Merge pull request #754 from erizocosmico/fix/error-count-distinct

sql/parse: error for unsupported distinct on aggregations

engine_test.go

@@ -1026,7 +1026,7 @@ var queries = []struct {
 		FROM (
 			SELECT
 				i,
-				COUNT(DISTINCT s) AS foo
+				COUNT(s) AS foo
 			FROM mytable
 			GROUP BY i
 		) AS q

sql/parse/parse.go

@@ -10,11 +10,11 @@ import (
 	"strings"
 
 	opentracing "github.com/opentracing/opentracing-go"
-	"gopkg.in/src-d/go-errors.v1"
 	"github.com/src-d/go-mysql-server/sql"
 	"github.com/src-d/go-mysql-server/sql/expression"
 	"github.com/src-d/go-mysql-server/sql/expression/function"
 	"github.com/src-d/go-mysql-server/sql/plan"
+	"gopkg.in/src-d/go-errors.v1"
 	"vitess.io/vitess/go/vt/sqlparser"
 )
 
@@ -765,6 +765,10 @@ func exprToExpression(e sqlparser.Expr) (sql.Expression, error) {
 			return nil, err
 		}
 
+		if v.Distinct {
+			return nil, ErrUnsupportedSyntax.New("DISTINCT on aggregations")
+		}
+
 		return expression.NewUnresolvedFunction(v.Name.Lowered(),
 			v.IsAggregate(), exprs...), nil
 	case *sqlparser.ParenExpr:

sql/parse/parse_test.go

@@ -3,12 +3,12 @@ package parse
 import (
 	"testing"
 
-	errors "gopkg.in/src-d/go-errors.v1"
 	"github.com/src-d/go-mysql-server/sql/expression"
 	"github.com/src-d/go-mysql-server/sql/plan"
+	errors "gopkg.in/src-d/go-errors.v1"
 
-	"github.com/stretchr/testify/require"
 	"github.com/src-d/go-mysql-server/sql"
+	"github.com/stretchr/testify/require"
 )
 
 var fixtures = map[string]sql.Node{
@@ -1166,6 +1166,7 @@ var fixturesErrors = map[string]*errors.Kind{
 	`SELECT '2018-05-01' / INTERVAL 1 DAY`:                    ErrUnsupportedSyntax,
 	`SELECT INTERVAL 1 DAY + INTERVAL 1 DAY`:                  ErrUnsupportedSyntax,
 	`SELECT '2018-05-01' + (INTERVAL 1 DAY + INTERVAL 1 DAY)`: ErrUnsupportedSyntax,
+	`SELECT COUNT(DISTINCT foo) FROM b`:                       ErrUnsupportedSyntax,
 }
 
 func TestParseErrors(t *testing.T) {