Major revision of sort-node handling: push knowledge of query

sort order down into planner, instead of handling it only at the very top
level of the planner.  This fixes many things.  An explicit sort is now
avoided if there is a cheaper alternative (typically an indexscan) not
only for ORDER BY, but also for the internal sort of GROUP BY.  It works
even when there is no other reason (such as a WHERE condition) to consider
the indexscan.  It works for indexes on functions.  It works for indexes
on functions, backwards.  It's just so cool...

CAUTION: I have changed the representation of SortClause nodes, therefore
THIS UPDATE BREAKS STORED RULES.  You will need to initdb.

1 files changed, 27 insertions, 8 deletions

diff --git a/src/include/nodes/primnodes.h b/src/include/nodes/primnodes.h
index 2c4d0ffaa72..4eea81446b2 100644
--- a/src/include/nodes/primnodes.h
+++ b/src/include/nodes/primnodes.h
@@ -6,7 +6,7 @@
  *
  * Copyright (c) 1994, Regents of the University of California
  *
- * $Id: primnodes.h,v 1.33 1999/08/16 02:17:39 tgl Exp $
+ * $Id: primnodes.h,v 1.34 1999/08/21 03:49:09 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -25,15 +25,33 @@
 /* ----------------
  * Resdom (Result Domain)
  *		resno			- attribute number
- *		restype			- type of the resdom
- *		restypmod		- type-specific modifier of the result
+ *		restype			- type of the value
+ *		restypmod		- type-specific modifier of the value
  *		resname			- name of the resdom (could be NULL)
+ *		ressortgroupref	- nonzero if referenced by a sort/group clause
  *		reskey			- order of key in a sort (for those > 0)
- *		reskeyop		- sort operator Oid
- *		resgroupref		- set to nonzero if referenced from a group by clause
+ *		reskeyop		- sort operator's regproc Oid
  *		resjunk			- set to true to eliminate the attribute
  *						  from final target list
  *
+ * Notes:
+ * ressortgroupref is the parse/plan-time representation of ORDER BY and
+ * GROUP BY items.  Targetlist entries with ressortgroupref=0 are not
+ * sort/group items.  If ressortgroupref>0, then this item is an ORDER BY or
+ * GROUP BY value.  No two entries in a targetlist may have the same nonzero
+ * ressortgroupref --- but there is no particular meaning to the nonzero
+ * values, except as tags.  (For example, one must not assume that lower
+ * ressortgroupref means a more significant sort key.)  The order of the
+ * associated SortClause or GroupClause lists determine the semantics.
+ *
+ * reskey and reskeyop are the execution-time representation of sorting.
+ * reskey must be zero in any non-sort-key item.  The reskey of sort key
+ * targetlist items for a sort plan node is 1,2,...,n for the n sort keys.
+ * The reskeyop of each such targetlist item is the sort operator's
+ * regproc OID.  reskeyop will be zero in non-sort-key items.
+ *
+ * Both reskey and reskeyop are typically zero during parse/plan stages.
+ * The executor does not pay any attention to ressortgroupref.
  * ----------------
  */
 typedef struct Resdom
@@ -43,9 +61,9 @@ typedef struct Resdom
 	Oid			restype;
 	int32		restypmod;
 	char	   *resname;
+	Index		ressortgroupref;
 	Index		reskey;
 	Oid			reskeyop;
-	Index		resgroupref;
 	bool		resjunk;
 } Resdom;
 
@@ -275,7 +293,8 @@ typedef struct Iter
  *		basetype		- base type Oid of the aggregate
  *		aggtype			- type Oid of final result of the aggregate
  *		target			- attribute or expression we are aggregating on
- *		aggno			- index to ecxt_values
+ *		usenulls		- TRUE to accept null values as inputs
+ *		aggno			- workspace for nodeAgg.c executor
  * ----------------
  */
 typedef struct Aggref
@@ -285,8 +304,8 @@ typedef struct Aggref
 	Oid			basetype;
 	Oid			aggtype;
 	Node	   *target;
-	int			aggno;
 	bool		usenulls;
+	int			aggno;
 } Aggref;
 
 /* ----------------