add drop index sql and modify column sql interface

dialect.go

@@ -58,6 +58,9 @@ type Dialect interface {
 	CreateTableSql(table *Table, tableName, storeEngine, charset string) string
 	DropTableSql(tableName string) string
 	CreateIndexSql(tableName string, index *Index) string
+	DropIndexSql(tableName string, index *Index) string
+
+	ModifyColumnSql(tableName string, col *Column) string
 
 	GetColumns(tableName string) ([]string, map[string]*Column, error)
 	GetTables() ([]*Table, error)
@@ -175,6 +178,26 @@ func (db *Base) CreateIndexSql(tableName string, index *Index) string {
 		quote(strings.Join(index.Cols, quote(","))))
 }
 
+func (db *Base) DropIndexSql(tableName string, index *Index) string {
+	quote := db.Quote
+	//var unique string
+	var idxName string = index.Name
+	if !strings.HasPrefix(idxName, "UQE_") &&
+		!strings.HasPrefix(idxName, "IDX_") {
+		if index.Type == UniqueType {
+			idxName = fmt.Sprintf("UQE_%v_%v", tableName, index.Name)
+		} else {
+			idxName = fmt.Sprintf("IDX_%v_%v", tableName, index.Name)
+		}
+	}
+	return fmt.Sprintf("DROP INDEX %v ON %s",
+		quote(idxName), quote(tableName))
+}
+
+func (db *Base) ModifyColumnSql(tableName string, col *Column) string {
+	return fmt.Sprintf("alter table %s MODIFY COLUMN %s", tableName, col.StringNoPk(db.dialect))
+}
+
 func (b *Base) CreateTableSql(table *Table, tableName, storeEngine, charset string) string {
 	var sql string
 	sql = "CREATE TABLE IF NOT EXISTS "

index.go

@@ -1,5 +1,9 @@
 package core
 
+import (
+	"sort"
+)
+
 const (
 	IndexType = iota + 1
 	UniqueType
@@ -19,6 +23,21 @@ func (index *Index) AddColumn(cols ...string) {
 	}
 }
 
+func (index *Index) Equal(dst *Index) bool {
+	if len(index.Cols) != len(dst.Cols) {
+		return false
+	}
+	sort.StringSlice(index.Cols).Sort()
+	sort.StringSlice(dst.Cols).Sort()
+
+	for i := 0; i < len(index.Cols); i++ {
+		if index.Cols[i] != dst.Cols[i] {
+			return false
+		}
+	}
+	return true
+}
+
 // new an index
 func NewIndex(name string, indexType int) *Index {
 	return &Index{name, indexType, make([]string, 0)}