Division by zero in planner.c:grouping_planner()

Hello,

with the change below, make installcheck fails -- at the updatable_views
step, I believe. Apparently it's the "SELECT * FROM v1 WHERE a=3;" that
triggers this.

diff --git a/src/backend/optimizer/plan/planner.c
b/src/backend/optimizer/plan/planner.c
index 6ee411e..cbdee7c 100644
--- a/src/backend/optimizer/plan/planner.c
+++ b/src/backend/optimizer/plan/planner.c
@@ -1661,6 +1661,7 @@ grouping_planner(PlannerInfo *root, double
tuple_fraction)
* Plain non-grouped, non-aggregated query: an
absolute tuple
* fraction can be divided by the number of tuples.
*/
+ Assert(path_rows != 0);
if (tuple_fraction >= 1.0)
tuple_fraction /= path_rows;
}