Merge pull request #2744 from gnanakeethan/feature/database-migration

[Proposal] Database Migrations;

migration/doc.go

+/* Package migration enables you to generate migrations back and forth. It generates both migrations.
+
+
+//Creates a table
+m.CreateTable("tablename","InnoDB","utf8");
+
+
+
+//Alter a table
+m.AlterTable("tablename")
+
+
+
+//Standard Column Methods
+* SetDataType
+* SetNullable
+* SetDefault
+* SetUnsigned (use only on integer types unless produces error)
+
+
+//Sets a primary column, multiple calls allowed, standard column methods available
+m.PriCol("id").SetAuto(true).SetNullable(false).SetDataType("INT(10)").SetUnsigned(true)
+
+//UniCol Can be used multiple times, allows standard Column methods. Use same "index" string to add to same index
+m.UniCol("index","column")
+
+//Standard Column Initialisation, can call .Remove() after NewCol("") on alter to remove
+m.NewCol("name").SetDataType("VARCHAR(255) COLLATE utf8_unicode_ci").SetNullable(false)
+m.NewCol("value").SetDataType("DOUBLE(8,2)").SetNullable(false)
+
+//Rename Columns , only use with Alter table, doesn't works with Create, prefix standard column methods with "Old" to
+//create a true reversible migration eg: SetOldDataType("DOUBLE(12,3)")
+m.RenameColumn("from","to")...
+
+
+//Foreign Columns, single columns are only supported, SetOnDelete & SetOnUpdate are available, call appropriately.
+//Supports standard column methods, automatic reverse.
+m.ForeignCol("local_col","foreign_col","foreign_table")
+
+*/
+package migration

migration/migration.go

@@ -52,6 +52,26 @@ type Migrationer interface {
 	GetCreated() int64
 }
 
+//Migration defines the migrations by either SQL or DDL
+type Migration struct {
+	sqls           []string
+	Created        string
+	TableName      string
+	Engine         string
+	Charset        string
+	ModifyType     string
+	Columns        []*Column
+	Indexes        []*Index
+	Primary        []*Column
+	Uniques        []*Unique
+	Foreigns       []*Foreign
+	Renames        []*RenameColumn
+	RemoveColumns  []*Column
+	RemoveIndexes  []*Index
+	RemoveUniques  []*Unique
+	RemoveForeigns []*Foreign
+}
+
 var (
 	migrationMap map[string]Migrationer
 )
@@ -60,20 +80,34 @@ func init() {
 	migrationMap = make(map[string]Migrationer)
 }
 
-// Migration the basic type which will implement the basic type
-type Migration struct {
-	sqls    []string
-	Created string
-}
-
 // Up implement in the Inheritance struct for upgrade
 func (m *Migration) Up() {
 
+	switch m.ModifyType {
+	case "reverse":
+		m.ModifyType = "alter"
+	case "delete":
+		m.ModifyType = "create"
+	}
+	m.sqls = append(m.sqls, m.GetSQL())
 }
 
 // Down implement in the Inheritance struct for down
 func (m *Migration) Down() {
 
+	switch m.ModifyType {
+	case "alter":
+		m.ModifyType = "reverse"
+	case "create":
+		m.ModifyType = "delete"
+	}
+	m.sqls = append(m.sqls, m.GetSQL())
+}
+
+//Migrate adds the SQL to the execution list
+func (m *Migration) Migrate(migrationType string) {
+	m.ModifyType = migrationType
+	m.sqls = append(m.sqls, m.GetSQL())
 }
 
 // SQL add sql want to execute