Make some adjustments to reduce platform dependencies in plan selection.

In particular, there was a mathematical tie between the two possible
nestloop-with-materialized-inner-scan plans for a join (ie, we computed
the same cost with either input on the inside), resulting in a roundoff
error driven choice, if the relations were both small enough to fit in
sort_mem.  Add a small cost factor to ensure we prefer materializing the
smaller input.  This changes several regression test plans, but with any
luck we will now have more stability across platforms.

src/backend/optimizer/path/costsize.c

@@ -49,7 +49,7 @@
  * Portions Copyright (c) 1994, Regents of the University of California
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/optimizer/path/costsize.c,v 1.135 2004/10/23 00:05:27 tgl Exp $
+ *	  $PostgreSQL: pgsql/src/backend/optimizer/path/costsize.c,v 1.136 2004/12/02 01:34:17 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -615,6 +615,15 @@ cost_material(Path *path,
 		run_cost += npages;
 	}
 
+	/*
+	 * Charge a very small amount per inserted tuple, to reflect bookkeeping
+	 * costs.  We use cpu_tuple_cost/10 for this.  This is needed to break
+	 * the tie that would otherwise exist between nestloop with A outer,
+	 * materialized B inner and nestloop with B outer, materialized A inner.
+	 * The extra cost ensures we'll prefer materializing the smaller rel.
+	 */
+	startup_cost += cpu_tuple_cost * 0.1 * tuples;
+
 	/*
 	 * Also charge a small amount per extracted tuple.	We use
 	 * cpu_tuple_cost so that it doesn't appear worthwhile to materialize

src/backend/optimizer/util/plancat.c

@@ -9,7 +9,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/optimizer/util/plancat.c,v 1.98 2004/12/01 19:00:43 tgl Exp $
+ *	  $PostgreSQL: pgsql/src/backend/optimizer/util/plancat.c,v 1.99 2004/12/02 01:34:17 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -268,6 +268,12 @@ estimate_rel_size(Relation rel, int32 *attr_widths,
 				 * but is probably an overestimate for indexes.  Fortunately
 				 * get_relation_info() can clamp the overestimate to the
 				 * parent table's size.
+				 *
+				 * Note: this code intentionally disregards alignment
+				 * considerations, because (a) that would be gilding the
+				 * lily considering how crude the estimate is, and (b)
+				 * it creates platform dependencies in the default plans
+				 * which are kind of a headache for regression testing.
 				 */
 				int32	tuple_width = 0;
 				int		i;
@@ -291,8 +297,7 @@ estimate_rel_size(Relation rel, int32 *attr_widths,
 						attr_widths[i] = item_width;
 					tuple_width += item_width;
 				}
-				tuple_width = MAXALIGN(tuple_width);
-				tuple_width += MAXALIGN(sizeof(HeapTupleHeaderData));
+				tuple_width += sizeof(HeapTupleHeaderData);
 				tuple_width += sizeof(ItemPointerData);
 				/* note: integer division is intentional here */
 				density = (BLCKSZ - sizeof(PageHeaderData)) / tuple_width;

src/test/regress/expected/inherit.out

@@ -557,17 +557,18 @@ insert into bar2 values(2,2,2);
 insert into bar2 values(3,3,3);
 insert into bar2 values(4,4,4);
 update bar set f2 = f2 + 100 where f1 in (select f1 from foo);
-SELECT relname, bar.* FROM bar, pg_class where bar.tableoid = pg_class.oid;
+SELECT relname, bar.* FROM bar, pg_class where bar.tableoid = pg_class.oid
+order by 1,2;
  relname | f1 | f2  
 ---------+----+-----
- bar     |  4 |   4
- bar     |  3 | 103
- bar     |  2 | 102
  bar     |  1 | 101
- bar2    |  4 |   4
- bar2    |  3 | 103
- bar2    |  2 | 102
+ bar     |  2 | 102
+ bar     |  3 | 103
+ bar     |  4 |   4
  bar2    |  1 | 101
+ bar2    |  2 | 102
+ bar2    |  3 | 103
+ bar2    |  4 |   4
 (8 rows)
 
 /* Test inheritance of structure (LIKE) */

src/test/regress/sql/inherit.sql

@@ -118,7 +118,8 @@ insert into bar2 values(4,4,4);
 
 update bar set f2 = f2 + 100 where f1 in (select f1 from foo);
 
-SELECT relname, bar.* FROM bar, pg_class where bar.tableoid = pg_class.oid;
+SELECT relname, bar.* FROM bar, pg_class where bar.tableoid = pg_class.oid
+order by 1,2;
 
 
 /* Test inheritance of structure (LIKE) */

src/test/regress/sql/join.sql

@@ -167,11 +167,11 @@ SELECT '' AS "xxx", *
 
 SELECT '' AS "xxx", *
   FROM J1_TBL LEFT OUTER JOIN J2_TBL USING (i)
-  ORDER BY i;
+  ORDER BY i, k;
 
 SELECT '' AS "xxx", *
   FROM J1_TBL LEFT JOIN J2_TBL USING (i)
-  ORDER BY i;
+  ORDER BY i, k;
 
 SELECT '' AS "xxx", *
   FROM J1_TBL RIGHT OUTER JOIN J2_TBL USING (i);
@@ -181,11 +181,11 @@ SELECT '' AS "xxx", *
 
 SELECT '' AS "xxx", *
   FROM J1_TBL FULL OUTER JOIN J2_TBL USING (i)
-  ORDER BY i, t;
+  ORDER BY i, k;
 
 SELECT '' AS "xxx", *
   FROM J1_TBL FULL JOIN J2_TBL USING (i)
-  ORDER BY i, t;
+  ORDER BY i, k;
 
 SELECT '' AS "xxx", *
   FROM J1_TBL LEFT JOIN J2_TBL USING (i) WHERE (k = 1);