Merge pull request #1 from pingcap/master

Merge pull request from pingcap/tidb

ast/ast.go

@@ -0,0 +1,81 @@
+// Copyright 2015 PingCAP, Inc.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+// Package ast is the abstract syntax tree parsed from a SQL statement by parser.
+// It can be analysed and transformed by optimizer.
+package ast
+
+import (
+	"github.com/pingcap/tidb/util/types"
+)
+
+// Node is the basic element of the AST.
+// Interfaces embed Node should have 'Node' name suffix.
+type Node interface {
+	// Accept accepts Visitor to visit itself.
+	// The returned node should replace original node.
+	// ok returns false to stop visiting.
+	Accept(v Visitor) (node Node, ok bool)
+	// Text returns the original text of the element.
+	Text() string
+	// SetText sets original text to the Node.
+	SetText(text string)
+}
+
+// ExprNode is a node that can be evaluated.
+// Name of implementations should have 'Expr' suffix.
+type ExprNode interface {
+	// Node is embeded in ExprNode.
+	Node
+	// IsStatic means it can be evaluated independently.
+	IsStatic() bool
+	// SetType sets evaluation type to the expression.
+	SetType(tp *types.FieldType)
+	// GetType gets the evaluation type of the expression.
+	GetType() *types.FieldType
+}
+
+// FuncNode represents function call expression node.
+type FuncNode interface {
+	ExprNode
+	functionExpression()
+}
+
+// StmtNode represents statement node.
+// Name of implementations should have 'Stmt' suffix.
+type StmtNode interface {
+	Node
+	statement()
+}
+
+// DDLNode represents DDL statement node.
+type DDLNode interface {
+	StmtNode
+	ddlStatement()
+}
+
+// DMLNode represents DML statement node.
+type DMLNode interface {
+	StmtNode
+	dmlStatement()
+}
+
+// Visitor visits a Node.
+type Visitor interface {
+	// VisitEnter is called before children nodes is visited.
+	// ok returns false to stop visiting.
+	Enter(n Node) (ok bool)
+	// VisitLeave is called after children nodes has been visited.
+	// ok returns false to stop visiting.
+	Leave(n Node) (node Node, ok bool)
+}

ast/base.go

@@ -0,0 +1,88 @@
+// Copyright 2015 PingCAP, Inc.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package ast
+
+import "github.com/pingcap/tidb/util/types"
+
+// node is the struct implements node interface except for Accept method.
+// Node implementations should embed it in.
+type node struct {
+	text string
+}
+
+// SetText implements Node interface.
+func (n *node) SetText(text string) {
+	n.text = text
+}
+
+// Text implements Node interface.
+func (n *node) Text() string {
+	return n.text
+}
+
+// stmtNode implements StmtNode interface.
+// Statement implementations should embed it in.
+type stmtNode struct {
+	node
+}
+
+// statement implements StmtNode interface.
+func (sn *stmtNode) statement() {}
+
+// ddlNode implements DDLNode interface.
+// DDL implementations should embed it in.
+type ddlNode struct {
+	stmtNode
+}
+
+// ddlStatement implements DDLNode interface.
+func (dn *ddlNode) ddlStatement() {}
+
+// dmlNode is the struct implements DMLNode interface.
+// DML implementations should embed it in.
+type dmlNode struct {
+	stmtNode
+}
+
+// dmlStatement implements DMLNode interface.
+func (dn *dmlNode) dmlStatement() {}
+
+// expressionNode is the struct implements Expression interface.
+// Expression implementations should embed it in.
+type exprNode struct {
+	node
+	tp *types.FieldType
+}
+
+// IsStatic implements Expression interface.
+func (en *exprNode) IsStatic() bool {
+	return false
+}
+
+// SetType implements Expression interface.
+func (en *exprNode) SetType(tp *types.FieldType) {
+	en.tp = tp
+}
+
+// GetType implements Expression interface.
+func (en *exprNode) GetType() *types.FieldType {
+	return en.tp
+}
+
+type funcNode struct {
+	exprNode
+}
+
+// FunctionExpression implements FounctionNode interface.
+func (fn *funcNode) functionExpression() {}