Clean up cost_sort some more: most callers were double-counting

tglsfdc · tglsfdc · commit 605d84941dec · 1999-05-01T19:47:42.000Z
the cost of reading the source data.
diff --git a/src/backend/optimizer/path/costsize.c b/src/backend/optimizer/path/costsize.c
@@ -7,7 +7,7 @@
  *
  *
  * IDENTIFICATION
- *	  $Header: /cvsroot/pgsql/src/backend/optimizer/path/costsize.c,v 1.35 1999/04/30 04:01:44 tgl Exp $
+ *	  $Header: /cvsroot/pgsql/src/backend/optimizer/path/costsize.c,v 1.36 1999/05/01 19:47:41 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -167,28 +167,23 @@ cost_index(Oid indexid,
 /*
  * cost_sort
  *	  Determines and returns the cost of sorting a relation by considering
- *	  1. the cost of doing an external sort:	XXX this is probably too low
+ *	  the cost of doing an external sort:	XXX this is probably too low
  *				disk = (p lg p)
  *				cpu = *CPU-PAGE-WEIGHT* * (t lg t)
- *	  2. the cost of reading the sort result into memory (another seqscan)
- *		 unless 'noread' is set
  *
  * 'pathkeys' is a list of sort keys
  * 'tuples' is the number of tuples in the relation
  * 'width' is the average tuple width in bytes
- * 'noread' is a flag indicating that the cost of reading the sort
- *				source data should not be included (i.e., the caller
- *				will account for it separately).
  *
  * NOTE: some callers currently pass NULL for pathkeys because they
- * can't conveniently supply sort keys.  Since this routine doesn't
+ * can't conveniently supply the sort keys.  Since this routine doesn't
  * currently do anything with pathkeys anyway, that doesn't matter...
+ * but if it ever does, it should react gracefully to lack of key data.
  *
  * Returns a flonum.
- *
  */
 Cost
-cost_sort(List *pathkeys, int tuples, int width, bool noread)
+cost_sort(List *pathkeys, int tuples, int width)
 {
 	Cost		temp = 0;
 	int			npages = page_size(tuples, width);
@@ -200,6 +195,8 @@ cost_sort(List *pathkeys, int tuples, int width, bool noread)
 	/* We want to be sure the cost of a sort is never estimated as zero,
 	 * even if passed-in tuple count is zero.  Besides, mustn't do log(0)...
 	 */
+	if (tuples <= 0)
+		tuples = 1;
 	if (npages <= 0)
 		npages = 1;
 
@@ -210,13 +207,10 @@ cost_sort(List *pathkeys, int tuples, int width, bool noread)
 	temp += npages * log_npages;
 
 	/*
-	 * could be base_log(pages, NBuffers), but we are only doing 2-way
+	 * could be base_log(tuples, NBuffers), but we are only doing 2-way
 	 * merges
 	 */
-	temp += _cpu_page_wight_ * tuples * log_npages;
-
-	if (!noread)
-		temp += cost_seqscan(_NONAME_RELATION_ID_, npages, tuples);
+	temp += _cpu_page_wight_ * tuples * base_log((double) tuples, 2.0);
 
 	Assert(temp > 0);
 
@@ -282,7 +276,8 @@ cost_nestloop(Cost outercost,
  *	  'outercost' and 'innercost' are the (disk+cpu) costs of scanning the
  *				outer and inner relations
  *	  'outersortkeys' and 'innersortkeys' are lists of the keys to be used
- *				to sort the outer and inner relations
+ *				to sort the outer and inner relations (or NIL if no explicit
+ *				sort is needed because the source path is already ordered)
  *	  'outertuples' and 'innertuples' are the number of tuples in the outer
  *				and inner relations
  *	  'outerwidth' and 'innerwidth' are the (typical) widths (in bytes)
@@ -309,9 +304,9 @@ cost_mergejoin(Cost outercost,
 	temp += outercost;
 	temp += innercost;
 	if (outersortkeys)			/* do we need to sort? */
-		temp += cost_sort(outersortkeys, outersize, outerwidth, true);
+		temp += cost_sort(outersortkeys, outersize, outerwidth);
 	if (innersortkeys)			/* do we need to sort? */
-		temp += cost_sort(innersortkeys, innersize, innerwidth, true);
+		temp += cost_sort(innersortkeys, innersize, innerwidth);
 	temp += _cpu_page_wight_ * (outersize + innersize);
 
 	Assert(temp >= 0);
diff --git a/src/backend/optimizer/path/joinpath.c b/src/backend/optimizer/path/joinpath.c
@@ -7,7 +7,7 @@
  *
  *
  * IDENTIFICATION
- *	  $Header: /cvsroot/pgsql/src/backend/optimizer/path/joinpath.c,v 1.33 1999/04/03 00:18:28 tgl Exp $
+ *	  $Header: /cvsroot/pgsql/src/backend/optimizer/path/joinpath.c,v 1.34 1999/05/01 19:47:42 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -348,7 +348,7 @@ match_unsorted_outer(RelOptInfo *joinrel,
 				(mergeinnerpath->path_cost <
 				 (cheapest_inner->path_cost +
 				  cost_sort(matchedJoinKeys, innerrel->size,
-							innerrel->width, false))));
+							innerrel->width))));
 			if (!path_is_cheaper_than_sort)
 			{
 				varkeys = make_pathkeys_from_joinkeys(matchedJoinKeys,
@@ -464,8 +464,7 @@ match_unsorted_inner(RelOptInfo *joinrel,
 		if (clauses && matchedJoinKeys)
 		{
 			temp1 = outerrel->cheapestpath->path_cost +
-				cost_sort(matchedJoinKeys, outerrel->size, outerrel->width,
-						  false);
+				cost_sort(matchedJoinKeys, outerrel->size, outerrel->width);
 
 			temp2 = (bool) (FLOAT_IS_ZERO(innerpath->outerjoincost)
 							|| (innerpath->outerjoincost > temp1));
diff --git a/src/backend/optimizer/plan/createplan.c b/src/backend/optimizer/plan/createplan.c
@@ -7,7 +7,7 @@
  *
  *
  * IDENTIFICATION
- *	  $Header: /cvsroot/pgsql/src/backend/optimizer/plan/createplan.c,v 1.51 1999/04/30 04:04:27 tgl Exp $
+ *	  $Header: /cvsroot/pgsql/src/backend/optimizer/plan/createplan.c,v 1.52 1999/05/01 19:47:40 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -1106,7 +1106,7 @@ make_sort(List *tlist, Oid nonameid, Plan *lefttree, int keycount)
 	Plan	   *plan = &node->plan;
 
 	copy_costsize(plan, lefttree);
-	plan->cost += cost_sort(NULL, plan->plan_size, plan->plan_width, true);
+	plan->cost += cost_sort(NULL, plan->plan_size, plan->plan_width);
 	plan->state = (EState *) NULL;
 	plan->targetlist = tlist;
 	plan->qual = NIL;
diff --git a/src/include/optimizer/cost.h b/src/include/optimizer/cost.h
@@ -6,7 +6,7 @@
  *
  * Copyright (c) 1994, Regents of the University of California
  *
- * $Id: cost.h,v 1.17 1999/02/13 23:21:43 momjian Exp $
+ * $Id: cost.h,v 1.18 1999/05/01 19:47:39 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -34,7 +34,7 @@ extern Cost cost_seqscan(int relid, int relpages, int reltuples);
 extern Cost cost_index(Oid indexid, int expected_indexpages, Cost selec,
 		   int relpages, int reltuples, int indexpages,
 		   int indextuples, bool is_injoin);
-extern Cost cost_sort(List *pathkeys, int tuples, int width, bool noread);
+extern Cost cost_sort(List *pathkeys, int tuples, int width);
 extern Cost cost_nestloop(Cost outercost, Cost innercost, int outertuples,
 			  int innertuples, int outerpages, bool is_indexjoin);
 extern Cost cost_mergejoin(Cost outercost, Cost innercost,

Original file line number	Diff line number	Diff line change
`@@ -7,7 +7,7 @@`
`7`	`7`	`*`
`8`	`8`	`*`
`9`	`9`	`* IDENTIFICATION`
`10`		`- * $Header: /cvsroot/pgsql/src/backend/optimizer/path/joinpath.c,v 1.33 1999/04/03 00:18:28 tgl Exp $`
	`10`	`+ * $Header: /cvsroot/pgsql/src/backend/optimizer/path/joinpath.c,v 1.34 1999/05/01 19:47:42 tgl Exp $`
`11`	`11`	`*`
`12`	`12`	`*-------------------------------------------------------------------------`
`13`	`13`	`*/`
`@@ -348,7 +348,7 @@ match_unsorted_outer(RelOptInfo *joinrel,`
`348`	`348`	`(mergeinnerpath->path_cost <`
`349`	`349`	`(cheapest_inner->path_cost +`
`350`	`350`	`cost_sort(matchedJoinKeys, innerrel->size,`
`351`		`- innerrel->width, false))));`
	`351`	`+ innerrel->width))));`
`352`	`352`	`if (!path_is_cheaper_than_sort)`
`353`	`353`	`{`
`354`	`354`	`varkeys = make_pathkeys_from_joinkeys(matchedJoinKeys,`
`@@ -464,8 +464,7 @@ match_unsorted_inner(RelOptInfo *joinrel,`
`464`	`464`	`if (clauses && matchedJoinKeys)`
`465`	`465`	`{`
`466`	`466`	`temp1 = outerrel->cheapestpath->path_cost +`
`467`		`- cost_sort(matchedJoinKeys, outerrel->size, outerrel->width,`
`468`		`- false);`
	`467`	`+ cost_sort(matchedJoinKeys, outerrel->size, outerrel->width);`
`469`	`468`
`470`	`469`	`temp2 = (bool) (FLOAT_IS_ZERO(innerpath->outerjoincost)`
`471`	`470`	`\|\| (innerpath->outerjoincost > temp1));`
Original file line number	Diff line number	Diff line change
`@@ -6,7 +6,7 @@`
`6`	`6`	`*`
`7`	`7`	`* Copyright (c) 1994, Regents of the University of California`
`8`	`8`	`*`
`9`		`- * $Id: cost.h,v 1.17 1999/02/13 23:21:43 momjian Exp $`
	`9`	`+ * $Id: cost.h,v 1.18 1999/05/01 19:47:39 tgl Exp $`
`10`	`10`	`*`
`11`	`11`	`*-------------------------------------------------------------------------`
`12`	`12`	`*/`
`@@ -34,7 +34,7 @@ extern Cost cost_seqscan(int relid, int relpages, int reltuples);`
`34`	`34`	`extern Cost cost_index(Oid indexid, int expected_indexpages, Cost selec,`
`35`	`35`	`int relpages, int reltuples, int indexpages,`
`36`	`36`	`int indextuples, bool is_injoin);`
`37`		`-extern Cost cost_sort(List *pathkeys, int tuples, int width, bool noread);`
	`37`	`+extern Cost cost_sort(List *pathkeys, int tuples, int width);`
`38`	`38`	`extern Cost cost_nestloop(Cost outercost, Cost innercost, int outertuples,`
`39`	`39`	`int innertuples, int outerpages, bool is_indexjoin);`
`40`	`40`	`extern Cost cost_mergejoin(Cost outercost, Cost innercost,`