Get rid of adjust_appendrel_attr_needed(), which has been broken ever since

we extended the appendrel mechanism to support UNION ALL optimization.  The
reason nobody noticed was that we are not actually using attr_needed data for
appendrel children; hence it seems more reasonable to rip it out than fix it.
Back-patch to 8.2 because an Assert failure is possible in corner cases.
Per examination of an example from Jim Nasby.

In HEAD, also get rid of AppendRelInfo.col_mappings, which is quite inadequate
to represent UNION ALL situations; depend entirely on translated_vars instead.

src/backend/nodes/copyfuncs.c

@@ -15,7 +15,7 @@
  * Portions Copyright (c) 1994, Regents of the University of California
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/nodes/copyfuncs.c,v 1.410 2008/10/31 08:39:20 heikki Exp $
+ *	  $PostgreSQL: pgsql/src/backend/nodes/copyfuncs.c,v 1.411 2008/11/11 18:13:32 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -1640,7 +1640,6 @@ _copyAppendRelInfo(AppendRelInfo *from)
 	COPY_SCALAR_FIELD(child_relid);
 	COPY_SCALAR_FIELD(parent_reltype);
 	COPY_SCALAR_FIELD(child_reltype);
-	COPY_NODE_FIELD(col_mappings);
 	COPY_NODE_FIELD(translated_vars);
 	COPY_SCALAR_FIELD(parent_reloid);
 

src/backend/nodes/equalfuncs.c

@@ -22,7 +22,7 @@
  * Portions Copyright (c) 1994, Regents of the University of California
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/nodes/equalfuncs.c,v 1.335 2008/10/31 08:39:20 heikki Exp $
+ *	  $PostgreSQL: pgsql/src/backend/nodes/equalfuncs.c,v 1.336 2008/11/11 18:13:32 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -806,7 +806,6 @@ _equalAppendRelInfo(AppendRelInfo *a, AppendRelInfo *b)
 	COMPARE_SCALAR_FIELD(child_relid);
 	COMPARE_SCALAR_FIELD(parent_reltype);
 	COMPARE_SCALAR_FIELD(child_reltype);
-	COMPARE_NODE_FIELD(col_mappings);
 	COMPARE_NODE_FIELD(translated_vars);
 	COMPARE_SCALAR_FIELD(parent_reloid);
 

src/backend/nodes/outfuncs.c

@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/nodes/outfuncs.c,v 1.343 2008/10/21 20:42:52 tgl Exp $
+ *	  $PostgreSQL: pgsql/src/backend/nodes/outfuncs.c,v 1.344 2008/11/11 18:13:32 tgl Exp $
  *
  * NOTES
  *	  Every node type that can appear in stored rules' parsetrees *must*
@@ -1628,7 +1628,6 @@ _outAppendRelInfo(StringInfo str, AppendRelInfo *node)
 	WRITE_UINT_FIELD(child_relid);
 	WRITE_OID_FIELD(parent_reltype);
 	WRITE_OID_FIELD(child_reltype);
-	WRITE_NODE_FIELD(col_mappings);
 	WRITE_NODE_FIELD(translated_vars);
 	WRITE_OID_FIELD(parent_reloid);
 }

src/backend/optimizer/path/allpaths.c

@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/optimizer/path/allpaths.c,v 1.175 2008/10/21 20:42:52 tgl Exp $
+ *	  $PostgreSQL: pgsql/src/backend/optimizer/path/allpaths.c,v 1.176 2008/11/11 18:13:32 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -382,14 +382,12 @@ set_append_rel_pathlist(PlannerInfo *root, RelOptInfo *rel,
 		}
 
 		/*
-		 * Copy the parent's attr_needed data as well, with appropriate
-		 * adjustment of relids and attribute numbers.
+		 * Note: we could compute appropriate attr_needed data for the
+		 * child's variables, by transforming the parent's attr_needed
+		 * through the translated_vars mapping.  However, currently there's
+		 * no need because attr_needed is only examined for base relations
+		 * not otherrels.  So we just leave the child's attr_needed empty.
 		 */
-		pfree(childrel->attr_needed);
-		childrel->attr_needed =
-			adjust_appendrel_attr_needed(rel, appinfo,
-										 childrel->min_attr,
-										 childrel->max_attr);
 
 		/*
 		 * Compute the child's access paths, and add the cheapest one to the

src/backend/optimizer/prep/prepjointree.c

@@ -16,7 +16,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/optimizer/prep/prepjointree.c,v 1.58 2008/10/22 20:17:52 tgl Exp $
+ *	  $PostgreSQL: pgsql/src/backend/optimizer/prep/prepjointree.c,v 1.59 2008/11/11 18:13:32 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -54,9 +54,8 @@ static Node *pull_up_simple_union_all(PlannerInfo *root, Node *jtnode,
 static void pull_up_union_leaf_queries(Node *setOp, PlannerInfo *root,
 						  int parentRTindex, Query *setOpQuery,
 						  int childRToffset);
-static void make_setop_translation_lists(Query *query,
-							 Index newvarno,
-							 List **col_mappings, List **translated_vars);
+static void make_setop_translation_list(Query *query, Index newvarno,
+							 List **translated_vars);
 static bool is_simple_subquery(Query *subquery);
 static bool is_simple_union_all(Query *subquery);
 static bool is_simple_union_all_recurse(Node *setOp, Query *setOpQuery,
@@ -839,9 +838,8 @@ pull_up_union_leaf_queries(Node *setOp, PlannerInfo *root, int parentRTindex,
 		appinfo->child_relid = childRTindex;
 		appinfo->parent_reltype = InvalidOid;
 		appinfo->child_reltype = InvalidOid;
-		make_setop_translation_lists(setOpQuery, childRTindex,
-									 &appinfo->col_mappings,
-									 &appinfo->translated_vars);
+		make_setop_translation_list(setOpQuery, childRTindex,
+									&appinfo->translated_vars);
 		appinfo->parent_reloid = InvalidOid;
 		root->append_rel_list = lappend(root->append_rel_list, appinfo);
 
@@ -874,17 +872,16 @@ pull_up_union_leaf_queries(Node *setOp, PlannerInfo *root, int parentRTindex,
 }
 
 /*
- * make_setop_translation_lists
- *	  Build the lists of translations from parent Vars to child Vars for
- *	  a UNION ALL member.  We need both a column number mapping list
- *	  and a list of Vars representing the child columns.
+ * make_setop_translation_list
+ *	  Build the list of translations from parent Vars to child Vars for
+ *	  a UNION ALL member.  (At this point it's just a simple list of
+ *	  referencing Vars, but if we succeed in pulling up the member
+ *	  subquery, the Vars will get replaced by pulled-up expressions.)
  */
 static void
-make_setop_translation_lists(Query *query,
-							 Index newvarno,
-							 List **col_mappings, List **translated_vars)
+make_setop_translation_list(Query *query, Index newvarno,
+							List **translated_vars)
 {
-	List	   *numbers = NIL;
 	List	   *vars = NIL;
 	ListCell   *l;
 
@@ -895,7 +892,6 @@ make_setop_translation_lists(Query *query,
 		if (tle->resjunk)
 			continue;
 
-		numbers = lappend_int(numbers, tle->resno);
 		vars = lappend(vars, makeVar(newvarno,
 									 tle->resno,
 									 exprType((Node *) tle->expr),
@@ -903,7 +899,6 @@ make_setop_translation_lists(Query *query,
 									 0));
 	}
 
-	*col_mappings = numbers;
 	*translated_vars = vars;
 }
 

src/backend/optimizer/prep/prepunion.c

@@ -22,7 +22,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/optimizer/prep/prepunion.c,v 1.160 2008/10/22 20:17:52 tgl Exp $
+ *	  $PostgreSQL: pgsql/src/backend/optimizer/prep/prepunion.c,v 1.161 2008/11/11 18:13:32 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -91,11 +91,10 @@ static List *generate_append_tlist(List *colTypes, bool flag,
 static List *generate_setop_grouplist(SetOperationStmt *op, List *targetlist);
 static void expand_inherited_rtentry(PlannerInfo *root, RangeTblEntry *rte,
 						 Index rti);
-static void make_inh_translation_lists(Relation oldrelation,
-						   Relation newrelation,
-						   Index newvarno,
-						   List **col_mappings,
-						   List **translated_vars);
+static void make_inh_translation_list(Relation oldrelation,
+						  Relation newrelation,
+						  Index newvarno,
+						  List **translated_vars);
 static Node *adjust_appendrel_attrs_mutator(Node *node,
 							   AppendRelInfo *context);
 static Relids adjust_relid_set(Relids relids, Index oldrelid, Index newrelid);
@@ -1279,9 +1278,8 @@ expand_inherited_rtentry(PlannerInfo *root, RangeTblEntry *rte, Index rti)
 		appinfo->child_relid = childRTindex;
 		appinfo->parent_reltype = oldrelation->rd_rel->reltype;
 		appinfo->child_reltype = newrelation->rd_rel->reltype;
-		make_inh_translation_lists(oldrelation, newrelation, childRTindex,
-								   &appinfo->col_mappings,
-								   &appinfo->translated_vars);
+		make_inh_translation_list(oldrelation, newrelation, childRTindex,
+								  &appinfo->translated_vars);
 		appinfo->parent_reloid = parentOID;
 		appinfos = lappend(appinfos, appinfo);
 
@@ -1316,19 +1314,17 @@ expand_inherited_rtentry(PlannerInfo *root, RangeTblEntry *rte, Index rti)
 }
 
 /*
- * make_inh_translation_lists
- *	  Build the lists of translations from parent Vars to child Vars for
- *	  an inheritance child.  We need both a column number mapping list
- *	  and a list of Vars representing the child columns.
+ * make_inh_translation_list
+ *	  Build the list of translations from parent Vars to child Vars for
+ *	  an inheritance child.
  *
  * For paranoia's sake, we match type as well as attribute name.
  */
 static void
-make_inh_translation_lists(Relation oldrelation, Relation newrelation,
-						   Index newvarno,
-						   List **col_mappings, List **translated_vars)
+make_inh_translation_list(Relation oldrelation, Relation newrelation,
+						  Index newvarno,
+						  List **translated_vars)
 {
-	List	   *numbers = NIL;
 	List	   *vars = NIL;
 	TupleDesc	old_tupdesc = RelationGetDescr(oldrelation);
 	TupleDesc	new_tupdesc = RelationGetDescr(newrelation);
@@ -1347,8 +1343,7 @@ make_inh_translation_lists(Relation oldrelation, Relation newrelation,
 		att = old_tupdesc->attrs[old_attno];
 		if (att->attisdropped)
 		{
-			/* Just put 0/NULL into this list entry */
-			numbers = lappend_int(numbers, 0);
+			/* Just put NULL into this list entry */
 			vars = lappend(vars, NULL);
 			continue;
 		}
@@ -1362,7 +1357,6 @@ make_inh_translation_lists(Relation oldrelation, Relation newrelation,
 		 */
 		if (oldrelation == newrelation)
 		{
-			numbers = lappend_int(numbers, old_attno + 1);
 			vars = lappend(vars, makeVar(newvarno,
 										 (AttrNumber) (old_attno + 1),
 										 atttypid,
@@ -1405,7 +1399,6 @@ make_inh_translation_lists(Relation oldrelation, Relation newrelation,
 			elog(ERROR, "attribute \"%s\" of relation \"%s\" does not match parent's type",
 				 attname, RelationGetRelationName(newrelation));
 
-		numbers = lappend_int(numbers, new_attno + 1);
 		vars = lappend(vars, makeVar(newvarno,
 									 (AttrNumber) (new_attno + 1),
 									 atttypid,
@@ -1413,7 +1406,6 @@ make_inh_translation_lists(Relation oldrelation, Relation newrelation,
 									 0));
 	}
 
-	*col_mappings = numbers;
 	*translated_vars = vars;
 }
 
@@ -1682,70 +1674,6 @@ adjust_relid_set(Relids relids, Index oldrelid, Index newrelid)
 	return relids;
 }
 
-/*
- * adjust_appendrel_attr_needed
- *		Adjust an attr_needed[] array to reference a member rel instead of
- *		the original appendrel
- *
- * oldrel: source of data (we use the attr_needed, min_attr, max_attr fields)
- * appinfo: supplies parent_relid, child_relid, col_mappings
- * new_min_attr, new_max_attr: desired bounds of new attr_needed array
- *
- * The relid sets are adjusted by substituting child_relid for parent_relid.
- * (NOTE: oldrel is not necessarily the parent_relid relation!)  We are also
- * careful to map attribute numbers within the array properly.	User
- * attributes have to be mapped through col_mappings, but system attributes
- * and whole-row references always have the same attno.
- *
- * Returns a palloc'd array with the specified bounds
- */
-Relids *
-adjust_appendrel_attr_needed(RelOptInfo *oldrel, AppendRelInfo *appinfo,
-							 AttrNumber new_min_attr, AttrNumber new_max_attr)
-{
-	Relids	   *new_attr_needed;
-	Index		parent_relid = appinfo->parent_relid;
-	Index		child_relid = appinfo->child_relid;
-	int			parent_attr;
-	ListCell   *lm;
-
-	/* Create empty result array */
-	new_attr_needed = (Relids *)
-		palloc0((new_max_attr - new_min_attr + 1) * sizeof(Relids));
-	/* Process user attributes, with appropriate attno mapping */
-	parent_attr = 1;
-	foreach(lm, appinfo->col_mappings)
-	{
-		int			child_attr = lfirst_int(lm);
-
-		if (child_attr > 0)
-		{
-			Relids		attrneeded;
-
-			Assert(parent_attr <= oldrel->max_attr);
-			Assert(child_attr <= new_max_attr);
-			attrneeded = oldrel->attr_needed[parent_attr - oldrel->min_attr];
-			attrneeded = adjust_relid_set(attrneeded,
-										  parent_relid, child_relid);
-			new_attr_needed[child_attr - new_min_attr] = attrneeded;
-		}
-		parent_attr++;
-	}
-	/* Process system attributes, including whole-row references */
-	Assert(new_min_attr <= oldrel->min_attr);
-	for (parent_attr = oldrel->min_attr; parent_attr <= 0; parent_attr++)
-	{
-		Relids		attrneeded;
-
-		attrneeded = oldrel->attr_needed[parent_attr - oldrel->min_attr];
-		attrneeded = adjust_relid_set(attrneeded,
-									  parent_relid, child_relid);
-		new_attr_needed[parent_attr - new_min_attr] = attrneeded;
-	}
-
-	return new_attr_needed;
-}
-
 /*
  * Adjust the targetlist entries of an inherited UPDATE operation
  *
@@ -1778,24 +1706,24 @@ adjust_inherited_tlist(List *tlist, AppendRelInfo *context)
 	foreach(tl, tlist)
 	{
 		TargetEntry *tle = (TargetEntry *) lfirst(tl);
-		int			newattno;
+		Var		   *childvar;
 
 		if (tle->resjunk)
 			continue;			/* ignore junk items */
 
-		/* Look up the translation of this column */
+		/* Look up the translation of this column: it must be a Var */
 		if (tle->resno <= 0 ||
-			tle->resno > list_length(context->col_mappings))
+			tle->resno > list_length(context->translated_vars))
 			elog(ERROR, "attribute %d of relation \"%s\" does not exist",
 				 tle->resno, get_rel_name(context->parent_reloid));
-		newattno = list_nth_int(context->col_mappings, tle->resno - 1);
-		if (newattno <= 0)
+		childvar = (Var *) list_nth(context->translated_vars, tle->resno - 1);
+		if (childvar == NULL || !IsA(childvar, Var))
 			elog(ERROR, "attribute %d of relation \"%s\" does not exist",
 				 tle->resno, get_rel_name(context->parent_reloid));
 
-		if (tle->resno != newattno)
+		if (tle->resno != childvar->varattno)
 		{
-			tle->resno = newattno;
+			tle->resno = childvar->varattno;
 			changed_it = true;
 		}
 	}

src/include/nodes/relation.h

@@ -7,7 +7,7 @@
  * Portions Copyright (c) 1996-2008, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
- * $PostgreSQL: pgsql/src/include/nodes/relation.h,v 1.163 2008/10/22 20:17:52 tgl Exp $
+ * $PostgreSQL: pgsql/src/include/nodes/relation.h,v 1.164 2008/11/11 18:13:32 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -1239,27 +1239,14 @@ typedef struct AppendRelInfo
 	Oid			parent_reltype; /* OID of parent's composite type */
 	Oid			child_reltype;	/* OID of child's composite type */
 
-	/*
-	 * The N'th element of this list is the integer column number of the child
-	 * column corresponding to the N'th column of the parent. A list element
-	 * is zero if it corresponds to a dropped column of the parent (this is
-	 * only possible for inheritance cases, not UNION ALL).
-	 */
-	List	   *col_mappings;	/* list of child attribute numbers */
-
 	/*
 	 * The N'th element of this list is a Var or expression representing the
 	 * child column corresponding to the N'th column of the parent. This is
 	 * used to translate Vars referencing the parent rel into references to
 	 * the child.  A list element is NULL if it corresponds to a dropped
 	 * column of the parent (this is only possible for inheritance cases, not
-	 * UNION ALL).
-	 *
-	 * This might seem redundant with the col_mappings data, but it is handy
-	 * because flattening of sub-SELECTs that are members of a UNION ALL will
-	 * cause changes in the expressions that need to be substituted for a
-	 * parent Var.	Adjusting this data structure lets us track what really
-	 * needs to be substituted.
+	 * UNION ALL).  The list elements are always simple Vars for inheritance
+	 * cases, but can be arbitrary expressions in UNION ALL cases.
 	 *
 	 * Notice we only store entries for user columns (attno > 0).  Whole-row
 	 * Vars are special-cased, and system columns (attno < 0) need no special

src/include/optimizer/prep.h

@@ -7,7 +7,7 @@
  * Portions Copyright (c) 1996-2008, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
- * $PostgreSQL: pgsql/src/include/optimizer/prep.h,v 1.62 2008/08/17 01:20:00 tgl Exp $
+ * $PostgreSQL: pgsql/src/include/optimizer/prep.h,v 1.63 2008/11/11 18:13:32 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -51,9 +51,4 @@ extern void expand_inherited_tables(PlannerInfo *root);
 
 extern Node *adjust_appendrel_attrs(Node *node, AppendRelInfo *appinfo);
 
-extern Relids *adjust_appendrel_attr_needed(RelOptInfo *oldrel,
-							 AppendRelInfo *appinfo,
-							 AttrNumber new_min_attr,
-							 AttrNumber new_max_attr);
-
 #endif   /* PREP_H */