Fix thinko in new logic about pushing down non-nullability constraints:

constraints appearing in outer-join qualification clauses are restricted
as to when and where they can be pushed down.  Add regression test
to catch future errors in this area.

src/backend/optimizer/prep/prepjointree.c

@@ -16,7 +16,7 @@
  *
  *
  * IDENTIFICATION
- *	  $Header: /cvsroot/pgsql/src/backend/optimizer/prep/prepjointree.c,v 1.5 2003/02/09 23:57:19 tgl Exp $
+ *	  $Header: /cvsroot/pgsql/src/backend/optimizer/prep/prepjointree.c,v 1.6 2003/02/10 17:08:50 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -694,23 +694,45 @@ reduce_outer_joins_pass2(Node *jtnode,
 		/* Only recurse if there's more to do below here */
 		if (left_state->contains_outer || right_state->contains_outer)
 		{
+			Relids		local_nonnullable;
 			Relids		pass_nonnullable;
 
 			/*
-			 * Scan join quals to see if we can add any nonnullability
-			 * constraints.  (Okay to do this even if join is still outer.)
+			 * If this join is (now) inner, we can add any nonnullability
+			 * constraints its quals provide to those we got from above.
+			 * But if it is outer, we can only pass down the local constraints
+			 * into the nullable side, because an outer join never eliminates
+			 * any rows from its non-nullable side.  If it's a FULL join then
+			 * it doesn't eliminate anything from either side.
 			 */
-			pass_nonnullable = find_nonnullable_rels(j->quals, true);
-			pass_nonnullable = bms_add_members(pass_nonnullable,
+			if (jointype != JOIN_FULL)
+			{
+				local_nonnullable = find_nonnullable_rels(j->quals, true);
+				local_nonnullable = bms_add_members(local_nonnullable,
 													nonnullable_rels);
-			/* And recurse as needed */
+			}
+			else
+				local_nonnullable = NULL; /* no use in calculating it */
+
 			if (left_state->contains_outer)
+			{
+				if (jointype == JOIN_INNER || jointype == JOIN_RIGHT)
+					pass_nonnullable = local_nonnullable;
+				else
+					pass_nonnullable = nonnullable_rels;
 				reduce_outer_joins_pass2(j->larg, left_state, parse,
 										 pass_nonnullable);
+			}
 			if (right_state->contains_outer)
+			{
+				if (jointype == JOIN_INNER || jointype == JOIN_LEFT)
+					pass_nonnullable = local_nonnullable;
+				else
+					pass_nonnullable = nonnullable_rels;
 				reduce_outer_joins_pass2(j->rarg, right_state, parse,
 										 pass_nonnullable);
-			bms_free(pass_nonnullable);
+			}
+			bms_free(local_nonnullable);
 		}
 	}
 	else

src/test/regress/expected/join.out

@@ -2004,6 +2004,129 @@ NATURAL FULL JOIN
  dd   |      |   42 |    2 |     
 (4 rows)
 
+-- Test for propagation of nullability constraints into sub-joins
+create temp table x (x1 int, x2 int);
+insert into x values (1,11);
+insert into x values (2,22);
+insert into x values (3,null);
+insert into x values (4,44);
+insert into x values (5,null);
+create temp table y (y1 int, y2 int);
+insert into y values (1,111);
+insert into y values (2,222);
+insert into y values (3,333);
+insert into y values (4,null);
+select * from x;
+ x1 | x2 
+----+----
+  1 | 11
+  2 | 22
+  3 |   
+  4 | 44
+  5 |   
+(5 rows)
+
+select * from y;
+ y1 | y2  
+----+-----
+  1 | 111
+  2 | 222
+  3 | 333
+  4 |    
+(4 rows)
+
+select * from x left join y on (x1 = y1 and x2 is not null);
+ x1 | x2 | y1 | y2  
+----+----+----+-----
+  1 | 11 |  1 | 111
+  2 | 22 |  2 | 222
+  3 |    |    |    
+  4 | 44 |  4 |    
+  5 |    |    |    
+(5 rows)
+
+select * from x left join y on (x1 = y1 and y2 is not null);
+ x1 | x2 | y1 | y2  
+----+----+----+-----
+  1 | 11 |  1 | 111
+  2 | 22 |  2 | 222
+  3 |    |  3 | 333
+  4 | 44 |    |    
+  5 |    |    |    
+(5 rows)
+
+select * from (x left join y on (x1 = y1)) left join x xx(xx1,xx2)
+on (x1 = xx1);
+ x1 | x2 | y1 | y2  | xx1 | xx2 
+----+----+----+-----+-----+-----
+  1 | 11 |  1 | 111 |   1 |  11
+  2 | 22 |  2 | 222 |   2 |  22
+  3 |    |  3 | 333 |   3 |    
+  4 | 44 |  4 |     |   4 |  44
+  5 |    |    |     |   5 |    
+(5 rows)
+
+select * from (x left join y on (x1 = y1)) left join x xx(xx1,xx2)
+on (x1 = xx1 and x2 is not null);
+ x1 | x2 | y1 | y2  | xx1 | xx2 
+----+----+----+-----+-----+-----
+  1 | 11 |  1 | 111 |   1 |  11
+  2 | 22 |  2 | 222 |   2 |  22
+  3 |    |  3 | 333 |     |    
+  4 | 44 |  4 |     |   4 |  44
+  5 |    |    |     |     |    
+(5 rows)
+
+select * from (x left join y on (x1 = y1)) left join x xx(xx1,xx2)
+on (x1 = xx1 and y2 is not null);
+ x1 | x2 | y1 | y2  | xx1 | xx2 
+----+----+----+-----+-----+-----
+  1 | 11 |  1 | 111 |   1 |  11
+  2 | 22 |  2 | 222 |   2 |  22
+  3 |    |  3 | 333 |   3 |    
+  4 | 44 |  4 |     |     |    
+  5 |    |    |     |     |    
+(5 rows)
+
+select * from (x left join y on (x1 = y1)) left join x xx(xx1,xx2)
+on (x1 = xx1 and xx2 is not null);
+ x1 | x2 | y1 | y2  | xx1 | xx2 
+----+----+----+-----+-----+-----
+  1 | 11 |  1 | 111 |   1 |  11
+  2 | 22 |  2 | 222 |   2 |  22
+  3 |    |  3 | 333 |     |    
+  4 | 44 |  4 |     |   4 |  44
+  5 |    |    |     |     |    
+(5 rows)
+
+-- these should NOT give the same answers as above
+select * from (x left join y on (x1 = y1)) left join x xx(xx1,xx2)
+on (x1 = xx1) where (x2 is not null);
+ x1 | x2 | y1 | y2  | xx1 | xx2 
+----+----+----+-----+-----+-----
+  1 | 11 |  1 | 111 |   1 |  11
+  2 | 22 |  2 | 222 |   2 |  22
+  4 | 44 |  4 |     |   4 |  44
+(3 rows)
+
+select * from (x left join y on (x1 = y1)) left join x xx(xx1,xx2)
+on (x1 = xx1) where (y2 is not null);
+ x1 | x2 | y1 | y2  | xx1 | xx2 
+----+----+----+-----+-----+-----
+  1 | 11 |  1 | 111 |   1 |  11
+  2 | 22 |  2 | 222 |   2 |  22
+  3 |    |  3 | 333 |   3 |    
+(3 rows)
+
+select * from (x left join y on (x1 = y1)) left join x xx(xx1,xx2)
+on (x1 = xx1) where (xx2 is not null);
+ x1 | x2 | y1 | y2  | xx1 | xx2 
+----+----+----+-----+-----+-----
+  1 | 11 |  1 | 111 |   1 |  11
+  2 | 22 |  2 | 222 |   2 |  22
+  4 | 44 |  4 |     |   4 |  44
+(3 rows)
+
 --
 -- Clean up
 --

src/test/regress/sql/join.sql

@@ -292,6 +292,45 @@ NATURAL FULL JOIN
     (SELECT name, n as s3_n FROM t3) as s3
   ) ss2;
 
+
+-- Test for propagation of nullability constraints into sub-joins
+
+create temp table x (x1 int, x2 int);
+insert into x values (1,11);
+insert into x values (2,22);
+insert into x values (3,null);
+insert into x values (4,44);
+insert into x values (5,null);
+
+create temp table y (y1 int, y2 int);
+insert into y values (1,111);
+insert into y values (2,222);
+insert into y values (3,333);
+insert into y values (4,null);
+
+select * from x;
+select * from y;
+
+select * from x left join y on (x1 = y1 and x2 is not null);
+select * from x left join y on (x1 = y1 and y2 is not null);
+
+select * from (x left join y on (x1 = y1)) left join x xx(xx1,xx2)
+on (x1 = xx1);
+select * from (x left join y on (x1 = y1)) left join x xx(xx1,xx2)
+on (x1 = xx1 and x2 is not null);
+select * from (x left join y on (x1 = y1)) left join x xx(xx1,xx2)
+on (x1 = xx1 and y2 is not null);
+select * from (x left join y on (x1 = y1)) left join x xx(xx1,xx2)
+on (x1 = xx1 and xx2 is not null);
+-- these should NOT give the same answers as above
+select * from (x left join y on (x1 = y1)) left join x xx(xx1,xx2)
+on (x1 = xx1) where (x2 is not null);
+select * from (x left join y on (x1 = y1)) left join x xx(xx1,xx2)
+on (x1 = xx1) where (y2 is not null);
+select * from (x left join y on (x1 = y1)) left join x xx(xx1,xx2)
+on (x1 = xx1) where (xx2 is not null);
+
+
 --
 -- Clean up
 --