Recognize GROUPING() as a aggregate expression.

Previously GROUPING() was not recognized as a aggregate expression,
erroneously allowing the planner to move it from HAVING to WHERE.

Author: Jeevan Chalke
Reviewed-By: Andrew Gierth
Discussion: CAM2+6=WG9omG5rFOMAYBweJxmpTaapvVp5pCeMrE6BfpCwr4Og@mail.gmail.com
Backpatch: 9.5, where grouping sets were introduced

src/backend/optimizer/util/clauses.c

@@ -390,7 +390,7 @@ make_ands_implicit(Expr *clause)
 
 /*
  * contain_agg_clause
- *	  Recursively search for Aggref nodes within a clause.
+ *	  Recursively search for Aggref/GroupingFunc nodes within a clause.
  *
  *	  Returns true if any aggregate found.
  *
@@ -417,6 +417,11 @@ contain_agg_clause_walker(Node *node, void *context)
 		Assert(((Aggref *) node)->agglevelsup == 0);
 		return true;			/* abort the tree traversal and return true */
 	}
+	if (IsA(node, GroupingFunc))
+	{
+		Assert(((GroupingFunc *) node)->agglevelsup == 0);
+		return true;			/* abort the tree traversal and return true */
+	}
 	Assert(!IsA(node, SubLink));
 	return expression_tree_walker(node, contain_agg_clause_walker, context);
 }

src/test/regress/expected/groupingsets.out

@@ -486,6 +486,68 @@ having exists (select 1 from onek b where sum(distinct a.four) = b.four);
    9 |   3
 (25 rows)
 
+-- HAVING with GROUPING queries
+select ten, grouping(ten) from onek
+group by grouping sets(ten) having grouping(ten) >= 0
+order by 2,1;
+ ten | grouping 
+-----+----------
+   0 |        0
+   1 |        0
+   2 |        0
+   3 |        0
+   4 |        0
+   5 |        0
+   6 |        0
+   7 |        0
+   8 |        0
+   9 |        0
+(10 rows)
+
+select ten, grouping(ten) from onek
+group by grouping sets(ten, four) having grouping(ten) > 0
+order by 2,1;
+ ten | grouping 
+-----+----------
+     |        1
+     |        1
+     |        1
+     |        1
+(4 rows)
+
+select ten, grouping(ten) from onek
+group by rollup(ten) having grouping(ten) > 0
+order by 2,1;
+ ten | grouping 
+-----+----------
+     |        1
+(1 row)
+
+select ten, grouping(ten) from onek
+group by cube(ten) having grouping(ten) > 0
+order by 2,1;
+ ten | grouping 
+-----+----------
+     |        1
+(1 row)
+
+select ten, grouping(ten) from onek
+group by (ten) having grouping(ten) >= 0
+order by 2,1;
+ ten | grouping 
+-----+----------
+   0 |        0
+   1 |        0
+   2 |        0
+   3 |        0
+   4 |        0
+   5 |        0
+   6 |        0
+   7 |        0
+   8 |        0
+   9 |        0
+(10 rows)
+
 -- FILTER queries
 select ten, sum(distinct four) filter (where four::text ~ '123') from onek a
 group by rollup(ten);

src/test/regress/sql/groupingsets.sql

@@ -154,6 +154,23 @@ select ten, sum(distinct four) from onek a
 group by grouping sets((ten,four),(ten))
 having exists (select 1 from onek b where sum(distinct a.four) = b.four);
 
+-- HAVING with GROUPING queries
+select ten, grouping(ten) from onek
+group by grouping sets(ten) having grouping(ten) >= 0
+order by 2,1;
+select ten, grouping(ten) from onek
+group by grouping sets(ten, four) having grouping(ten) > 0
+order by 2,1;
+select ten, grouping(ten) from onek
+group by rollup(ten) having grouping(ten) > 0
+order by 2,1;
+select ten, grouping(ten) from onek
+group by cube(ten) having grouping(ten) > 0
+order by 2,1;
+select ten, grouping(ten) from onek
+group by (ten) having grouping(ten) >= 0
+order by 2,1;
+
 -- FILTER queries
 select ten, sum(distinct four) filter (where four::text ~ '123') from onek a
 group by rollup(ten);