Remove arbitrary 64K-or-so limit on rangetable size.

Up to now the size of a query's rangetable has been limited by the
constants INNER_VAR et al, which mustn't be equal to any real
rangetable index.  65000 doubtless seemed like enough for anybody,
and it still is orders of magnitude larger than the number of joins
we can realistically handle.  However, we need a rangetable entry
for each child partition that is (or might be) processed by a query.
Queries with a few thousand partitions are getting more realistic,
so that the day when that limit becomes a problem is in sight,
even if it's not here yet.  Hence, let's raise the limit.

Rather than just increase the values of INNER_VAR et al, this patch
adopts the approach of making them small negative values, so that
rangetables could theoretically become as long as INT_MAX.

The bulk of the patch is concerned with changing Var.varno and some
related variables from "Index" (unsigned int) to plain "int".  This
is basically cosmetic, with little actual effect other than to help
debuggers print their values nicely.  As such, I've only bothered
with changing places that could actually see INNER_VAR et al, which
the parser and most of the planner don't.  We do have to be careful
in places that are performing less/greater comparisons on varnos,
but there are very few such places, other than the IS_SPECIAL_VARNO
macro itself.

A notable side effect of this patch is that while it used to be
possible to add INNER_VAR et al to a Bitmapset, that will now
draw an error.  I don't see any likelihood that it wouldn't be a
bug to include these fake varnos in a bitmapset of real varnos,
so I think this is all to the good.

Although this touches outfuncs/readfuncs, I don't think a catversion
bump is required, since stored rules would never contain Vars
with these fake varnos.

Andrey Lepikhov and Tom Lane, after a suggestion by Peter Eisentraut

Discussion: https://postgr.es/m/43c7f2f5-1e27-27aa-8c65-c91859d15190@postgrespro.ru

1 files changed, 14 insertions, 26 deletions

diff --git a/src/backend/optimizer/plan/setrefs.c b/src/backend/optimizer/plan/setrefs.c
index 3d23a2e5ac7..6ccec759bd2 100644
--- a/src/backend/optimizer/plan/setrefs.c
+++ b/src/backend/optimizer/plan/setrefs.c
@@ -31,7 +31,7 @@
 
 typedef struct
 {
-	Index		varno;			/* RT index of Var */
+	int			varno;			/* RT index of Var */
 	AttrNumber	varattno;		/* attr number of Var */
 	AttrNumber	resno;			/* TLE position of Var */
 } tlist_vinfo;
@@ -66,7 +66,7 @@ typedef struct
 {
 	PlannerInfo *root;
 	indexed_tlist *subplan_itlist;
-	Index		newvarno;
+	int			newvarno;
 	int			rtoffset;
 	double		num_exec;
 } fix_upper_expr_context;
@@ -143,15 +143,15 @@ static void set_dummy_tlist_references(Plan *plan, int rtoffset);
 static indexed_tlist *build_tlist_index(List *tlist);
 static Var *search_indexed_tlist_for_var(Var *var,
 										 indexed_tlist *itlist,
-										 Index newvarno,
+										 int newvarno,
 										 int rtoffset);
 static Var *search_indexed_tlist_for_non_var(Expr *node,
 											 indexed_tlist *itlist,
-											 Index newvarno);
+											 int newvarno);
 static Var *search_indexed_tlist_for_sortgroupref(Expr *node,
 												  Index sortgroupref,
 												  indexed_tlist *itlist,
-												  Index newvarno);
+												  int newvarno);
 static List *fix_join_expr(PlannerInfo *root,
 						   List *clauses,
 						   indexed_tlist *outer_itlist,
@@ -163,7 +163,7 @@ static Node *fix_join_expr_mutator(Node *node,
 static Node *fix_upper_expr(PlannerInfo *root,
 							Node *node,
 							indexed_tlist *subplan_itlist,
-							Index newvarno,
+							int newvarno,
 							int rtoffset, double num_exec);
 static Node *fix_upper_expr_mutator(Node *node,
 									fix_upper_expr_context *context);
@@ -506,16 +506,6 @@ add_rte_to_flat_rtable(PlannerGlobal *glob, RangeTblEntry *rte)
 	glob->finalrtable = lappend(glob->finalrtable, newrte);
 
 	/*
-	 * Check for RT index overflow; it's very unlikely, but if it did happen,
-	 * the executor would get confused by varnos that match the special varno
-	 * values.
-	 */
-	if (IS_SPECIAL_VARNO(list_length(glob->finalrtable)))
-		ereport(ERROR,
-				(errcode(ERRCODE_PROGRAM_LIMIT_EXCEEDED),
-				 errmsg("too many range table entries")));
-
-	/*
 	 * If it's a plain relation RTE, add the table to relationOids.
 	 *
 	 * We do this even though the RTE might be unreferenced in the plan tree;
@@ -1947,10 +1937,8 @@ fix_scan_expr_mutator(Node *node, fix_scan_expr_context *context)
 	{
 		CurrentOfExpr *cexpr = (CurrentOfExpr *) copyObject(node);
 
-		Assert(cexpr->cvarno != INNER_VAR);
-		Assert(cexpr->cvarno != OUTER_VAR);
-		if (!IS_SPECIAL_VARNO(cexpr->cvarno))
-			cexpr->cvarno += context->rtoffset;
+		Assert(!IS_SPECIAL_VARNO(cexpr->cvarno));
+		cexpr->cvarno += context->rtoffset;
 		return (Node *) cexpr;
 	}
 	if (IsA(node, PlaceHolderVar))
@@ -2447,7 +2435,7 @@ build_tlist_index(List *tlist)
  * (so nothing other than Vars and PlaceHolderVars can be matched).
  */
 static indexed_tlist *
-build_tlist_index_other_vars(List *tlist, Index ignore_rel)
+build_tlist_index_other_vars(List *tlist, int ignore_rel)
 {
 	indexed_tlist *itlist;
 	tlist_vinfo *vinfo;
@@ -2499,9 +2487,9 @@ build_tlist_index_other_vars(List *tlist, Index ignore_rel)
  */
 static Var *
 search_indexed_tlist_for_var(Var *var, indexed_tlist *itlist,
-							 Index newvarno, int rtoffset)
+							 int newvarno, int rtoffset)
 {
-	Index		varno = var->varno;
+	int			varno = var->varno;
 	AttrNumber	varattno = var->varattno;
 	tlist_vinfo *vinfo;
 	int			i;
@@ -2539,7 +2527,7 @@ search_indexed_tlist_for_var(Var *var, indexed_tlist *itlist,
  */
 static Var *
 search_indexed_tlist_for_non_var(Expr *node,
-								 indexed_tlist *itlist, Index newvarno)
+								 indexed_tlist *itlist, int newvarno)
 {
 	TargetEntry *tle;
 
@@ -2581,7 +2569,7 @@ static Var *
 search_indexed_tlist_for_sortgroupref(Expr *node,
 									  Index sortgroupref,
 									  indexed_tlist *itlist,
-									  Index newvarno)
+									  int newvarno)
 {
 	ListCell   *lc;
 
@@ -2799,7 +2787,7 @@ static Node *
 fix_upper_expr(PlannerInfo *root,
 			   Node *node,
 			   indexed_tlist *subplan_itlist,
-			   Index newvarno,
+			   int newvarno,
 			   int rtoffset,
 			   double num_exec)
 {