Add display of sort keys to the default EXPLAIN output.

src/backend/commands/explain.c

@@ -5,7 +5,7 @@
  * Portions Copyright (c) 1996-2001, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994-5, Regents of the University of California
  *
- * $Header: /cvsroot/pgsql/src/backend/commands/explain.c,v 1.77 2002/05/12 20:10:02 tgl Exp $
+ * $Header: /cvsroot/pgsql/src/backend/commands/explain.c,v 1.78 2002/05/18 21:38:40 tgl Exp $
  *
  */
 
@@ -56,6 +56,8 @@ 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, const char *qlabel,
+						   StringInfo str, int indent, ExplainState *es);
 static Node *make_ors_ands_explicit(List *orclauses);
 static TextOutputState *begin_text_output(CommandDest dest, char *title);
 static void do_text_output(TextOutputState *tstate, char *aline);
@@ -410,7 +412,7 @@ explain_outNode(StringInfo str, Plan *plan, Plan *outer_plan,
 	}
 	appendStringInfo(str, "\n");
 
-	/* quals */
+	/* quals, sort keys, etc */
 	switch (nodeTag(plan))
 	{
 		case T_IndexScan:
@@ -495,6 +497,11 @@ explain_outNode(StringInfo str, Plan *plan, Plan *outer_plan,
 							"", 0, NULL,
 							str, indent, es);
 			break;
+		case T_Sort:
+			show_sort_keys(plan->targetlist, ((Sort *) plan)->keycount,
+						   "Sort Key",
+						   str, indent, es);
+			break;
 		case T_Result:
 			show_upper_qual((List *) ((Result *) plan)->resconstantqual,
 							"One-Time Filter",
@@ -731,6 +738,60 @@ show_upper_qual(List *qual, const char *qlabel,
 	appendStringInfo(str, "  %s: %s\n", qlabel, exprstr);
 }
 
+/*
+ * Show the sort keys for a Sort node.
+ */
+static void
+show_sort_keys(List *tlist, int nkeys, const char *qlabel,
+			   StringInfo str, int indent, ExplainState *es)
+{
+	List	   *context;
+	bool		useprefix;
+	int			keyno;
+	List	   *tl;
+	char	   *exprstr;
+	int			i;
+
+	if (nkeys <= 0)
+		return;
+
+	for (i = 0; i < indent; i++)
+		appendStringInfo(str, "  ");
+	appendStringInfo(str, "  %s: ", qlabel);
+
+	/*
+	 * In this routine we expect that the plan node's tlist has not been
+	 * processed by set_plan_references(), so any Vars will contain valid
+	 * varnos referencing the actual rtable.
+	 */
+	context = deparse_context_from_rtable(es->rtable);
+	useprefix = length(es->rtable) > 1;
+
+	for (keyno = 1; keyno <= nkeys; keyno++)
+	{
+		/* find key expression in tlist */
+		foreach(tl, tlist)
+		{
+			TargetEntry *target = (TargetEntry *) lfirst(tl);
+
+			if (target->resdom->reskey == keyno)
+			{
+				/* Deparse the expression */
+				exprstr = deparse_expression(target->expr, context, useprefix);
+				/* And add to str */
+				if (keyno > 1)
+					appendStringInfo(str, ", ");
+				appendStringInfo(str, "%s", exprstr);
+				break;
+			}
+		}
+		if (tl == NIL)
+			elog(ERROR, "show_sort_keys: no tlist entry for key %d", keyno);
+	}
+
+	appendStringInfo(str, "\n");
+}
+
 /*
  * Indexscan qual lists have an implicit OR-of-ANDs structure.  Make it
  * explicit so deparsing works properly.

src/backend/utils/adt/ruleutils.c

@@ -3,7 +3,7 @@
  *				back to source text
  *
  * IDENTIFICATION
- *	  $Header: /cvsroot/pgsql/src/backend/utils/adt/ruleutils.c,v 1.105 2002/05/17 01:19:18 tgl Exp $
+ *	  $Header: /cvsroot/pgsql/src/backend/utils/adt/ruleutils.c,v 1.106 2002/05/18 21:38:40 tgl Exp $
  *
  *	  This software is copyrighted by Jan Wieck - Hamburg.
  *
@@ -779,6 +779,27 @@ deparse_context_for_subplan(const char *name, List *tlist,
 	return (Node *) rte;
 }
 
+/*
+ * deparse_context_from_rtable	- Build deparse context given a rangetable
+ *
+ * This is suitable for deparsing expressions that refer to only a single
+ * level of variables (no outer-reference Vars).
+ */
+List *
+deparse_context_from_rtable(List *rtable)
+{
+	deparse_namespace *dpns;
+
+	dpns = (deparse_namespace *) palloc(sizeof(deparse_namespace));
+
+	dpns->rtable = rtable;
+	dpns->outer_varno = dpns->inner_varno = 0;
+	dpns->outer_rte = dpns->inner_rte = NULL;
+
+	/* Return a one-deep namespace stack */
+	return makeList1(dpns);
+}
+
 /* ----------
  * make_ruledef			- reconstruct the CREATE RULE command
  *				  for a given pg_rewrite tuple

src/include/utils/builtins.h

@@ -7,7 +7,7 @@
  * Portions Copyright (c) 1996-2001, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
- * $Id: builtins.h,v 1.181 2002/05/12 20:10:05 tgl Exp $
+ * $Id: builtins.h,v 1.182 2002/05/18 21:38:41 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -357,6 +357,7 @@ extern List *deparse_context_for_plan(int outer_varno, Node *outercontext,
 extern Node *deparse_context_for_rte(RangeTblEntry *rte);
 extern Node *deparse_context_for_subplan(const char *name, List *tlist,
 										 List *rtable);
+extern List *deparse_context_from_rtable(List *rtable);
 extern const char *quote_identifier(const char *ident);
 extern char *quote_qualified_identifier(const char *namespace,
 										const char *ident);