Fix problem with parallel queries when none partition is selected

Maksim Milyutin · Maksim Milyutin · commit 681aa4326f20 · 2016-11-04T02:40:11.000+03:00
diff --git a/src/pg_pathman.c b/src/pg_pathman.c
@@ -1878,12 +1878,15 @@ set_append_rel_pathlist(PlannerInfo *root, RelOptInfo *rel, Index rti,
 
 			parallel_workers = Max(parallel_workers, path->parallel_workers);
 		}
-		Assert(parallel_workers > 0);
 
-		/* Generate a partial append path. */
-		appendpath = create_append_path(rel, partial_subpaths, NULL,
-										parallel_workers);
-		add_partial_path(rel, (Path *) appendpath);
+		if (parallel_workers > 0)
+		{
+
+			/* Generate a partial append path. */
+			appendpath = create_append_path(rel, partial_subpaths, NULL,
+					parallel_workers);
+			add_partial_path(rel, (Path *) appendpath);
+		}
 	}
 #endif
 
diff --git a/tests/python/partitioning_test.py b/tests/python/partitioning_test.py
@@ -580,6 +580,22 @@ def ordered(obj):
             res_tuples = sorted(map(lambda x: x[0], res_tuples))
             expected = [1, 2, 3, 4, 5]
             self.assertEqual(res_tuples, expected)
+
+            # Check the case when none partition is selected in result plan
+            test_query = 'select * from range_partitioned where i < 1'
+            plan = con.execute('select query_plan(\'%s\')' % test_query)[0][0]
+            expected = json.loads("""
+            [
+               {
+                 "Plan": {
+                   "Node Type": "Result",
+                   "Parallel Aware": false,
+                   "One-Time Filter": "false"
+                 }
+               }
+            ]
+            """)
+            self.assertEqual(ordered(plan), ordered(expected))
             #  import ipdb; ipdb.set_trace()
 
         # Remove all objects for testing
