New cost model for planning, incorporating a penalty for random page

accesses versus sequential accesses, a (very crude) estimate of the
effects of caching on random page accesses, and cost to evaluate WHERE-
clause expressions.  Export critical parameters for this model as SET
variables.  Also, create SET variables for the planner's enable flags
(enable_seqscan, enable_indexscan, etc) so that these can be controlled
more conveniently than via PGOPTIONS.

Planner now estimates both startup cost (cost before retrieving
first tuple) and total cost of each path, so it can optimize queries
with LIMIT on a reasonable basis by interpolating between these costs.
Same facility is a win for EXISTS(...) subqueries and some other cases.

Redesign pathkey representation to achieve a major speedup in planning
(I saw as much as 5X on a 10-way join); also minor changes in planner
to reduce memory consumption by recycling discarded Path nodes and
not constructing unnecessary lists.

Minor cleanups to display more-plausible costs in some cases in
EXPLAIN output.

Initdb forced by change in interface to index cost estimation
functions.

1 files changed, 55 insertions, 65 deletions

diff --git a/src/backend/nodes/readfuncs.c b/src/backend/nodes/readfuncs.c
index 7d56b603b85..7d1e0b4cccf 100644
--- a/src/backend/nodes/readfuncs.c
+++ b/src/backend/nodes/readfuncs.c
@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $Header: /cvsroot/pgsql/src/backend/nodes/readfuncs.c,v 1.83 2000/02/15 03:37:09 thomas Exp $
+ *	  $Header: /cvsroot/pgsql/src/backend/nodes/readfuncs.c,v 1.84 2000/02/15 20:49:12 tgl Exp $
  *
  * NOTES
  *	  Most of the read functions for plan nodes are tested. (In fact, they
@@ -217,9 +217,13 @@ _getPlan(Plan *node)
 	char	   *token;
 	int			length;
 
-	token = lsptok(NULL, &length);		/* first token is :cost */
+	token = lsptok(NULL, &length);		/* first token is :startup_cost */
 	token = lsptok(NULL, &length);		/* next is the actual cost */
-	node->cost = (Cost) atof(token);
+	node->startup_cost = (Cost) atof(token);
+
+	token = lsptok(NULL, &length);		/* skip the :total_cost */
+	token = lsptok(NULL, &length);		/* next is the actual cost */
+	node->total_cost = (Cost) atof(token);
 
 	token = lsptok(NULL, &length);		/* skip the :rows */
 	token = lsptok(NULL, &length);		/* get the plan_rows */
@@ -520,7 +524,6 @@ _readIndexScan()
 
 	token = lsptok(NULL, &length);		/* eat :indxorderdir */
 	token = lsptok(NULL, &length);		/* get indxorderdir */
-
 	local_node->indxorderdir = atoi(token);
 
 	return local_node;
@@ -1275,18 +1278,15 @@ _readRelOptInfo()
 	token = lsptok(NULL, &length);		/* get :pathlist */
 	local_node->pathlist = nodeRead(true);		/* now read it */
 
-	/*
-	 * Not sure if these are nodes or not.	They're declared as struct
-	 * Path *.	Since i don't know, i'll just print the addresses for now.
-	 * This can be changed later, if necessary.
-	 */
-
-	token = lsptok(NULL, &length);		/* get :cheapestpath */
-	token = lsptok(NULL, &length);		/* get @ */
-	token = lsptok(NULL, &length);		/* now read it */
+	token = lsptok(NULL, &length);		/* get :cheapest_startup_path */
+	local_node->cheapest_startup_path = nodeRead(true);		/* now read it */
 
-	sscanf(token, "%x", (unsigned int *) &local_node->cheapestpath);
+	token = lsptok(NULL, &length);		/* get :cheapest_total_path */
+	local_node->cheapest_total_path = nodeRead(true);		/* now read it */
 
+	token = lsptok(NULL, &length);		/* eat :pruneable */
+	token = lsptok(NULL, &length);		/* get :pruneable */
+	local_node->pruneable = (token[0] == 't') ? true : false;
 
 	token = lsptok(NULL, &length);		/* get :baserestrictinfo */
 	local_node->baserestrictinfo = nodeRead(true);	/* now read it */
@@ -1322,29 +1322,6 @@ _readTargetEntry()
 	return local_node;
 }
 
-static List *
-_readList()
-{
-	List	   *local_node = NULL;
-	char	   *token;
-	int			length;
-
-	token = lsptok(NULL, &length);		/* eat "(" */
-	token = lsptok(NULL, &length);		/* get "{" */
-	while (strncmp(token, "{", length) == 0)
-	{
-		nconc(local_node, nodeRead(true));
-
-		token = lsptok(NULL, &length);		/* eat ")" */
-		if (strncmp(token, "}", length) != 0)
-			elog(ERROR, "badly formatted attribute list"
-				 " in planstring \"%.10s\"...\n", token);
-		token = lsptok(NULL, &length);		/* "{" or ")" */
-	}
-
-	return local_node;
-}
-
 static Attr *
 _readAttr()
 {
@@ -1356,13 +1333,10 @@ _readAttr()
 
 	token = lsptok(NULL, &length);		/* eat :relname */
 	token = lsptok(NULL, &length);		/* get relname */
-	if (length == 0)
-		local_node->relname = pstrdup("");
-	else
-		local_node->relname = debackslash(token, length);
+	local_node->relname = debackslash(token, length);
 
 	token = lsptok(NULL, &length);		/* eat :attrs */
-	local_node->attrs = _readList();
+	local_node->attrs = nodeRead(true);	/* now read it */
 
 	return local_node;
 }
@@ -1388,7 +1362,7 @@ _readRangeTblEntry()
 		local_node->relname = debackslash(token, length);
 
 	token = lsptok(NULL, &length);		/* eat :ref */
-	local_node->ref = nodeRead(true);
+	local_node->ref = nodeRead(true);	/* now read it */
 
 	token = lsptok(NULL, &length);		/* eat :relid */
 	token = lsptok(NULL, &length);		/* get :relid */
@@ -1450,9 +1424,13 @@ _readPath()
 	token = lsptok(NULL, &length);		/* now read it */
 	local_node->pathtype = atol(token);
 
-	token = lsptok(NULL, &length);		/* get :cost */
+	token = lsptok(NULL, &length);		/* get :startup_cost */
+	token = lsptok(NULL, &length);		/* now read it */
+	local_node->startup_cost = (Cost) atof(token);
+
+	token = lsptok(NULL, &length);		/* get :total_cost */
 	token = lsptok(NULL, &length);		/* now read it */
-	local_node->path_cost = (Cost) atof(token);
+	local_node->total_cost = (Cost) atof(token);
 
 	token = lsptok(NULL, &length);		/* get :pathkeys */
 	local_node->pathkeys = nodeRead(true);		/* now read it */
@@ -1479,9 +1457,13 @@ _readIndexPath()
 	token = lsptok(NULL, &length);		/* now read it */
 	local_node->path.pathtype = atol(token);
 
-	token = lsptok(NULL, &length);		/* get :cost */
+	token = lsptok(NULL, &length);		/* get :startup_cost */
 	token = lsptok(NULL, &length);		/* now read it */
-	local_node->path.path_cost = (Cost) atof(token);
+	local_node->path.startup_cost = (Cost) atof(token);
+
+	token = lsptok(NULL, &length);		/* get :total_cost */
+	token = lsptok(NULL, &length);		/* now read it */
+	local_node->path.total_cost = (Cost) atof(token);
 
 	token = lsptok(NULL, &length);		/* get :pathkeys */
 	local_node->path.pathkeys = nodeRead(true); /* now read it */
@@ -1492,6 +1474,10 @@ _readIndexPath()
 	token = lsptok(NULL, &length);		/* get :indexqual */
 	local_node->indexqual = nodeRead(true);		/* now read it */
 
+	token = lsptok(NULL, &length);		/* get :indexscandir */
+	token = lsptok(NULL, &length);		/* now read it */
+	local_node->indexscandir = (ScanDirection) atoi(token);
+
 	token = lsptok(NULL, &length);		/* get :joinrelids */
 	local_node->joinrelids = toIntList(nodeRead(true));
 
@@ -1517,9 +1503,13 @@ _readTidPath()
 	token = lsptok(NULL, &length);		/* now read it */
 	local_node->path.pathtype = atol(token);
 
-	token = lsptok(NULL, &length);		/* get :cost */
+	token = lsptok(NULL, &length);		/* get :startup_cost */
 	token = lsptok(NULL, &length);		/* now read it */
-	local_node->path.path_cost = (Cost) atof(token);
+	local_node->path.startup_cost = (Cost) atof(token);
+
+	token = lsptok(NULL, &length);		/* get :total_cost */
+	token = lsptok(NULL, &length);		/* now read it */
+	local_node->path.total_cost = (Cost) atof(token);
 
 	token = lsptok(NULL, &length);		/* get :pathkeys */
 	local_node->path.pathkeys = nodeRead(true); /* now read it */
@@ -1552,9 +1542,13 @@ _readNestPath()
 	token = lsptok(NULL, &length);		/* now read it */
 	local_node->path.pathtype = atol(token);
 
-	token = lsptok(NULL, &length);		/* get :cost */
+	token = lsptok(NULL, &length);		/* get :startup_cost */
+	token = lsptok(NULL, &length);		/* now read it */
+	local_node->path.startup_cost = (Cost) atof(token);
+
+	token = lsptok(NULL, &length);		/* get :total_cost */
 	token = lsptok(NULL, &length);		/* now read it */
-	local_node->path.path_cost = (Cost) atof(token);
+	local_node->path.total_cost = (Cost) atof(token);
 
 	token = lsptok(NULL, &length);		/* get :pathkeys */
 	local_node->path.pathkeys = nodeRead(true); /* now read it */
@@ -1588,13 +1582,15 @@ _readMergePath()
 
 	token = lsptok(NULL, &length);		/* get :pathtype */
 	token = lsptok(NULL, &length);		/* now read it */
-
 	local_node->jpath.path.pathtype = atol(token);
 
-	token = lsptok(NULL, &length);		/* get :cost */
+	token = lsptok(NULL, &length);		/* get :startup_cost */
 	token = lsptok(NULL, &length);		/* now read it */
+	local_node->jpath.path.startup_cost = (Cost) atof(token);
 
-	local_node->jpath.path.path_cost = (Cost) atof(token);
+	token = lsptok(NULL, &length);		/* get :total_cost */
+	token = lsptok(NULL, &length);		/* now read it */
+	local_node->jpath.path.total_cost = (Cost) atof(token);
 
 	token = lsptok(NULL, &length);		/* get :pathkeys */
 	local_node->jpath.path.pathkeys = nodeRead(true);	/* now read it */
@@ -1637,13 +1633,15 @@ _readHashPath()
 
 	token = lsptok(NULL, &length);		/* get :pathtype */
 	token = lsptok(NULL, &length);		/* now read it */
-
 	local_node->jpath.path.pathtype = atol(token);
 
-	token = lsptok(NULL, &length);		/* get :cost */
+	token = lsptok(NULL, &length);		/* get :startup_cost */
 	token = lsptok(NULL, &length);		/* now read it */
+	local_node->jpath.path.startup_cost = (Cost) atof(token);
 
-	local_node->jpath.path.path_cost = (Cost) atof(token);
+	token = lsptok(NULL, &length);		/* get :total_cost */
+	token = lsptok(NULL, &length);		/* now read it */
+	local_node->jpath.path.total_cost = (Cost) atof(token);
 
 	token = lsptok(NULL, &length);		/* get :pathkeys */
 	local_node->jpath.path.pathkeys = nodeRead(true);	/* now read it */
@@ -1886,14 +1884,6 @@ parsePlanString(void)
 		return_value = _readCaseWhen();
 	else if (length == 7 && strncmp(token, "ROWMARK", length) == 0)
 		return_value = _readRowMark();
-#if 0
-	else if (length == 1 && strncmp(token, "{", length) == 0)
-	{
-		/* raw list (of strings?) found in Attr structure - thomas 2000-02-09 */
-		return_value = nodeRead(true);
-		token = lsptok(NULL, &length);	/* eat trailing brace */
-	}
-#endif
 	else
 		elog(ERROR, "badly formatted planstring \"%.10s\"...\n", token);