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myorm.go
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myorm.go
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package myorm
import (
"database/sql"
"fmt"
"github.com/GoodOneGuy/myorm/dialect"
"github.com/GoodOneGuy/myorm/session"
"log"
"strings"
)
type Engine struct {
db *sql.DB
dialect dialect.Dialect
}
func NewEngine(driver, source string) (e *Engine, err error) {
db, err := sql.Open(driver, source)
if err != nil {
log.Println("connect database fail, err=", err)
return
}
if err = db.Ping(); err != nil {
return
}
dial, ok := dialect.GetDialect(driver)
if !ok {
log.Printf("dialect %s Not Found\n", driver)
return
}
e = &Engine{
db: db,
dialect: dial,
}
log.Println("connect database success")
return
}
func (e *Engine) Close() {
err := e.db.Close()
if err != nil {
log.Println("close database fail, err=", err)
return
}
log.Println("close database success")
}
func (e *Engine) NewSession() *session.Session {
return session.New(e.db, e.dialect)
}
type TxFunc func(*session.Session) (interface{}, error)
func (e *Engine) Transaction(fn TxFunc) (result interface{}, err error) {
s := e.NewSession()
if err = s.Begin(); err != nil {
return nil, err
}
defer func() {
if p := recover(); p != nil {
s.Rollback()
} else if err != nil {
s.Rollback()
} else {
s.Commit()
}
}()
return fn(s)
}
// difference returns a - b
func difference(a []string, b []string) (diff []string) {
mapB := make(map[string]bool)
for _, v := range b {
mapB[v] = true
}
for _, v := range a {
if _, ok := mapB[v]; !ok {
diff = append(diff, v)
}
}
return
}
// Migrate table
func (engine *Engine) Migrate(value interface{}) error {
_, err := engine.Transaction(func(s *session.Session) (result interface{}, err error) {
if !s.Model(value).HasTable() {
log.Printf("table %s doesn't exist\n", s.RefTable().Name)
return nil, s.CreateTable()
}
table := s.RefTable()
rows, _ := s.Raw(fmt.Sprintf("SELECT * FROM %s LIMIT 1", table.Name)).QueryRows()
columns, _ := rows.Columns()
addCols := difference(table.FieldNames, columns)
delCols := difference(columns, table.FieldNames)
log.Printf("added cols %v, deleted cols %v\n", addCols, delCols)
for _, col := range addCols {
f := table.GetField(col)
sqlStr := fmt.Sprintf("ALTER TABLE %s ADD COLUMN %s %s;", table.Name, f.Name, f.Type)
if _, err = s.Raw(sqlStr).Exec(); err != nil {
return
}
}
if len(delCols) == 0 {
return
}
tmp := "tmp_" + table.Name
fieldStr := strings.Join(table.FieldNames, ", ")
s.Raw(fmt.Sprintf("CREATE TABLE %s AS SELECT %s from %s;", tmp, fieldStr, table.Name))
s.Raw(fmt.Sprintf("DROP TABLE %s;", table.Name))
s.Raw(fmt.Sprintf("ALTER TABLE %s RENAME TO %s;", tmp, table.Name))
_, err = s.Exec()
return
})
return err
}