Restructure building of join relation targetlists so that a join plan

node emits only those vars that are actually needed above it in the
plan tree.  (There were comments in the code suggesting that this was
done at some point in the dim past, but for a long time we have just
made join nodes emit everything that either input emitted.)  Aside from
being marginally more efficient, this fixes the problem noted by Peter
Eisentraut where a join above an IN-implemented-as-join might fail,
because the subplan targetlist constructed in the latter case didn't
meet the expectation of including everything.
Along the way, fix some places that were O(N^2) in the targetlist
length.  This is not all the trouble spots for wide queries by any
means, but it's a step forward.

1 files changed, 14 insertions, 6 deletions

diff --git a/src/include/nodes/relation.h b/src/include/nodes/relation.h
index 8392ab505bd..2ab9e0f6e7f 100644
--- a/src/include/nodes/relation.h
+++ b/src/include/nodes/relation.h
@@ -7,7 +7,7 @@
  * Portions Copyright (c) 1996-2002, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
- * $Id: relation.h,v 1.81 2003/06/15 22:51:45 tgl Exp $
+ * $Id: relation.h,v 1.82 2003/06/29 23:05:05 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -89,8 +89,8 @@ typedef struct QualCost
  *			   clauses have been applied (ie, output rows of a plan for it)
  *		width - avg. number of bytes per tuple in the relation after the
  *				appropriate projections have been done (ie, output width)
- *		targetlist - List of TargetEntry nodes for the attributes we need
- *					 to output from this relation
+ *		reltargetlist - List of Var nodes for the attributes we need to
+ *						output from this relation (in no particular order)
  *		pathlist - List of Path nodes, one for each potentially useful
  *				   method of generating the relation
  *		cheapest_startup_path - the pathlist member with lowest startup cost
@@ -107,7 +107,12 @@ typedef struct QualCost
  *		relid - RTE index (this is redundant with the relids field, but
  *				is provided for convenience of access)
  *		rtekind - distinguishes plain relation, subquery, or function RTE
- *		varlist - list of Vars for physical columns (only if table)
+ *		min_attr, max_attr - range of valid AttrNumbers for rel
+ *		attr_needed - array of bitmapsets indicating the highest joinrel
+ *				in which each attribute is needed; if bit 0 is set then
+ *				the attribute is needed as part of final targetlist
+ *		attr_widths - cache space for per-attribute width estimates;
+ *					  zero means not computed yet
  *		indexlist - list of IndexOptInfo nodes for relation's indexes
  *					(always NIL if it's not a table)
  *		pages - number of disk pages in relation (zero if not a table)
@@ -183,7 +188,7 @@ typedef struct RelOptInfo
 	int			width;			/* estimated avg width of result tuples */
 
 	/* materialization information */
-	List	   *targetlist;
+	FastList	reltargetlist;
 	List	   *pathlist;		/* Path structures */
 	struct Path *cheapest_startup_path;
 	struct Path *cheapest_total_path;
@@ -193,7 +198,10 @@ typedef struct RelOptInfo
 	/* information about a base rel (not set for join rels!) */
 	Index		relid;
 	RTEKind		rtekind;		/* RELATION, SUBQUERY, or FUNCTION */
-	List	   *varlist;
+	AttrNumber	min_attr;		/* smallest attrno of rel (often <0) */
+	AttrNumber	max_attr;		/* largest attrno of rel */
+	Relids	   *attr_needed;	/* array indexed [min_attr .. max_attr] */
+	int32	   *attr_widths;	/* array indexed [min_attr .. max_attr] */
 	List	   *indexlist;
 	long		pages;
 	double		tuples;