Ensure that pg_get_ruledef()'s output matches pg_get_viewdef()'s.

Various cases involving renaming of view columns are handled by having
make_viewdef pass down the view's current relation tupledesc to
get_query_def, which then takes care to use the column names from the
tupledesc for the output column names of the SELECT.  For some reason
though, we'd missed teaching make_ruledef to do similarly when it is
printing an ON SELECT rule, even though this is exactly the same case.
The results from pg_get_ruledef would then be different and arguably wrong.
In particular, this breaks pre-v10 versions of pg_dump, which in some
situations would define views by means of emitting a CREATE RULE ... ON
SELECT command.  Third-party tools might not be happy either.

In passing, clean up some crufty code in make_viewdef; we'd apparently
modernized the equivalent code in make_ruledef somewhere along the way,
and missed this copy.

Per report from Gilles Darold.  Back-patch to all supported versions.

Discussion: https://postgr.es/m/ec05659a-40ff-4510-fc45-ca9d965d0838@dalibo.com

1 files changed, 20 insertions, 5 deletions

diff --git a/src/backend/utils/adt/ruleutils.c b/src/backend/utils/adt/ruleutils.c
index 493ba924a49..d83377d1d88 100644
--- a/src/backend/utils/adt/ruleutils.c
+++ b/src/backend/utils/adt/ruleutils.c
@@ -4590,6 +4590,8 @@ make_ruledef(StringInfo buf, HeapTuple ruletup, TupleDesc rulettc,
 	char	   *ev_qual;
 	char	   *ev_action;
 	List	   *actions = NIL;
+	Relation	ev_relation;
+	TupleDesc	viewResultDesc = NULL;
 	int			fno;
 	Datum		dat;
 	bool		isnull;
@@ -4626,6 +4628,8 @@ make_ruledef(StringInfo buf, HeapTuple ruletup, TupleDesc rulettc,
 	if (ev_action != NULL)
 		actions = (List *) stringToNode(ev_action);
 
+	ev_relation = heap_open(ev_class, AccessShareLock);
+
 	/*
 	 * Build the rules definition text
 	 */
@@ -4642,6 +4646,7 @@ make_ruledef(StringInfo buf, HeapTuple ruletup, TupleDesc rulettc,
 	{
 		case '1':
 			appendStringInfoString(buf, "SELECT");
+			viewResultDesc = RelationGetDescr(ev_relation);
 			break;
 
 		case '2':
@@ -4731,7 +4736,7 @@ make_ruledef(StringInfo buf, HeapTuple ruletup, TupleDesc rulettc,
 		foreach(action, actions)
 		{
 			query = (Query *) lfirst(action);
-			get_query_def(query, buf, NIL, NULL,
+			get_query_def(query, buf, NIL, viewResultDesc,
 						  prettyFlags, WRAP_COLUMN_DEFAULT, 0);
 			if (prettyFlags)
 				appendStringInfoString(buf, ";\n");
@@ -4749,10 +4754,12 @@ make_ruledef(StringInfo buf, HeapTuple ruletup, TupleDesc rulettc,
 		Query	   *query;
 
 		query = (Query *) linitial(actions);
-		get_query_def(query, buf, NIL, NULL,
+		get_query_def(query, buf, NIL, viewResultDesc,
 					  prettyFlags, WRAP_COLUMN_DEFAULT, 0);
 		appendStringInfoChar(buf, ';');
 	}
+
+	heap_close(ev_relation, AccessShareLock);
 }
 
 
@@ -4774,20 +4781,28 @@ make_viewdef(StringInfo buf, HeapTuple ruletup, TupleDesc rulettc,
 	List	   *actions = NIL;
 	Relation	ev_relation;
 	int			fno;
+	Datum		dat;
 	bool		isnull;
 
 	/*
 	 * Get the attribute values from the rules tuple
 	 */
 	fno = SPI_fnumber(rulettc, "ev_type");
-	ev_type = (char) SPI_getbinval(ruletup, rulettc, fno, &isnull);
+	dat = SPI_getbinval(ruletup, rulettc, fno, &isnull);
+	Assert(!isnull);
+	ev_type = DatumGetChar(dat);
 
 	fno = SPI_fnumber(rulettc, "ev_class");
-	ev_class = (Oid) SPI_getbinval(ruletup, rulettc, fno, &isnull);
+	dat = SPI_getbinval(ruletup, rulettc, fno, &isnull);
+	Assert(!isnull);
+	ev_class = DatumGetObjectId(dat);
 
 	fno = SPI_fnumber(rulettc, "is_instead");
-	is_instead = (bool) SPI_getbinval(ruletup, rulettc, fno, &isnull);
+	dat = SPI_getbinval(ruletup, rulettc, fno, &isnull);
+	Assert(!isnull);
+	is_instead = DatumGetBool(dat);
 
+	/* these could be nulls */
 	fno = SPI_fnumber(rulettc, "ev_qual");
 	ev_qual = SPI_getvalue(ruletup, rulettc, fno);