driver is which database type.
+func RegisterDriver(driverName string, typ DriverType) error {
+if t, ok := drivers[driverName]; ok == false {
+drivers[driverName] = typ
+} else {
+if t != typ {
+return fmt.Errorf("driverName `%s` db driver already registered and is other type\n", driverName)
+}
+}
+return nil
+}
+
+
+// Change the database default used timezone
+func SetDataBaseTZ(aliasName string, tz *time.Location) error {
+if al, ok := dataBaseCache.get(aliasName); ok {
+al.TZ = tz
+} else {
+return fmt.Errorf("DataBase alias name `%s` not registered\n", aliasName)
+}
+return nil
+}
+func detectTZ(al *alias) {
+// orm timezone system match database
+// default use Local
+al.TZ = time.Local
+
+if al.DriverName == "sphinx" {
+return
+}
+
+switch al.Driver {
+case DR_MySQL:
+row := al.DB.Raw("SELECT TIMEDIFF(NOW(), UTC_TIMESTAMP)")
+var tz string
+row.Scan(&tz)
+if len(tz) >= 8 {
+if tz[0] != '-' {
+tz = "+" + tz
+}
+t, err := time.Parse("-07:00:00", tz)
+if err == nil {
+al.TZ = t.Location()
+} else {
+fmt.Printf("Detect DB timezone: %s %s\n", tz, err.Error())
+}
+}
+
+// get default engine from current database
+row = al.DB.Raw("SELECT ENGINE, TRANSACTIONS FROM information_schema.engines WHERE SUPPORT = 'DEFAULT'")
+
+type Egtx struct {
+engine string
+tx bool
+}
+var eg Egtx
+row.Scan(&eg)
+
+if eg.engine != "" {
+al.Engine = eg.engine
+} else {
+al.Engine = "INNODB"
+}
+
+case DR_Sqlite:
+al.TZ = time.UTC
+
+case DR_Postgres:
+row := al.DB.Raw("SELECT current_setting('TIMEZONE')")
+var tz string
+row.Scan(&tz)
+loc, err := time.LoadLocation(tz)
+if err == nil {
+al.TZ = loc
+} else {
+fmt.Printf("Detect DB timezone: %s %s\n", tz, err.Error())
+}
+}
+}
+
+
+// get table alias.
+func getDbAlias(name string) *alias {
+if al, ok := dataBaseCache.get(name); ok {
+return al
+} else {
+panic(fmt.Errorf("unknown DataBase alias name %s", name))
+}
+}
+
+// Change the max idle conns for *sql.DB, use specify database alias name
+func SetMaxIdleConns(aliasName string, maxIdleConns int) {
+al := getDbAlias(aliasName)
+al.MaxIdleConns = maxIdleConns
+al.DB.DB().SetMaxIdleConns(maxIdleConns)
+}
+
+// Change the max open conns for *sql.DB, use specify database alias name
+func SetMaxOpenConns(aliasName string, maxOpenConns int) {
+al := getDbAlias(aliasName)
+al.MaxOpenConns = maxOpenConns
+al.DB.DB().SetMaxOpenConns(maxOpenConns)
+
+}
+
+// Get *sql.DB from registered database by db alias name.
+// Use "default" as alias name if you not set.
+func GetDB(aliasNames ...string) (*DB, error) {
+var name string
+if len(aliasNames) > 0 {
+name = aliasNames[0]
+} else {
+name = "default"
+}
+if al, ok := dataBaseCache.get(name); ok {
+return al.DB, nil
+} else {
+return nil, fmt.Errorf("DataBase of alias name `%s` not found\n", name)
+}
+}
+
+
+
+