check if fields are valid during parse.

Binary expressions that yield a boolean are invalid and we can catch
these at parse time.

Fixes influxdata#3525

CHANGELOG.md

@@ -14,6 +14,7 @@
 - [#3420](https://github.com/influxdb/influxdb/pull/3420): Catch opentsdb malformed tags. Thanks @nathanielc.
 - [#3404](https://github.com/influxdb/influxdb/pull/3404): Added support for escaped single quotes in query string. Thanks @jhorwit2
 - [#3414](https://github.com/influxdb/influxdb/issues/3414): Shard mappers perform query re-writing
+- [#3525](https://github.com/influxdb/influxdb/pull/3525): check if fields are valid during parse time.
 
 ## v0.9.2 [2015-07-24]
 

influxql/parser.go

@@ -1471,11 +1471,18 @@ func (p *Parser) parseFields() (Fields, error) {
 func (p *Parser) parseField() (*Field, error) {
 	f := &Field{}
 
+	_, pos, _ := p.scanIgnoreWhitespace()
+	p.unscan()
 	// Parse the expression first.
 	expr, err := p.ParseExpr()
 	if err != nil {
 		return nil, err
 	}
+	var c validateField
+	Walk(&c, expr)
+	if c.foundInvalid {
+		return nil, fmt.Errorf("invalid operator %s in SELECT clause at line %d, char %d; operator is intended for WHERE clause", c.badToken, pos.Line+1, pos.Char+1)
+	}
 	f.Expr = expr
 
 	// Parse the alias if the current and next tokens are "WS AS".
@@ -1491,6 +1498,30 @@ func (p *Parser) parseField() (*Field, error) {
 	return f, nil
 }
 
+// validateField checks if the Expr is a valid field. We disallow all binary expression
+// that return a boolean
+type validateField struct {
+	foundInvalid bool
+	badToken     Token
+}
+
+func (c *validateField) Visit(n Node) Visitor {
+	e, ok := n.(*BinaryExpr)
+	if !ok {
+		return c
+	}
+
+	switch e.Op {
+	case EQ, NEQ, EQREGEX,
+		NEQREGEX, LT, LTE, GT, GTE,
+		AND, OR:
+		c.foundInvalid = true
+		c.badToken = e.Op
+		return nil
+	}
+	return c
+}
+
 // parseAlias parses the "AS (IDENT|STRING)" alias for fields and dimensions.
 func (p *Parser) parseAlias() (string, error) {
 	// Check if the next token is "AS". If not, then unscan and exit.

influxql/parser_test.go

@@ -1244,6 +1244,9 @@ func TestParser_ParseStatement(t *testing.T) {
 		{s: `select derivative() from myseries`, err: `invalid number of arguments for derivative, expected at least 1 but no more than 2, got 0`},
 		{s: `select derivative(mean(value), 1h, 3) from myseries`, err: `invalid number of arguments for derivative, expected at least 1 but no more than 2, got 3`},
 		{s: `SELECT field1 from myseries WHERE host =~ 'asd' LIMIT 1`, err: `found asd, expected regex at line 1, char 42`},
+		{s: `SELECT value > 2 FROM cpu`, err: `invalid operator > in SELECT clause at line 1, char 8; operator is intended for WHERE clause`},
+		{s: `SELECT value = 2 FROM cpu`, err: `invalid operator = in SELECT clause at line 1, char 8; operator is intended for WHERE clause`},
+		{s: `SELECT s =~ /foo/ FROM cpu`, err: `invalid operator =~ in SELECT clause at line 1, char 8; operator is intended for WHERE clause`},
 		{s: `DELETE`, err: `found EOF, expected FROM at line 1, char 8`},
 		{s: `DELETE FROM`, err: `found EOF, expected identifier at line 1, char 13`},
 		{s: `DELETE FROM myseries WHERE`, err: `found EOF, expected identifier, string, number, bool at line 1, char 28`},