Change hash index creation so that rather than always establishing exactly

two buckets at the start, we create a number of buckets appropriate for the
estimated size of the table.  This avoids a lot of expensive bucket-split
actions during initial index build on an already-populated table.

This is one of the two core ideas of Tom Raney and Shreya Bhargava's patch
to reduce hash index build time.  I'm committing it separately to make it
easier for people to test the effects of this separately from the effects
of their other core idea (pre-sorting the index entries by bucket number).

src/backend/optimizer/util/plancat.c

@@ -9,7 +9,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/optimizer/util/plancat.c,v 1.140 2008/01/12 00:11:39 tgl Exp $
+ *	  $PostgreSQL: pgsql/src/backend/optimizer/util/plancat.c,v 1.141 2008/03/15 20:46:31 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -45,8 +45,6 @@ bool		constraint_exclusion = false;
 get_relation_info_hook_type get_relation_info_hook = NULL;
 
 
-static void estimate_rel_size(Relation rel, int32 *attr_widths,
-				  BlockNumber *pages, double *tuples);
 static List *get_relation_constraints(Oid relationObjectId, RelOptInfo *rel,
 						 bool include_notnull);
 
@@ -319,7 +317,7 @@ get_relation_info(PlannerInfo *root, Oid relationObjectId, bool inhparent,
  * relation's attr_width[] cache; we fill this in if we have need to compute
  * the attribute widths for estimation purposes.
  */
-static void
+void
 estimate_rel_size(Relation rel, int32 *attr_widths,
 				  BlockNumber *pages, double *tuples)
 {