Fix EXPLAIN so that it can drill down through multiple levels of subplan

when trying to locate the referent of a RECORD variable.  This fixes the
'record type has not been registered' failure reported by Stefan
Kaltenbrunner about a month ago.  A side effect of the way I chose to
fix it is that most variable references in join conditions will now be
properly labeled with the variable's source table name, instead of the
not-too-helpful 'outer' or 'inner' we used to use.

src/backend/commands/explain.c

@@ -7,7 +7,7 @@
  * Portions Copyright (c) 1994-5, Regents of the University of California
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/commands/explain.c,v 1.146 2006/03/05 15:58:24 momjian Exp $
+ *	  $PostgreSQL: pgsql/src/backend/commands/explain.c,v 1.147 2006/04/08 18:49:52 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -58,7 +58,7 @@ static void show_upper_qual(List *qual, const char *qlabel,
 				const char *outer_name, int outer_varno, Plan *outer_plan,
 				const char *inner_name, int inner_varno, Plan *inner_plan,
 				StringInfo str, int indent, ExplainState *es);
-static void show_sort_keys(List *tlist, int nkeys, AttrNumber *keycols,
+static void show_sort_keys(Plan *sortplan, int nkeys, AttrNumber *keycols,
 			   const char *qlabel,
 			   StringInfo str, int indent, ExplainState *es);
 
@@ -815,7 +815,7 @@ explain_outNode(StringInfo str,
 							str, indent, es);
 			break;
 		case T_Sort:
-			show_sort_keys(plan->targetlist,
+			show_sort_keys(plan,
 						   ((Sort *) plan)->numCols,
 						   ((Sort *) plan)->sortColIdx,
 						   "Sort Key",
@@ -1030,8 +1030,6 @@ show_scan_qual(List *qual, const char *qlabel,
 			   int scanrelid, Plan *outer_plan,
 			   StringInfo str, int indent, ExplainState *es)
 {
-	RangeTblEntry *rte;
-	Node	   *scancontext;
 	Node	   *outercontext;
 	List	   *context;
 	Node	   *node;
@@ -1045,11 +1043,6 @@ show_scan_qual(List *qual, const char *qlabel,
 	/* Convert AND list to explicit AND */
 	node = (Node *) make_ands_explicit(qual);
 
-	/* Generate deparse context */
-	Assert(scanrelid > 0 && scanrelid <= list_length(es->rtable));
-	rte = rt_fetch(scanrelid, es->rtable);
-	scancontext = deparse_context_for_rte(rte);
-
 	/*
 	 * If we have an outer plan that is referenced by the qual, add it to the
 	 * deparse context.  If not, don't (so that we don't force prefixes
@@ -1061,8 +1054,7 @@ show_scan_qual(List *qual, const char *qlabel,
 
 		if (bms_is_member(OUTER, varnos))
 			outercontext = deparse_context_for_subplan("outer",
-													   outer_plan->targetlist,
-													   es->rtable);
+													   (Node *) outer_plan);
 		else
 			outercontext = NULL;
 		bms_free(varnos);
@@ -1070,9 +1062,9 @@ show_scan_qual(List *qual, const char *qlabel,
 	else
 		outercontext = NULL;
 
-	context = deparse_context_for_plan(scanrelid, scancontext,
-									   OUTER, outercontext,
-									   NIL);
+	context = deparse_context_for_plan(OUTER, outercontext,
+									   0, NULL,
+									   es->rtable);
 
 	/* Deparse the expression */
 	exprstr = deparse_expression(node, context, (outercontext != NULL), false);
@@ -1106,19 +1098,17 @@ show_upper_qual(List *qual, const char *qlabel,
 	/* Generate deparse context */
 	if (outer_plan)
 		outercontext = deparse_context_for_subplan(outer_name,
-												   outer_plan->targetlist,
-												   es->rtable);
+												   (Node *) outer_plan);
 	else
 		outercontext = NULL;
 	if (inner_plan)
 		innercontext = deparse_context_for_subplan(inner_name,
-												   inner_plan->targetlist,
-												   es->rtable);
+												   (Node *) inner_plan);
 	else
 		innercontext = NULL;
 	context = deparse_context_for_plan(outer_varno, outercontext,
 									   inner_varno, innercontext,
-									   NIL);
+									   es->rtable);
 
 	/* Deparse the expression */
 	node = (Node *) make_ands_explicit(qual);
@@ -1134,7 +1124,7 @@ show_upper_qual(List *qual, const char *qlabel,
  * Show the sort keys for a Sort node.
  */
 static void
-show_sort_keys(List *tlist, int nkeys, AttrNumber *keycols,
+show_sort_keys(Plan *sortplan, int nkeys, AttrNumber *keycols,
 			   const char *qlabel,
 			   StringInfo str, int indent, ExplainState *es)
 {
@@ -1159,17 +1149,16 @@ show_sort_keys(List *tlist, int nkeys, AttrNumber *keycols,
 	 * looking at a dummy tlist generated by prepunion.c; if there are Vars
 	 * with zero varno, use the tlist itself to determine their names.
 	 */
-	varnos = pull_varnos((Node *) tlist);
+	varnos = pull_varnos((Node *) sortplan->targetlist);
 	if (bms_is_member(0, varnos))
 	{
 		Node	   *outercontext;
 
 		outercontext = deparse_context_for_subplan("sort",
-												   tlist,
-												   es->rtable);
+												   (Node *) sortplan);
 		context = deparse_context_for_plan(0, outercontext,
 										   0, NULL,
-										   NIL);
+										   es->rtable);
 		useprefix = false;
 	}
 	else
@@ -1185,7 +1174,7 @@ show_sort_keys(List *tlist, int nkeys, AttrNumber *keycols,
 	{
 		/* find key expression in tlist */
 		AttrNumber	keyresno = keycols[keyno];
-		TargetEntry *target = get_tle_by_resno(tlist, keyresno);
+		TargetEntry *target = get_tle_by_resno(sortplan->targetlist, keyresno);
 
 		if (!target)
 			elog(ERROR, "no tlist entry for key %d", keyresno);

src/backend/utils/adt/ruleutils.c

@@ -2,7 +2,7 @@
  * ruleutils.c	- Functions to convert stored expressions/querytrees
  *				back to source text
  *
- *	  $PostgreSQL: pgsql/src/backend/utils/adt/ruleutils.c,v 1.218 2006/04/04 19:35:36 tgl Exp $
+ *	  $PostgreSQL: pgsql/src/backend/utils/adt/ruleutils.c,v 1.219 2006/04/08 18:49:52 tgl Exp $
  **********************************************************************/
 
 #include "postgres.h"
@@ -89,7 +89,7 @@ typedef struct
  * The rangetable is the list of actual RTEs from the query tree.
  *
  * For deparsing plan trees, we allow two special RTE entries that are not
- * part of the rtable list (mainly because they don't have consecutively
+ * part of the rtable list (partly because they don't have consecutively
  * allocated varnos).
  */
 typedef struct
@@ -1395,15 +1395,13 @@ deparse_context_for(const char *aliasname, Oid relid)
 /*
  * deparse_context_for_plan		- Build deparse context for a plan node
  *
- * We assume we are dealing with an upper-level plan node having either
- * one or two referenceable children (pass innercontext = NULL if only one).
- * The passed-in Nodes should be made using deparse_context_for_subplan
- * and/or deparse_context_for_relation.  The resulting context will work
- * for deparsing quals, tlists, etc of the plan node.
+ * The plan node may contain references to one or two subplans or outer
+ * join plan nodes.  For these, pass the varno used plus a context node
+ * made with deparse_context_for_subplan.  (Pass 0/NULL for unused inputs.)
  *
- * An rtable list can also be passed in case plain Vars might be seen.
- * This is not needed for true upper-level expressions, but is helpful for
- * Sort nodes and similar cases with slightly bogus targetlists.
+ * The plan's rangetable list must also be passed.  We actually prefer to use
+ * the rangetable to resolve simple Vars, but the subplan inputs are needed
+ * for Vars that reference expressions computed in subplan target lists.
  */
 List *
 deparse_context_for_plan(int outer_varno, Node *outercontext,
@@ -1424,90 +1422,32 @@ deparse_context_for_plan(int outer_varno, Node *outercontext,
 	return list_make1(dpns);
 }
 
-/*
- * deparse_context_for_rte		- Build deparse context for 1 relation
- *
- * Helper routine to build one of the inputs for deparse_context_for_plan.
- *
- * The returned node is actually the given RangeTblEntry, but we declare it
- * as just Node to discourage callers from assuming anything.
- */
-Node *
-deparse_context_for_rte(RangeTblEntry *rte)
-{
-	return (Node *) rte;
-}
-
 /*
  * deparse_context_for_subplan	- Build deparse context for a plan node
  *
  * Helper routine to build one of the inputs for deparse_context_for_plan.
- * Pass the tlist of the subplan node, plus the query rangetable.
+ * Pass the name to be used to reference the subplan, plus the Plan node.
+ * (subplan really ought to be declared as "Plan *", but we use "Node *"
+ * to avoid having to include plannodes.h in builtins.h.)
  *
  * The returned node is actually a RangeTblEntry, but we declare it as just
  * Node to discourage callers from assuming anything.
  */
 Node *
-deparse_context_for_subplan(const char *name, List *tlist,
-							List *rtable)
+deparse_context_for_subplan(const char *name, Node *subplan)
 {
 	RangeTblEntry *rte = makeNode(RangeTblEntry);
-	List	   *attrs = NIL;
-	int			nattrs = 0;
-	int			rtablelength = list_length(rtable);
-	ListCell   *tl;
-	char		buf[32];
-
-	foreach(tl, tlist)
-	{
-		TargetEntry *tle = lfirst(tl);
-
-		nattrs++;
-		Assert(tle->resno == nattrs);
-		if (tle->resname)
-		{
-			attrs = lappend(attrs, makeString(tle->resname));
-			continue;
-		}
-		if (tle->expr && IsA(tle->expr, Var))
-		{
-			Var		   *var = (Var *) tle->expr;
-
-			/* varno/varattno won't be any good, but varnoold might be */
-			if (var->varnoold > 0 && var->varnoold <= rtablelength)
-			{
-				RangeTblEntry *varrte = rt_fetch(var->varnoold, rtable);
-				AttrNumber	varattnum = var->varoattno;
-
-				/* need this test in case it's referencing a resjunk col */
-				if (varattnum <= list_length(varrte->eref->colnames))
-				{
-					char	   *varname;
-
-					varname = get_rte_attribute_name(varrte, varattnum);
-					attrs = lappend(attrs, makeString(varname));
-					continue;
-				}
-			}
-		}
-		/* Fallback if can't get name */
-		snprintf(buf, sizeof(buf), "?column%d?", tle->resno);
-		attrs = lappend(attrs, makeString(pstrdup(buf)));
-	}
 
 	/*
-	 * We create an RTE_SPECIAL RangeTblEntry, and store the given tlist
-	 * in its funccoltypes field.  This is a hack to make the tlist available
-	 * to get_name_for_var_field().  RTE_SPECIAL nodes shouldn't appear in
+	 * We create an RTE_SPECIAL RangeTblEntry, and store the subplan in
+	 * its funcexpr field.  RTE_SPECIAL nodes shouldn't appear in
 	 * deparse contexts otherwise.
-	 *
-	 * XXX this desperately needs redesign, as it fails to handle cases where
-	 * we need to drill down through multiple tlists.
 	 */
 	rte->rtekind = RTE_SPECIAL;
 	rte->relid = InvalidOid;
-	rte->funccoltypes = tlist;
-	rte->eref = makeAlias(name, attrs);
+	rte->funcexpr = subplan;
+	rte->alias = NULL;
+	rte->eref = makeAlias(name, NIL);
 	rte->inh = false;
 	rte->inFromCl = true;
 
@@ -2452,17 +2392,24 @@ get_utility_query_def(Query *query, deparse_context *context)
 /*
  * Get the RTE referenced by a (possibly nonlocal) Var.
  *
+ * The appropriate attribute number is stored into *attno
+ * (do not assume that var->varattno is what to use).
+ *
  * In some cases (currently only when recursing into an unnamed join)
  * the Var's varlevelsup has to be interpreted with respect to a context
  * above the current one; levelsup indicates the offset.
  */
 static RangeTblEntry *
-get_rte_for_var(Var *var, int levelsup, deparse_context *context)
+get_rte_for_var(Var *var, int levelsup, deparse_context *context,
+				AttrNumber *attno)
 {
 	RangeTblEntry *rte;
 	int			netlevelsup;
 	deparse_namespace *dpns;
 
+	/* default assumption */
+	*attno = var->varattno;
+
 	/* Find appropriate nesting depth */
 	netlevelsup = var->varlevelsup + levelsup;
 	if (netlevelsup >= list_length(context->namespaces))
@@ -2471,9 +2418,20 @@ get_rte_for_var(Var *var, int levelsup, deparse_context *context)
 	dpns = (deparse_namespace *) list_nth(context->namespaces,
 										  netlevelsup);
 
-	/* Find the relevant RTE */
+	/*
+	 * Try to find the relevant RTE in this rtable.  In a plan tree, it's
+	 * likely that varno is OUTER, INNER, or 0, in which case we try to
+	 * use varnoold instead.  If the Var references an expression computed
+	 * by a subplan, varnoold will be 0, and we fall back to looking at the
+	 * special subplan RTEs.
+	 */
 	if (var->varno >= 1 && var->varno <= list_length(dpns->rtable))
 		rte = rt_fetch(var->varno, dpns->rtable);
+	else if (var->varnoold >= 1 && var->varnoold <= list_length(dpns->rtable))
+	{
+		rte = rt_fetch(var->varnoold, dpns->rtable);
+		*attno = var->varoattno;
+	}
 	else if (var->varno == dpns->outer_varno)
 		rte = dpns->outer_rte;
 	else if (var->varno == dpns->inner_varno)
@@ -2509,9 +2467,10 @@ get_names_for_var(Var *var, int levelsup, deparse_context *context,
 				  char **schemaname, char **refname, char **attname)
 {
 	RangeTblEntry *rte;
+	AttrNumber	attnum;
 
 	/* Find appropriate RTE */
-	rte = get_rte_for_var(var, levelsup, context);
+	rte = get_rte_for_var(var, levelsup, context, &attnum);
 
 	/* Emit results */
 	*schemaname = NULL;			/* default assumptions */
@@ -2543,12 +2502,11 @@ get_names_for_var(Var *var, int levelsup, deparse_context *context,
 			 * variable name (this can only happen with columns that were
 			 * merged by USING or NATURAL clauses).
 			 */
-			if (var->varattno > 0)
+			if (attnum > 0)
 			{
 				Var		   *aliasvar;
 
-				aliasvar = (Var *) list_nth(rte->joinaliasvars,
-											var->varattno - 1);
+				aliasvar = (Var *) list_nth(rte->joinaliasvars, attnum - 1);
 				if (IsA(aliasvar, Var))
 				{
 					get_names_for_var(aliasvar,
@@ -2560,12 +2518,36 @@ get_names_for_var(Var *var, int levelsup, deparse_context *context,
 			/* Unnamed join has neither schemaname nor refname */
 			*refname = NULL;
 		}
+		else if (rte->rtekind == RTE_SPECIAL)
+		{
+			/*
+			 * This case occurs during EXPLAIN when we are looking at a
+			 * deparse context node set up by deparse_context_for_subplan().
+			 * If the subplan tlist provides a name, use it, but usually
+			 * we'll end up with "?columnN?".
+			 */
+			List   *tlist = ((Plan *) rte->funcexpr)->targetlist;
+			TargetEntry *tle = get_tle_by_resno(tlist, attnum);
+
+			if (tle && tle->resname)
+			{
+				*attname = tle->resname;
+			}
+			else
+			{
+				char	buf[32];
+
+				snprintf(buf, sizeof(buf), "?column%d?", attnum);
+				*attname = pstrdup(buf);
+			}
+			return;
+		}
 	}
 
-	if (var->varattno == InvalidAttrNumber)
+	if (attnum == InvalidAttrNumber)
 		*attname = NULL;
 	else
-		*attname = get_rte_attribute_name(rte, var->varattno);
+		*attname = get_rte_attribute_name(rte, attnum);
 }
 
 
@@ -2599,9 +2581,7 @@ get_name_for_var_field(Var *var, int fieldno,
 	Assert(var->vartype == RECORDOID);
 
 	/* Find appropriate RTE */
-	rte = get_rte_for_var(var, levelsup, context);
-
-	attnum = var->varattno;
+	rte = get_rte_for_var(var, levelsup, context, &attnum);
 
 	if (attnum == InvalidAttrNumber)
 	{
@@ -2675,18 +2655,37 @@ get_name_for_var_field(Var *var, int fieldno,
 			 */
 			break;
 		case RTE_SPECIAL:
-			/*
-			 * This case occurs during EXPLAIN when we are looking at a
-			 * deparse context node set up by deparse_context_for_subplan().
-			 * Look into the subplan's target list to get the referenced
-			 * expression, and then pass it to get_expr_result_type().
-			 */
-			if (rte->funccoltypes)
 			{
-				TargetEntry *ste = get_tle_by_resno(rte->funccoltypes, attnum);
+				/*
+				 * We are looking at a deparse context node set up by
+				 * deparse_context_for_subplan().  The Var must refer to an
+				 * expression computed by this subplan (or possibly one of its
+				 * inputs), rather than any simple attribute of an RTE entry.
+				 * Look into the subplan's target list to get the referenced
+				 * expression, digging down as far as needed to find something
+				 * that's not a Var, and then pass it to
+				 * get_expr_result_type().
+				 */
+				Plan *subplan = (Plan *) rte->funcexpr;
 
-				if (ste != NULL)
+				for (;;)
+				{
+					TargetEntry *ste;
+
+					ste = get_tle_by_resno(subplan->targetlist,
+										   ((Var *) expr)->varattno);
+					if (!ste || !ste->expr)
+						break;
 					expr = (Node *) ste->expr;
+					if (!IsA(expr, Var))
+						break;
+					if (((Var *) expr)->varno == INNER)
+						subplan = innerPlan(subplan);
+					else
+						subplan = outerPlan(subplan);
+					if (!subplan)
+						break;
+				}
 			}
 			break;
 	}

src/include/utils/builtins.h

@@ -7,7 +7,7 @@
  * Portions Copyright (c) 1996-2006, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
- * $PostgreSQL: pgsql/src/include/utils/builtins.h,v 1.278 2006/04/05 22:11:57 tgl Exp $
+ * $PostgreSQL: pgsql/src/include/utils/builtins.h,v 1.279 2006/04/08 18:49:52 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -526,9 +526,7 @@ extern List *deparse_context_for(const char *aliasname, Oid relid);
 extern List *deparse_context_for_plan(int outer_varno, Node *outercontext,
 						 int inner_varno, Node *innercontext,
 						 List *rtable);
-extern Node *deparse_context_for_rte(RangeTblEntry *rte);
-extern Node *deparse_context_for_subplan(const char *name, List *tlist,
-							List *rtable);
+extern Node *deparse_context_for_subplan(const char *name, Node *subplan);
 extern const char *quote_identifier(const char *ident);
 extern char *quote_qualified_identifier(const char *namespace,
 						   const char *ident);