[Proposal] Database Migrations;

Summary: The database migrations now can be created using the methods on
the migration struct. it does not break any existing migration features.
it upgrades the migration struct and adds few more struct types so that
the migrations can be efficiently generated for create, alter, reverse,
drop.

Current Features:
* Supports creation of columns
   * `m.NewCol("name").SetDataType("VARCHAR(10)").SetNullable("true")`
   * **NOTE** `SetNullable` & `SetDefault` methods should not be called on
   same column for consistency
* Supports addition of primary keys
   * `m.PriCol("id").SetDataType("INT(10)").SetNullable("true")`
   * **NOTE** `setAuto(true)` can be only called on Primary keys
* Supports addition of unique keys
   * `m.UniCol("unique_index","column_name").SetDataType("VARCHAR(23)").SetNullable("true")`
   * **NOTE** `UniCol` can be called again with the same index name to
   add column to the index
* Supports rename of columns
   * `m.RenameColumn("from_name","to_name")`
   * Allows standard column methods and methods such that, `SetOldDefault` allows
   reversibility of renames

* TODO:
   * ForeignKey

Signed-off-by: Gnanakeethan Balasubramaniam <gnanakeethan@gmail.com>

migration/ddl.go

@@ -12,42 +12,327 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
-package migration
+package m
 
-// Table store the tablename and Column
+import (
-type Table struct {
+	"fmt"
-	TableName string
+
+	"github.com/astaxie/beego"
+)
+
+// Index struct defines the structure of Index Columns
+type Index struct {
+	Name string
+}
+
+// Foreign struct defines a single foreign relationship
+type Foreign struct {
+	Column        *Column
+	ForeignTable  string
+	ForeignColumn string
+}
+
+// Unique struct defines a single unique key combination
+type Unique struct {
+	Definition string
 	Columns    []*Column
 }
 
-// Create return the create sql
+//Column struct defines a single column of a table
-func (t *Table) Create() string {
-	return ""
-}
-
-// Drop return the drop sql
-func (t *Table) Drop() string {
-	return ""
-}
-
-// Column define the columns name type and Default
 type Column struct {
 	Name     string
-	Type    string
+	Inc      string
-	Default interface{}
+	Null     string
+	Default  string
+	Unsign   string
+	DataType string
+	remove   bool
+	Modify   bool
 }
 
-// Create return create sql with the provided tbname and columns
+// RenameColumn struct allows renaming of columns
-func Create(tbname string, columns ...Column) string {
+type RenameColumn struct {
-	return ""
+	OldName     string
+	OldNull     string
+	OldDefault  string
+	OldUnsign   string
+	OldDataType string
+	NewName     string
+	Column
 }
 
-// Drop return the drop sql with the provided tbname and columns
+// NewCol creates a new standard column and attaches it to m struct
-func Drop(tbname string, columns ...Column) string {
+func (m *Migration) NewCol(name string) *Column {
-	return ""
+	col := &Column{Name: name}
+	m.AddColumns(col)
+	return col
 }
 
-// TableDDL is still in think
+//PriCol creates a new primary column and attaches it to m struct
-func TableDDL(tbname string, columns ...Column) string {
+func (m *Migration) PriCol(name string) *Column {
-	return ""
+	col := &Column{Name: name}
+	m.AddColumns(col)
+	m.AddPrimary(col)
+	return col
+}
+
+//UniCol creates / appends columns to specified unique key and attaches it to m struct
+func (m *Migration) UniCol(uni, name string) *Column {
+	col := &Column{Name: name}
+	m.AddColumns(col)
+
+	uniqueOriginal := &Unique{}
+
+	for _, unique := range m.Uniques {
+		if unique.Definition == uni {
+			unique.AddColumnsToUnique(col)
+			uniqueOriginal = unique
+		}
+	}
+	if uniqueOriginal.Definition == "" {
+		unique := &Unique{Definition: uni}
+		unique.AddColumnsToUnique(col)
+		m.AddUnique(unique)
+	}
+
+	return col
+}
+
+//Remove marks the columns to be removed.
+//it allows reverse m to create the column.
+func (c *Column) Remove() {
+	c.remove = true
+}
+
+//SetAuto enables auto_increment of column (can be used once)
+func (c *Column) SetAuto(inc bool) *Column {
+	if inc {
+		c.Inc = "auto_increment"
+	}
+	return c
+}
+
+//SetNullable sets the column to be null
+func (c *Column) SetNullable(null bool) *Column {
+	if null {
+		c.Null = "DEFAULT NULL"
+
+	} else {
+		c.Null = "NOT NULL"
+	}
+	return c
+}
+
+//SetDefault sets the default value, prepend with "DEFAULT "
+func (c *Column) SetDefault(def string) *Column {
+	c.Default = def
+	return c
+}
+
+//SetUnsigned sets the column to be unsigned int
+func (c *Column) SetUnsigned(unsign bool) *Column {
+	if unsign {
+		c.Unsign = "UNSIGNED"
+	}
+	return c
+}
+
+//SetDataType sets the dataType of the column
+func (c *Column) SetDataType(dataType string) *Column {
+	c.DataType = dataType
+	return c
+}
+
+//SetOldNullable allows reverting to previous nullable on reverse ms
+func (c *RenameColumn) SetOldNullable(null bool) *RenameColumn {
+	if null {
+		c.OldNull = "DEFAULT NULL"
+
+	} else {
+		c.OldNull = "NOT NULL"
+	}
+	return c
+}
+
+//SetOldDefault allows reverting to previous default on reverse ms
+func (c *RenameColumn) SetOldDefault(def string) *RenameColumn {
+	c.OldDefault = def
+	return c
+}
+
+//SetOldUnsigned allows reverting to previous unsgined on reverse ms
+func (c *RenameColumn) SetOldUnsigned(unsign bool) *RenameColumn {
+	if unsign {
+		c.OldUnsign = "UNSIGNED"
+	}
+	return c
+}
+
+//SetOldDataType allows reverting to previous datatype on reverse ms
+func (c *RenameColumn) SetOldDataType(dataType string) *RenameColumn {
+	c.OldDataType = dataType
+	return c
+}
+
+//SetPrimary adds the columns to the primary key (can only be used any number of times in only one m)
+func (c *Column) SetPrimary(m *Migration) *Column {
+	m.Primary = append(m.Primary, c)
+	return c
+}
+
+//AddColumnsToUnique adds the columns to Unique Struct
+func (unique *Unique) AddColumnsToUnique(columns ...*Column) *Unique {
+
+	unique.Columns = append(unique.Columns, column...)
+
+	return unique
+}
+
+//AddColumns adds columns to m struct
+func (m *Migration) AddColumns(columns ...*Column) *Migration {
+
+	m.Columns = append(m.Columns, column...)
+
+	return m
+}
+
+//AddPrimary adds the column to primary in m struct
+func (m *Migration) AddPrimary(primary *Column) *Migration {
+	m.Primary = append(m.Primary, primary)
+	return m
+}
+
+//AddUnique adds the column to unique in m struct
+func (m *Migration) AddUnique(unique *Unique) *Migration {
+	m.Uniques = append(m.Uniques, unique)
+	return m
+}
+
+//AddForeign adds the column to foreign in m struct
+func (m *Migration) AddForeign(foreign *Foreign) *Migration {
+	m.Foreigns = append(m.Foreigns, foreign)
+	return m
+}
+
+//AddIndex adds the column to index in m struct
+func (m *Migration) AddIndex(index *Index) *Migration {
+	m.Indexes = append(m.Indexes, index)
+	return m
+}
+
+//RenameColumn allows renaming of columns
+func (m *Migration) RenameColumn(from, to string) *RenameColumn {
+	rename := &RenameColumn{OldName: from, NewName: to}
+	m.Renames = append(m.Renames, rename)
+	return rename
+}
+
+//GetSQL returns the generated sql depending on ModifyType
+func (m *Migration) GetSQL() (sql string) {
+	sql = ""
+	switch m.ModifyType {
+	case "create":
+		{
+			sql += fmt.Sprintf("CREATE TABLE `%s` (", m.TableName)
+			for index, column := range m.Columns {
+				sql += fmt.Sprintf("\n `%s` %s %s %s %s %s", column.Name, column.DataType, column.Unsign, column.Null, column.Inc, column.Default)
+				if len(m.Columns) > index+1 {
+					sql += ","
+				}
+			}
+
+			if len(m.Primary) > 0 {
+				sql += fmt.Sprintf(",\n PRIMARY KEY( ")
+			}
+			for index, column := range m.Primary {
+				sql += fmt.Sprintf(" `%s`", column.Name)
+				if len(m.Primary) > index+1 {
+					sql += ","
+				}
+
+			}
+			if len(m.Primary) > 0 {
+				sql += fmt.Sprintf(")")
+			}
+
+			for _, unique := range m.Uniques {
+				sql += fmt.Sprintf(",\n UNIQUE KEY `%s`( ", unique.Definition)
+				for index, column := range unique.Columns {
+					sql += fmt.Sprintf(" `%s`", column.Name)
+					if len(unique.Columns) > index+1 {
+						sql += ","
+					}
+				}
+				sql += fmt.Sprintf(")")
+			}
+			sql += fmt.Sprintf(")ENGINE=%s DEFAULT CHARSET=%s;", m.Engine, m.Charset)
+			break
+		}
+	case "alter":
+		{
+			sql += fmt.Sprintf("ALTER TABLE `%s` ", m.TableName)
+			for index, column := range m.Columns {
+				if !column.remove {
+					beego.BeeLogger.Info("col")
+					sql += fmt.Sprintf("\n ADD `%s` %s %s %s %s %s", column.Name, column.DataType, column.Unsign, column.Null, column.Inc, column.Default)
+				} else {
+					sql += fmt.Sprintf("\n DROP COLUMN `%s`", column.Name)
+				}
+
+				if len(m.Columns) > index+1 {
+					sql += ","
+				}
+			}
+			for index, column := range m.Renames {
+				sql += fmt.Sprintf(",\n CHANGE COLUMN `%s` `%s` %s %s %s %s %s", column.OldName, column.NewName, column.DataType, column.Unsign, column.Null, column.Inc, column.Default)
+				if len(m.Renames) > index+1 {
+					sql += ","
+				}
+			}
+
+			sql += ";"
+
+			break
+		}
+	case "reverse":
+		{
+
+			sql += fmt.Sprintf("ALTER TABLE `%s`", m.TableName)
+			for index, column := range m.Columns {
+				if column.remove {
+					sql += fmt.Sprintf("\n ADD `%s` %s %s %s %s %s", column.Name, column.DataType, column.Unsign, column.Null, column.Inc, column.Default)
+				} else {
+					sql += fmt.Sprintf("\n DROP COLUMN `%s`", column.Name)
+				}
+				if len(m.Columns) > index+1 {
+					sql += ","
+				}
+			}
+
+			if len(m.Primary) > 0 {
+				sql += fmt.Sprintf(",\n DROP PRIMARY KEY")
+			}
+
+			for index, unique := range m.Uniques {
+				sql += fmt.Sprintf(",\n DROP KEY `%s`", unique.Definition)
+				if len(m.Uniques) > index+1 {
+					sql += ","
+				}
+
+			}
+			for index, column := range m.Renames {
+				sql += fmt.Sprintf(",\n CHANGE COLUMN `%s` `%s` %s %s %s %s", column.NewName, column.OldName, column.OldDataType, column.OldUnsign, column.OldNull, column.OldDefault)
+				if len(m.Renames) > index+1 {
+					sql += ","
+				}
+			}
+			sql += ";"
+		}
+	case "delete":
+		{
+			sql += fmt.Sprintf("DROP TABLE IF EXISTS `%s`;", m.TableName)
+		}
+	}
+
+	return
 }

migration/migration.go

@@ -52,6 +52,25 @@ type Migrationer interface {
 	GetCreated() int64
 }
 
+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
 )
@@ -60,12 +79,6 @@ 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() {
 
@@ -76,6 +89,11 @@ func (m *Migration) Down() {
 
 }
 
+func (m *Migration) Migrate(migrationType string) {
+	m.ModifyType = migrationType
+	m.sqls = append(m.sqls, m.GetSQL())
+}
+
 // SQL add sql want to execute
 func (m *Migration) SQL(sql string) {
 	m.sqls = append(m.sqls, sql)