parser : support drop sequence syntax. (#680)

Author: AilinKid

ast/ddl.go

@@ -33,6 +33,7 @@ var (
 	_ DDLNode = &DropDatabaseStmt{}
 	_ DDLNode = &DropIndexStmt{}
 	_ DDLNode = &DropTableStmt{}
+	_ DDLNode = &DropSequenceStmt{}
 	_ DDLNode = &RenameTableStmt{}
 	_ DDLNode = &TruncateTableStmt{}
 	_ DDLNode = &RepairTableStmt{}
@@ -1089,6 +1090,54 @@ func (n *DropTableStmt) Accept(v Visitor) (Node, bool) {
 	return v.Leave(n)
 }
 
+// DropSequenceStmt is a statement to drop a Sequence.
+type DropSequenceStmt struct {
+	ddlNode
+
+	IfExists    bool
+	Sequences   []*TableName
+	IsTemporary bool
+}
+
+// Restore implements Node interface.
+func (n *DropSequenceStmt) Restore(ctx *RestoreCtx) error {
+	if n.IsTemporary {
+		ctx.WriteKeyWord("DROP TEMPORARY SEQUENCE ")
+	} else {
+		ctx.WriteKeyWord("DROP SEQUENCE ")
+	}
+	if n.IfExists {
+		ctx.WriteKeyWord("IF EXISTS ")
+	}
+	for i, sequence := range n.Sequences {
+		if i != 0 {
+			ctx.WritePlain(", ")
+		}
+		if err := sequence.Restore(ctx); err != nil {
+			return errors.Annotatef(err, "An error occurred while restore DropSequenceStmt.Sequences[%d]", i)
+		}
+	}
+
+	return nil
+}
+
+// Accept implements Node Accept interface.
+func (n *DropSequenceStmt) Accept(v Visitor) (Node, bool) {
+	newNode, skipChildren := v.Enter(n)
+	if skipChildren {
+		return v.Leave(newNode)
+	}
+	n = newNode.(*DropSequenceStmt)
+	for i, val := range n.Sequences {
+		node, ok := val.Accept(v)
+		if !ok {
+			return n, false
+		}
+		n.Sequences[i] = node.(*TableName)
+	}
+	return v.Leave(n)
+}
+
 // RenameTableStmt is a statement to rename a table.
 // See http://dev.mysql.com/doc/refman/5.7/en/rename-table.html
 type RenameTableStmt struct {

ast/ddl_test.go

@@ -531,7 +531,7 @@ func (ts *testDDLSuite) TestAdminRepairTableRestore(c *C) {
 	RunNodeRestoreTest(c, testCases, "%s", extractNodeFunc)
 }
 
-func (ts *testDDLSuite) TestCreateSequenceRestore(c *C) {
+func (ts *testDDLSuite) TestSequenceRestore(c *C) {
 	testCases := []NodeRestoreTestCase{
 		{"create sequence seq", "CREATE SEQUENCE `seq`"},
 		{"create sequence if not exists seq", "CREATE SEQUENCE IF NOT EXISTS `seq`"},
@@ -564,6 +564,13 @@ func (ts *testDDLSuite) TestCreateSequenceRestore(c *C) {
 		{"create temporary sequence seq nocycle nocache maxvalue 1000 cache 1", "CREATE TEMPORARY SEQUENCE `seq` NOCYCLE NOCACHE MAXVALUE 1000 CACHE 1"},
 		{"create temporary sequence seq increment -1 no minvalue no maxvalue cache = 1", "CREATE TEMPORARY SEQUENCE `seq` INCREMENT BY -1 NO MINVALUE NO MAXVALUE CACHE 1"},
 		{"create temporary sequence if not exists seq increment 1 minvalue 0 nomaxvalue cache 100 nocycle noorder", "CREATE TEMPORARY SEQUENCE IF NOT EXISTS `seq` INCREMENT BY 1 MINVALUE 0 NO MAXVALUE CACHE 100 NOCYCLE NOORDER"},
+
+		// test drop sequence
+		{"drop sequence seq", "DROP SEQUENCE `seq`"},
+		{"drop sequence seq, seq2", "DROP SEQUENCE `seq`, `seq2`"},
+		{"drop sequence if exists seq, seq2", "DROP SEQUENCE IF EXISTS `seq`, `seq2`"},
+		{"drop temporary sequence if exists seq", "DROP TEMPORARY SEQUENCE IF EXISTS `seq`"},
+		{"drop temporary sequence sequence", "DROP TEMPORARY SEQUENCE `sequence`"},
 	}
 	extractNodeFunc := func(node Node) Node {
 		return node