[parser] parser: implement Restore for ExistsSubqueryExpr (#126)

parser/ast/expressions.go

@@ -588,7 +588,15 @@ type ExistsSubqueryExpr struct {
 
 // Restore implements Node interface.
 func (n *ExistsSubqueryExpr) Restore(ctx *RestoreCtx) error {
-	return errors.New("Not implemented")
+	if n.Not {
+		ctx.WriteKeyWord("NOT EXISTS ")
+	} else {
+		ctx.WriteKeyWord("EXISTS ")
+	}
+	if err := n.Sel.Restore(ctx); err != nil {
+		return errors.Annotate(err, "An error occurred while restore ExistsSubqueryExpr.Sel")
+	}
+	return nil
 }
 
 // Format the ExprNode into a Writer.

parser/ast/expressions_test.go

@@ -324,6 +324,18 @@ func (tc *testExpressionsSuite) TestPositionExprRestore(c *C) {
 		return node.(*SelectStmt).OrderBy.Items[0]
 	}
 	RunNodeRestoreTest(c, testCases, "select * from t order by %s", extractNodeFunc)
+
+}
+
+func (tc *testExpressionsSuite) TestExistsSubqueryExprRestore(c *C) {
+	testCases := []NodeRestoreTestCase{
+		{"EXISTS (SELECT 2)", "EXISTS (SELECT 2)"},
+		{"NOT EXISTS (SELECT 2)", "NOT EXISTS (SELECT 2)"},
+	}
+	extractNodeFunc := func(node Node) Node {
+		return node.(*SelectStmt).Where
+	}
+	RunNodeRestoreTest(c, testCases, "select 1 from t1 where %s", extractNodeFunc)
 }
 
 func (tc *testExpressionsSuite) TestVariableExpr(c *C) {