From 4992a006e4f958b344af67fe4b99c10e7f6905cb Mon Sep 17 00:00:00 2001
From: Ben Johnson <benbjohnson@yahoo.com>
Date: Mon, 24 Nov 2014 23:12:32 -0700
Subject: [PATCH] Add ParenExpr.

---
 influxql/ast.go         | 10 ++++++++++
 influxql/parser.go      | 16 ++++++++++++++++
 influxql/parser_test.go | 22 +++++++++++++++++++---
 3 files changed, 45 insertions(+), 3 deletions(-)

diff --git a/influxql/ast.go b/influxql/ast.go
index 59c9add9de..f60935e58f 100644
--- a/influxql/ast.go
+++ b/influxql/ast.go
@@ -46,6 +46,7 @@ func (_ *BooleanLiteral) node()  {}
 func (_ *TimeLiteral) node()     {}
 func (_ *DurationLiteral) node() {}
 func (_ *BinaryExpr) node()      {}
+func (_ *ParenExpr) node()       {}
 
 // Query represents a collection of order statements.
 type Query struct {
@@ -83,6 +84,7 @@ func (_ *BooleanLiteral) expr()  {}
 func (_ *TimeLiteral) expr()     {}
 func (_ *DurationLiteral) expr() {}
 func (_ *BinaryExpr) expr()      {}
+func (_ *ParenExpr) expr()       {}
 
 // Source represents a source of data for a statement.
 type Source interface {
@@ -227,6 +229,11 @@ type BinaryExpr struct {
 	RHS Expr
 }
 
+// ParenExpr represents a parenthesized expression.
+type ParenExpr struct {
+	Expr Expr
+}
+
 // Visitor can be called by Walk to traverse an AST hierarchy.
 // The Visit() function is called once per node.
 type Visitor interface {
@@ -274,6 +281,9 @@ func Walk(v Visitor, node Node) {
 		Walk(v, n.LHS)
 		Walk(v, n.RHS)
 
+	case *ParenExpr:
+		Walk(v, n.Expr)
+
 	case *Call:
 		for _, expr := range n.Args {
 			Walk(v, expr)
diff --git a/influxql/parser.go b/influxql/parser.go
index 7f134d6f1c..8dfcb977bc 100644
--- a/influxql/parser.go
+++ b/influxql/parser.go
@@ -487,6 +487,22 @@ func (p *Parser) ParseExpr() (Expr, error) {
 
 // parseUnaryExpr parses an non-binary expression.
 func (p *Parser) parseUnaryExpr() (Expr, error) {
+	// If the first token is a LPAREN then parse it as its own grouped expression.
+	if tok, _, _ := p.scanIgnoreWhitespace(); tok == LPAREN {
+		expr, err := p.ParseExpr()
+		if err != nil {
+			return nil, err
+		}
+
+		// Expect an RPAREN at the end.
+		if tok, pos, lit := p.scanIgnoreWhitespace(); tok != RPAREN {
+			return nil, newParseError(tokstr(tok, lit), []string{")"}, pos)
+		}
+
+		return &ParenExpr{Expr: expr}, nil
+	}
+	p.unscan()
+
 	// Read next token.
 	tok, pos, lit := p.scanIgnoreWhitespace()
 	switch tok {
diff --git a/influxql/parser_test.go b/influxql/parser_test.go
index d23ec4308a..015e7f8bee 100644
--- a/influxql/parser_test.go
+++ b/influxql/parser_test.go
@@ -216,7 +216,23 @@ func TestParser_ParseExpr(t *testing.T) {
 			},
 		},
 
-		// 8. Complex binary expression.
+		// 8. Binary expression with LHS paren group.
+		{
+			s: `(1 + 2) * 3`,
+			expr: &influxql.BinaryExpr{
+				Op: influxql.MUL,
+				LHS: &influxql.ParenExpr{
+					Expr: &influxql.BinaryExpr{
+						Op:  influxql.ADD,
+						LHS: &influxql.NumberLiteral{Val: 1},
+						RHS: &influxql.NumberLiteral{Val: 2},
+					},
+				},
+				RHS: &influxql.NumberLiteral{Val: 3},
+			},
+		},
+
+		// 9. Complex binary expression.
 		{
 			s: `value + 3 < 30 AND 1 + 2 OR true`,
 			expr: &influxql.BinaryExpr{
@@ -242,7 +258,7 @@ func TestParser_ParseExpr(t *testing.T) {
 			},
 		},
 
-		// 9. Function call (empty)
+		// 10. Function call (empty)
 		{
 			s: `my_func()`,
 			expr: &influxql.Call{
@@ -250,7 +266,7 @@ func TestParser_ParseExpr(t *testing.T) {
 			},
 		},
 
-		// 10. Function call (multi-arg)
+		// 11. Function call (multi-arg)
 		{
 			s: `my_func(1, 2 + 3)`,
 			expr: &influxql.Call{