Set join_collapse_limit default value to the same as used in PostgreS…

src/backend/utils/misc/guc.c

@@ -1706,7 +1706,7 @@ static struct config_int ConfigureNamesInt[] =
 						 "list of no more than this many items would result.")
 		},
 		&join_collapse_limit,
-		20, 1, INT_MAX,
+		13, 1, INT_MAX,
 		NULL, NULL, NULL
 	},
 	{

src/backend/utils/misc/postgresql.conf.sample

@@ -308,7 +308,7 @@ max_prepared_transactions = 250		# can be 0 or more
 
 #cursor_tuple_fraction = 0.1		# range 0.0-1.0
 #from_collapse_limit = 20
-#join_collapse_limit = 20		# 1 disables collapsing of explicit
+#join_collapse_limit = 13		# 1 disables collapsing of explicit
 					# JOIN clauses
 #gp_segments_for_planner = 0     # if 0, actual number of segments is used
 

src/test/regress/expected/bfv_joins.out

@@ -4195,6 +4195,48 @@ cross join lateral
   union
   select a+1, b from t1 where a+1 < 10) x;
 ERROR:  Passing parameters across motion is not supported. (cdbmutate.c:3701)
+-- Check that Postgres Planner can build a plan with 20 joins in reasonable time
+do $$
+begin 
+  for i in 1..20 loop
+    execute 'create table tj' ||  i ||  '(id int) distributed by (id)';
+  end loop; 
+end
+$$;
+set optimizer to off;
+select trunc(extract(epoch from now())) unix_time1 \gset
+select *
+from tj1 
+  join tj2 on tj1.id = tj2.id
+  join tj3 on tj2.id = tj3.id
+  join tj4 on tj3.id = tj4.id
+  join tj5 on tj4.id = tj5.id
+  join tj6 on tj5.id = tj6.id
+  join tj7 on tj6.id = tj7.id
+  join tj8 on tj7.id = tj8.id
+  join tj9 on tj8.id = tj9.id
+  join tj10 on tj9.id = tj10.id
+  join tj11 on tj10.id = tj11.id
+  join tj12 on tj11.id = tj12.id
+  join tj13 on tj12.id = tj13.id
+  join tj14 on tj13.id = tj14.id
+  join tj15 on tj14.id = tj15.id
+  join tj16 on tj15.id = tj16.id
+  join tj17 on tj16.id = tj17.id
+  join tj18 on tj17.id = tj18.id
+  join tj19 on tj18.id = tj19.id
+  join tj20 on tj19.id = tj20.id;
+ id | id | id | id | id | id | id | id | id | id | id | id | id | id | id | id | id | id | id | id 
+----+----+----+----+----+----+----+----+----+----+----+----+----+----+----+----+----+----+----+----
+(0 rows)
+
+select (trunc(extract(epoch from now())) - :unix_time1) < 100 is_ok;
+ is_ok 
+-------
+ t
+(1 row)
+
+reset optimizer;
 -- Clean up. None of the objects we create are very interesting to keep around.
 reset search_path;
 set client_min_messages='warning';

src/test/regress/expected/bfv_joins_optimizer.out

@@ -4188,6 +4188,48 @@ cross join lateral
   union
   select a+1, b from t1 where a+1 < 10) x;
 ERROR:  Passing parameters across motion is not supported. (cdbmutate.c:3701)
+-- Check that Postgres Planner can build a plan with 20 joins in reasonable time
+do $$
+begin 
+  for i in 1..20 loop
+    execute 'create table tj' ||  i ||  '(id int) distributed by (id)';
+  end loop; 
+end
+$$;
+set optimizer to off;
+select trunc(extract(epoch from now())) unix_time1 \gset
+select *
+from tj1 
+  join tj2 on tj1.id = tj2.id
+  join tj3 on tj2.id = tj3.id
+  join tj4 on tj3.id = tj4.id
+  join tj5 on tj4.id = tj5.id
+  join tj6 on tj5.id = tj6.id
+  join tj7 on tj6.id = tj7.id
+  join tj8 on tj7.id = tj8.id
+  join tj9 on tj8.id = tj9.id
+  join tj10 on tj9.id = tj10.id
+  join tj11 on tj10.id = tj11.id
+  join tj12 on tj11.id = tj12.id
+  join tj13 on tj12.id = tj13.id
+  join tj14 on tj13.id = tj14.id
+  join tj15 on tj14.id = tj15.id
+  join tj16 on tj15.id = tj16.id
+  join tj17 on tj16.id = tj17.id
+  join tj18 on tj17.id = tj18.id
+  join tj19 on tj18.id = tj19.id
+  join tj20 on tj19.id = tj20.id;
+ id | id | id | id | id | id | id | id | id | id | id | id | id | id | id | id | id | id | id | id 
+----+----+----+----+----+----+----+----+----+----+----+----+----+----+----+----+----+----+----+----
+(0 rows)
+
+select (trunc(extract(epoch from now())) - :unix_time1) < 100 is_ok;
+ is_ok 
+-------
+ t
+(1 row)
+
+reset optimizer;
 -- Clean up. None of the objects we create are very interesting to keep around.
 reset search_path;
 set client_min_messages='warning';

src/test/regress/sql/bfv_joins.sql

@@ -645,6 +645,45 @@ cross join lateral
   union
   select a+1, b from t1 where a+1 < 10) x;
 
+-- Check that Postgres Planner can build a plan with 20 joins in reasonable time
+do $$
+begin 
+  for i in 1..20 loop
+    execute 'create table tj' ||  i ||  '(id int) distributed by (id)';
+  end loop; 
+end
+$$;
+
+set optimizer to off;
+
+select trunc(extract(epoch from now())) unix_time1 \gset
+
+select *
+from tj1 
+  join tj2 on tj1.id = tj2.id
+  join tj3 on tj2.id = tj3.id
+  join tj4 on tj3.id = tj4.id
+  join tj5 on tj4.id = tj5.id
+  join tj6 on tj5.id = tj6.id
+  join tj7 on tj6.id = tj7.id
+  join tj8 on tj7.id = tj8.id
+  join tj9 on tj8.id = tj9.id
+  join tj10 on tj9.id = tj10.id
+  join tj11 on tj10.id = tj11.id
+  join tj12 on tj11.id = tj12.id
+  join tj13 on tj12.id = tj13.id
+  join tj14 on tj13.id = tj14.id
+  join tj15 on tj14.id = tj15.id
+  join tj16 on tj15.id = tj16.id
+  join tj17 on tj16.id = tj17.id
+  join tj18 on tj17.id = tj18.id
+  join tj19 on tj18.id = tj19.id
+  join tj20 on tj19.id = tj20.id;
+
+select (trunc(extract(epoch from now())) - :unix_time1) < 100 is_ok;
+
+reset optimizer;
+
 -- Clean up. None of the objects we create are very interesting to keep around.
 reset search_path;
 set client_min_messages='warning';