Refactor parser's generation of Var nodes.

Instead of passing around a pointer to the RangeTblEntry that
provides the desired column, pass a pointer to the associated
ParseNamespaceItem.  The RTE is trivially reachable from the nsitem,
and having the ParseNamespaceItem allows access to additional
information.  As proof of concept for that, add the rangetable index
to ParseNamespaceItem, and use that to get rid of RTERangeTablePosn
searches.

(I have in mind to teach the parser to generate some different
representation for Vars that are nullable by outer joins, and
keeping the necessary information in ParseNamespaceItems seems
like a reasonable approach to that.  But whether that ever
happens or not, this seems like good cleanup.)

Also refactor the code around scanRTEForColumn so that the
"fuzzy match" stuff does not leak out of parse_relation.c.

Discussion: https://postgr.es/m/26144.1576858373@sss.pgh.pa.us

1 files changed, 42 insertions, 43 deletions

diff --git a/src/backend/parser/parse_target.c b/src/backend/parser/parse_target.c
index 30d419e087a..46fe6c60551 100644
--- a/src/backend/parser/parse_target.c
+++ b/src/backend/parser/parse_target.c
@@ -62,8 +62,9 @@ static List *ExpandColumnRefStar(ParseState *pstate, ColumnRef *cref,
 static List *ExpandAllTables(ParseState *pstate, int location);
 static List *ExpandIndirectionStar(ParseState *pstate, A_Indirection *ind,
 								   bool make_target_entry, ParseExprKind exprKind);
-static List *ExpandSingleTable(ParseState *pstate, RangeTblEntry *rte,
-							   int location, bool make_target_entry);
+static List *ExpandSingleTable(ParseState *pstate, ParseNamespaceItem *nsitem,
+							   int sublevels_up, int location,
+							   bool make_target_entry);
 static List *ExpandRowReference(ParseState *pstate, Node *expr,
 								bool make_target_entry);
 static int	FigureColnameInternal(Node *node, char **name);
@@ -548,10 +549,13 @@ transformAssignedExpr(ParseState *pstate,
 			/*
 			 * Build a Var for the column to be updated.
 			 */
-			colVar = (Node *) make_var(pstate,
-									   pstate->p_target_rangetblentry,
-									   attrno,
-									   location);
+			Var		   *var;
+
+			var = makeVar(pstate->p_target_rtindex, attrno,
+						  attrtype, attrtypmod, attrcollation, 0);
+			var->location = location;
+
+			colVar = (Node *) var;
 		}
 
 		expr = (Expr *)
@@ -1127,7 +1131,7 @@ ExpandColumnRefStar(ParseState *pstate, ColumnRef *cref,
 		 */
 		char	   *nspname = NULL;
 		char	   *relname = NULL;
-		RangeTblEntry *rte = NULL;
+		ParseNamespaceItem *nsitem = NULL;
 		int			levels_up;
 		enum
 		{
@@ -1153,16 +1157,16 @@ ExpandColumnRefStar(ParseState *pstate, ColumnRef *cref,
 		{
 			case 2:
 				relname = strVal(linitial(fields));
-				rte = refnameRangeTblEntry(pstate, nspname, relname,
-										   cref->location,
-										   &levels_up);
+				nsitem = refnameNamespaceItem(pstate, nspname, relname,
+											  cref->location,
+											  &levels_up);
 				break;
 			case 3:
 				nspname = strVal(linitial(fields));
 				relname = strVal(lsecond(fields));
-				rte = refnameRangeTblEntry(pstate, nspname, relname,
-										   cref->location,
-										   &levels_up);
+				nsitem = refnameNamespaceItem(pstate, nspname, relname,
+											  cref->location,
+											  &levels_up);
 				break;
 			case 4:
 				{
@@ -1178,9 +1182,9 @@ ExpandColumnRefStar(ParseState *pstate, ColumnRef *cref,
 					}
 					nspname = strVal(lsecond(fields));
 					relname = strVal(lthird(fields));
-					rte = refnameRangeTblEntry(pstate, nspname, relname,
-											   cref->location,
-											   &levels_up);
+					nsitem = refnameNamespaceItem(pstate, nspname, relname,
+												  cref->location,
+												  &levels_up);
 					break;
 				}
 			default:
@@ -1193,17 +1197,19 @@ ExpandColumnRefStar(ParseState *pstate, ColumnRef *cref,
 		 * bit by passing the RangeTblEntry, not a Var, as the planned
 		 * translation.  (A single Var wouldn't be strictly correct anyway.
 		 * This convention allows hooks that really care to know what is
-		 * happening.)
+		 * happening.  It might be better to pass the nsitem, but we'd have to
+		 * promote that struct to a full-fledged Node type so that callees
+		 * could identify its type.)
 		 */
 		if (pstate->p_post_columnref_hook != NULL)
 		{
 			Node	   *node;
 
 			node = pstate->p_post_columnref_hook(pstate, cref,
-												 (Node *) rte);
+												 (Node *) (nsitem ? nsitem->p_rte : NULL));
 			if (node != NULL)
 			{
-				if (rte != NULL)
+				if (nsitem != NULL)
 					ereport(ERROR,
 							(errcode(ERRCODE_AMBIGUOUS_COLUMN),
 							 errmsg("column reference \"%s\" is ambiguous",
@@ -1216,7 +1222,7 @@ ExpandColumnRefStar(ParseState *pstate, ColumnRef *cref,
 		/*
 		 * Throw error if no translation found.
 		 */
-		if (rte == NULL)
+		if (nsitem == NULL)
 		{
 			switch (crserr)
 			{
@@ -1242,9 +1248,10 @@ ExpandColumnRefStar(ParseState *pstate, ColumnRef *cref,
 		}
 
 		/*
-		 * OK, expand the RTE into fields.
+		 * OK, expand the nsitem into fields.
 		 */
-		return ExpandSingleTable(pstate, rte, cref->location, make_target_entry);
+		return ExpandSingleTable(pstate, nsitem, levels_up, cref->location,
+								 make_target_entry);
 	}
 }
 
@@ -1269,7 +1276,6 @@ ExpandAllTables(ParseState *pstate, int location)
 	foreach(l, pstate->p_namespace)
 	{
 		ParseNamespaceItem *nsitem = (ParseNamespaceItem *) lfirst(l);
-		RangeTblEntry *rte = nsitem->p_rte;
 
 		/* Ignore table-only items */
 		if (!nsitem->p_cols_visible)
@@ -1280,12 +1286,10 @@ ExpandAllTables(ParseState *pstate, int location)
 		found_table = true;
 
 		target = list_concat(target,
-							 expandRelAttrs(pstate,
-											rte,
-											RTERangeTablePosn(pstate, rte,
-															  NULL),
-											0,
-											location));
+							 expandNSItemAttrs(pstate,
+											   nsitem,
+											   0,
+											   location));
 	}
 
 	/*
@@ -1341,26 +1345,21 @@ ExpandIndirectionStar(ParseState *pstate, A_Indirection *ind,
  * The referenced columns are marked as requiring SELECT access.
  */
 static List *
-ExpandSingleTable(ParseState *pstate, RangeTblEntry *rte,
-				  int location, bool make_target_entry)
+ExpandSingleTable(ParseState *pstate, ParseNamespaceItem *nsitem,
+				  int sublevels_up, int location, bool make_target_entry)
 {
-	int			sublevels_up;
-	int			rtindex;
-
-	rtindex = RTERangeTablePosn(pstate, rte, &sublevels_up);
-
 	if (make_target_entry)
 	{
-		/* expandRelAttrs handles permissions marking */
-		return expandRelAttrs(pstate, rte, rtindex, sublevels_up,
-							  location);
+		/* expandNSItemAttrs handles permissions marking */
+		return expandNSItemAttrs(pstate, nsitem, sublevels_up, location);
 	}
 	else
 	{
+		RangeTblEntry *rte = nsitem->p_rte;
 		List	   *vars;
 		ListCell   *l;
 
-		expandRTE(rte, rtindex, sublevels_up, location, false,
+		expandRTE(rte, nsitem->p_rtindex, sublevels_up, location, false,
 				  NULL, &vars);
 
 		/*
@@ -1411,10 +1410,10 @@ ExpandRowReference(ParseState *pstate, Node *expr,
 		((Var *) expr)->varattno == InvalidAttrNumber)
 	{
 		Var		   *var = (Var *) expr;
-		RangeTblEntry *rte;
+		ParseNamespaceItem *nsitem;
 
-		rte = GetRTEByRangeTablePosn(pstate, var->varno, var->varlevelsup);
-		return ExpandSingleTable(pstate, rte, var->location, make_target_entry);
+		nsitem = GetNSItemByRangeTablePosn(pstate, var->varno, var->varlevelsup);
+		return ExpandSingleTable(pstate, nsitem, var->varlevelsup, var->location, make_target_entry);
 	}
 
 	/*