Add test for AlterColumn

dialects/mssql/migrator.go

@@ -71,6 +71,18 @@ func (m Migrator) HasColumn(value interface{}, field string) bool {
 	return count > 0
 }
 
+func (m Migrator) AlterColumn(value interface{}, field string) error {
+	return m.RunWithValue(value, func(stmt *gorm.Statement) error {
+		if field := stmt.Schema.LookUpField(field); field != nil {
+			return m.DB.Exec(
+				"ALTER TABLE ? ALTER COLUMN ? ?",
+				clause.Table{Name: stmt.Table}, clause.Column{Name: field.DBName}, m.FullDataTypeOf(field),
+			).Error
+		}
+		return fmt.Errorf("failed to look up field with name: %s", field)
+	})
+}
+
 func (m Migrator) RenameColumn(value interface{}, oldName, newName string) error {
 	return m.RunWithValue(value, func(stmt *gorm.Statement) error {
 		if field := stmt.Schema.LookUpField(oldName); field != nil {

dialects/mysql/migrator.go

@@ -16,8 +16,8 @@ func (m Migrator) AlterColumn(value interface{}, field string) error {
 	return m.RunWithValue(value, func(stmt *gorm.Statement) error {
 		if field := stmt.Schema.LookUpField(field); field != nil {
 			return m.DB.Exec(
-				"ALTER TABLE ? MODIFY COLUMN ? TYPE ?",
+				"ALTER TABLE ? MODIFY COLUMN ? ?",
-				clause.Table{Name: stmt.Table}, clause.Column{Name: field.DBName}, clause.Expr{SQL: field.DBDataType},
+				clause.Table{Name: stmt.Table}, clause.Column{Name: field.DBName}, m.FullDataTypeOf(field),
 			).Error
 		}
 		return fmt.Errorf("failed to look up field with name: %s", field)

dialects/postgres/postgres.go

@@ -89,7 +89,7 @@ func (dialector Dialector) DataTypeOf(field *schema.Field) string {
 		}
 		return "text"
 	case schema.Time:
-		return "timestamp with time zone"
+		return "timestamptz"
 	case schema.Bytes:
 		return "bytea"
 	}

dialects/sqlite/migrator.go

@@ -38,6 +38,42 @@ func (m Migrator) HasColumn(value interface{}, name string) bool {
 	return count > 0
 }
 
+func (m Migrator) AlterColumn(value interface{}, name string) error {
+	return m.RunWithValue(value, func(stmt *gorm.Statement) error {
+		if field := stmt.Schema.LookUpField(name); field != nil {
+			var (
+				createSQL    string
+				newTableName = stmt.Table + "__temp"
+			)
+
+			m.DB.Raw("SELECT sql FROM sqlite_master WHERE type = ? AND tbl_name = ? AND name = ?", "table", stmt.Table, stmt.Table).Row().Scan(&createSQL)
+
+			if reg, err := regexp.Compile("(`|'|\"| )" + name + "(`|'|\"| ) .*?,"); err == nil {
+				tableReg, err := regexp.Compile(" ('|`|\"| )" + stmt.Table + "('|`|\"| ) ")
+				if err != nil {
+					return err
+				}
+
+				createSQL = tableReg.ReplaceAllString(createSQL, fmt.Sprintf(" `%v` ", newTableName))
+				createSQL = reg.ReplaceAllString(createSQL, "?")
+
+				var columns []string
+				columnTypes, _ := m.DB.Migrator().ColumnTypes(value)
+				for _, columnType := range columnTypes {
+					columns = append(columns, fmt.Sprintf("`%v`", columnType.Name()))
+				}
+
+				createSQL = fmt.Sprintf("PRAGMA foreign_keys=off;BEGIN TRANSACTION;"+createSQL+";INSERT INTO `%v`(%v) SELECT %v FROM `%v`;DROP TABLE `%v`;ALTER TABLE `%v` RENAME TO `%v`;COMMIT;", newTableName, strings.Join(columns, ","), strings.Join(columns, ","), stmt.Table, stmt.Table, newTableName, stmt.Table)
+				return m.DB.Exec(createSQL, m.FullDataTypeOf(field)).Error
+			} else {
+				return err
+			}
+		} else {
+			return fmt.Errorf("failed to alter field with name %v", name)
+		}
+	})
+}
+
 func (m Migrator) DropColumn(value interface{}, name string) error {
 	return m.RunWithValue(value, func(stmt *gorm.Statement) error {
 		if field := stmt.Schema.LookUpField(name); field != nil {

migrator/migrator.go

@@ -283,7 +283,7 @@ func (m Migrator) AlterColumn(value interface{}, field string) error {
 		if field := stmt.Schema.LookUpField(field); field != nil {
 			return m.DB.Exec(
 				"ALTER TABLE ? ALTER COLUMN ? TYPE ?",
-				clause.Table{Name: stmt.Table}, clause.Column{Name: field.DBName}, clause.Expr{SQL: m.DataTypeOf(field)},
+				clause.Table{Name: stmt.Table}, clause.Column{Name: field.DBName}, m.FullDataTypeOf(field),
 			).Error
 		}
 		return fmt.Errorf("failed to look up field with name: %s", field)

tests/migrate_test.go

@@ -2,6 +2,7 @@ package tests_test
 
 import (
 	"math/rand"
+	"strings"
 	"testing"
 	"time"
 
@@ -124,6 +125,31 @@ func TestColumns(t *testing.T) {
 		t.Errorf("Failed to migrate, got %v", err)
 	}
 
+	type ColumnStruct2 struct {
+		gorm.Model
+		Name string `gorm:"size:100"`
+	}
+
+	if err := DB.Table("column_structs").Migrator().AlterColumn(&ColumnStruct2{}, "Name"); err != nil {
+		t.Fatalf("no error should happend when alter column, but got %v", err)
+	}
+
+	if columnTypes, err := DB.Migrator().ColumnTypes(&ColumnStruct{}); err != nil {
+		t.Fatalf("no error should returns for ColumnTypes")
+	} else {
+		stmt := &gorm.Statement{DB: DB}
+		stmt.Parse(&ColumnStruct2{})
+
+		for _, columnType := range columnTypes {
+			if columnType.Name() == "name" {
+				dataType := DB.Dialector.DataTypeOf(stmt.Schema.LookUpField(columnType.Name()))
+				if !strings.Contains(strings.ToUpper(dataType), strings.ToUpper(columnType.DatabaseTypeName())) {
+					t.Errorf("column type should be correct, name: %v, length: %v, expects: %v", columnType.Name(), columnType.DatabaseTypeName(), dataType)
+				}
+			}
+		}
+	}
+
 	type NewColumnStruct struct {
 		gorm.Model
 		Name    string